HIGH STRENGTH ALUMINUM ALLOYS FOR LOW PRESSURE DIE CASTING AND GRAVITY CASTING

Abstract

Methods of casting lightweight, high-strength aluminum cast structural components are provided wherein the casting is accomplished by low-pressure die casting or gravity casting. The aluminum cast structural component is preferably composed of an aluminum-based alloy comprising silicon at ≥about 4 to ≥about 7 wt. %; iron at ≥about 0.15 wt. %; manganese at ≥about 0.5 wt. %; chromium at ≥about 0.15 to ≥about 0.5 wt. %; magnesium at ≥about 0.8 wt. %; zinc at ≥about 0.01 wt. %; titanium at ≥about 0.05 to ≥about 0.15 wt. %; phosphorus at ≥about 0.003 wt. %; strontium at ≥about 0.015 wt. % and a balance of aluminum.

Description

FIELD

The present disclosure relates to methods of casting metal components and more particularly to methods of casting metal components from aluminum-based metal alloy compositions.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.

Aluminum-based alloys are generally classified into two distinct categories: cast and wrought alloys. Both types of alloys are in widespread use throughout many industries, including in the automotive industry. Wrought alloys typically offer greater yield strengths than cast alloys. Cast alloys, however, are generally cheaper to produce than wrought alloys; further, cast alloys offer yield strengths sufficient for many applications. For example, one suitable wrought aluminum alloy, A6061, offers a yield strength of greater than or equal to about 270 to less or equal to than about 310 MPa, whereas a suitable cast aluminum alloy, A356, offers a yield strength of greater than or equal to about 150 to less than or equal to about 180 MPa.

Turning to cast alloys specifically, aluminum-based alloy cast parts can be produced by conventional casting methods which include die-casting, sand casting, permanent and semi-permanent mold casting, plaster-mold casting and investment casting. Cast parts are generally formed by pouring a molten metal into a casting mold or die that provides shape to the molten material as it cools and solidifies. The mold or die is later separated from the part after solidification.

While many cast alloys offer yield strengths sufficient for many applications, there is a continual need to prepare cast moldings having increased yield strengths. There is a further need to reduce the mass of vehicle components for improved fuel efficiency without sacrificing requisite yield strengths.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

In various aspects, the present disclosure provides a method of forming a lightweight, high-strength cast structural component comprising casting an aluminum-based alloy. The aluminum-based alloy has a composition comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum. The lightweight, high-strength cast structural component may have a yield strength of greater than or equal to about 270 to less than or equal to about 300 MPa. The lightweight, high-strength cast structural component may have an elongation of greater than or equal to about 7%, and, more preferably, greater than or equal to about 9%. The casting may be produced by low-pressure die casting or gravity casting processes. The lightweight, high-strength cast structural component may be heat treated after casting. In certain aspects, the heat treatment can be a T6 heat treatment, where the cast structural component is immersed in a solution followed by quenching, followed by artificial aging. When low-pressure die casting is contemplated, the presence of magnesium may be further limited to from greater than or equal to about 0.1 to less than or equal to about 0.6 wt. % and the presence of strontium may be further limited to from greater than or equal to about 0.001 to less than or equal to about 0.015 wt. %. When gravity casting is contemplated, the presence of magnesium may be further limited to from greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; the phosphorus may be further limited to an amount of less than or equal to about 0.001 wt. %; and the presence of strontium may be further limited to an amount of less than or equal to about 0.005 wt. %.

In yet other aspects, the present disclosure provides a method of forming a lightweight, high-strength cast structural component comprising casting an aluminum-based alloy by gravity casting. The aluminum-based alloy has a composition comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; strontium at less than or equal to about 0.015 wt. %; phosphorus at less than or equal to about 0.003 wt. %; and a balance of aluminum. The lightweight, high-strength cast structural component further may have a yield strength of greater than or equal to about 270 to less than or equal to about 300 MPa. The casting may be low-pressure die casting or gravity casting. The lightweight, high-strength cast structural component may be heat treated after casting. In certain aspects, the heat treatment can be a T6 heat treatment, where the cast structural component is immersed in a solution followed by quenching, followed by artificial aging. The cast structural component may have an elongation of greater than or equal to about 7%. The presence of magnesium may be further limited to from greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; the phosphorus may be further limited to an amount of less than or equal to about 0.001 wt. %; and the presence of strontium may be further limited to an amount of less than or equal to about 0.005 wt. %.

In yet other aspects, the present disclosure provides a method of forming a lightweight, high-strength cast structural component comprising an aluminum-based alloy is formed from a casting by low-pressure die casting. The alloy material has a composition comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum. The lightweight, high-strength cast structural component further may have a yield strength of greater than or equal to about 270 to less than or equal to about 300 MPa. The lightweight, high-strength cast structural component may have an elongation of greater than or equal to about 7%, and, more preferably, greater than or equal to about 9%. The lightweight, high-strength cast structural component may be heat treated after casting. In certain variations, the heat treatment can be a T6 heat treatment where the cast structural component is immersed in a solution followed by quenching, followed by artificial aging. The presence of magnesium may be further limited to greater than or equal to about 0.1 to less than or equal to about 0.6 wt. % and the presence of strontium may be further limited to greater than or equal to about 0.001 to less than or equal to about 0.015 wt. %.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 shows a representative wheel manufactured according to an aspect of this invention.

FIG. 2 shows a flowchart of an exemplary process for preparing a lightweight, high-strength cast structural component according to an embodiment of the present disclosure.

FIG. 3 shows a flowchart of an exemplary process for preparing a lightweight, high-strength cast structural component according to an alternative embodiment of the present disclosure.

Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

DETAILED DESCRIPTION

The following description of the various aspects of the present disclosure is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific compositions, components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed, unless otherwise indicated.

Although the terms first, second, third, etc. may be used herein to describe various steps, elements, components, regions, layers and/or sections, these steps, elements, components, regions, layers and/or sections should not be limited by these terms, unless otherwise indicated. These terms may be only used to distinguish one step, element, component, region, layer or section from another step, element, component, region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first step, element, component, region, layer or section discussed below could be termed a second step, element, component, region, layer or section without departing from the teachings of the example embodiments.

Spatially or temporally relative terms, such as “before,” “after,” “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially or temporally relative terms may be intended to encompass different orientations of the device or system in use or operation in addition to the orientation depicted in the figures.

It should be understood for any recitation of a method, composition, device, or system that “comprises” certain steps, ingredients, or features, that in certain alternative variations, it is also contemplated that such a method, composition, device, or system may also “consist essentially of” the enumerated steps, ingredients, or features, so that any other steps, ingredients, or features that would materially alter the basic and novel characteristics of the invention are excluded therefrom.

Throughout this disclosure, the numerical values represent approximate measures or limits to ranges to encompass minor deviations from the given values and embodiments having about the value mentioned as well as those having exactly the value mentioned. Other than in the working examples provided at the end of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. If, for some reason, the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein may indicate a possible variation of up to 5% of the indicated value or 5% variance from usual methods of measurement.

In addition, disclosure of ranges includes disclosure of all values and further divided ranges within the entire range, including endpoints and sub-ranges given for the ranges.

In various aspects, the present disclosure provides methods of casting a strong, lightweight aluminum-based alloy. By “aluminum-based” it is meant that the composition is primarily comprised of aluminum, generally greater than or equal to about 90 wt. % aluminum. As used herein, the term “composition” refers broadly to a substance containing at least the preferred metal elements or compounds, but which may also comprise additional substances or compounds, including additives and impurities. The term “material” also broadly refers to matter containing the preferred compounds or composition. The present disclosure further relates to methods of making preferred embodiments of the aluminum-based alloy, as well as to methods of making components with preferred embodiments of the inventive alloy.

“Low-pressure die casting” as used herein is a type of metal casting process where typically a metal melt is in a sealed furnace having a riser tube at a pressure of less than or equal to about 0.7 bar (at least in certain variations). A die may be connected to the riser tube and positioned above the sealed furnace having the metal melt. Optionally, a degasser is introduced to reduce gasses present in the metal melt. A pressurized gas is introduced into the sealed furnace, which forces the metal melt through the riser tube and into the die. The pressurized gas is kept for a duration sufficient to fill the die with the metal melt and to allow the metal melt in the die to solidify. Once the casting solidifies, the pressurized gas is released, the metal melt in the riser tube returns to the sealed furnace, and the die opens to release the casting. The process may then be repeated after closing the die.

“Gravity casting” as used herein is a type of metal casting process where a metal melt is introduced into a die by a pouring cup or a ladle or the like. Optionally, a degasser is introduced to reduce gasses present in the metal melt. After solidification, the die is opened and the casting removed.

“T6 heat treatment” as used herein is a two-step heat treatment process involving a solution treatment with hot-water quenching, followed by an artifical aging treatment. By way of example, the first step generally involves providing a solution treatment by heating a casting to from greater than or equal to about 535° C. to less than or equal to about 545° C. for a period of less than or equal to about eight hours, followed by hot water quenching at from greater than or equal to about 70° C. to less than or equal to about 90° C. The second step generally involves an artificial aging treatment, wherein the casting is subject to a temperature of from greater than or equal to about 4 to less than or equal to about 20 hours.

The present disclosure provides methods of forming a lightweight, high-strength cast structural component. High-strength, lightweight alloy components are particularly suitable for use in components of an automobile or other vehicle (e.g., motorcycles, boats), but may also be used in a variety of other industries and applications, including aerospace components, industrial equipment and machinery, farm equipment, heavy machinery, by way of non-limiting example. While not limiting, the present methods and materials are particularly suitable for forming lightweight, high-strength components for a vehicle, including chassis and powertrain castings, such as wheels, lightweight valves, lightweight pistons, knuckles, control arms, and engine blocks, and additional powertrain components such as oil pans and engine heads, by way of non-limiting example.

Referring first to FIG. 1, an exemplary automotive structural component, such as wheel 10, is shown that can be produced from the casting methods disclosed herein. In certain variations, a lightweight, high-strength cast structural component according to the present disclosure may be cast by low-pressure die casting or gravity casting. After casting, the lightweight, high-strength cast structural component is further subjected to a heat treatment process and more preferably to a T6 heat treatment process. The lightweight, high-strength cast structural component may be formed of an aluminum-based alloy material having a composition comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum. In certain embodiments, the magnesium is present in an amount of greater than or equal to about 0.1 to less than or equal to about 0.6 wt. % and the strontium is present in an amount of greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %. In yet other embodiments, the magnesium is present in an amount of from greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; the phosphorus is present in an amount of less than or equal to about 0.001 wt. %; and the strontium is present in an amount of less than or equal to about 0.005 wt. %.

In yet other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting essentially of silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum. In still other embodiments, the lightweight, high-strength cast structural component is preferably formed of an aluminum-based alloy material having a composition consisting of silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum. In yet other embodiments, the lightweight, high-strength cast structural component is preferably formed of an aluminum-based alloy material having a composition consisting essentially of silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.6 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %; and a balance of aluminum. In still other embodiments, the lightweight, high-strength cast structural component is preferably formed of an aluminum-based alloy material having a composition consisting of silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.6 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %; and a balance of aluminum.

In yet other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting essentially of silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.001 wt. %; strontium at less than or equal to about 0.005 wt. %; and a balance of aluminum. In still other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting of silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.001 wt. %; strontium at less than or equal to about 0.005 wt. %; and a balance of aluminum.

In yet other embodiments, the lightweight, high-strength cast structural component may be formed of an aluminum-based alloy material having a composition comprising silicon at greater than or equal to about 4.5 to less than or equal to about 5.5 wt. %; iron at less than or equal to about 0.15 wt. %; chromium at greater than or equal to about 0.25 to less than or equal to about 0.35 wt. %; magnesium at less than or equal to about 0.5 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.1 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum. In certain embodiments, the magnesium is present in an amount of greater than or equal to about 0.1 to less than or equal to about 0.5 wt. % and the strontium is present in an amount of greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %. In yet other embodiments, the magnesium is present in an amount of from greater than or equal to about 0.1 to less than or equal to about 0.3 wt. %; the phosphorus is present in an amount of less than or equal to about 0.001 wt. %; and the strontium is present in an amount of less than or equal to about 0.005 wt. %. In yet other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting essentially of silicon at greater than or equal to about 4.5 to less than or equal to about 5.5 wt. %; iron at less than or equal to about 0.15 wt. %; chromium at greater than or equal to about 0.25 to less than or equal to about 0.35 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.1 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %; and a balance of aluminum. In still other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting of silicon at greater than or equal to about 4.5 to less than or equal to about 5.5 wt. %; iron at less than or equal to about 0.15 wt. %; chromium at greater than or equal to about 0.25 to less than or equal to about 0.35 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.1 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %; and a balance of aluminum. In still other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting essentially of silicon at greater than or equal to about 4.5 to less than or equal to about 5.5 wt. %; iron at less than or equal to about 0.15 wt. %; chromium at greater than or equal to about 0.25 to less than or equal to about 0.35 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.3 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.1 wt. %; phosphorus at less than or equal to about 0.001 wt. %; strontium at less than or equal to about 0.005 wt. %; and a balance of aluminum. In still other embodiments, the lightweight, high-strength cast structural component is formed of an aluminum-based alloy material having a composition consisting of silicon at greater than or equal to about 4.5 to less than or equal to about 5.5 wt. %; iron at less than or equal to about 0.15 wt. %; chromium at greater than or equal to about 0.25 to less than or equal to about 0.35 wt. %; magnesium at greater than or equal to about 0.1 to less than or equal to about 0.3 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.1 wt. %; phosphorus at less than or equal to about 0.001 wt. %; strontium at less than or equal to about 0.005 wt. %; and a balance of aluminum.

In certain aspects, the lightweight, high-strength cast structural component formed of such an aluminum alloy exhibits a yield strength of greater than or equal to about 270 to less than or equal to about 300 MPa. The lightweight, high-strength cast structural component may exhibit an elongation of greater than or equal to about 7% and more preferably greater than or equal to about 9%.

As mentioned above, the cast structural component is lightweight. More specifically, the aluminum-based alloy material having compositions according to the present disclosure is on average about 5 to about 10% lighter than a similar structural component cast of a conventional aluminum alloy, such as A356. One exemplary, non-limiting composition of A356 includes copper at less than or equal to about 0.05 wt. %; silicon at from greater than or equal to about 6.5 to less than or equal to about 7.5 wt. %; magnesium at from greater than or equal to about 0.3 to less than or equal to about 0.45 wt. %; manganese at less than or equal to about 0.05 wt. %; titanium at from greater than or equal to about 0.04 to less than or equal to about 0.15 wt. %; zinc at less than or equal to about 0.05 wt. %; iron at less than or equal to about 0.09 wt. %; manganese at less than or equal to about 0.05 wt. %; beryllium at less than or equal to about 0.0008 wt. %; trace elements at less than or equal to about 0.15 wt. %; and a balance of aluminum. As will be appreciated by those of skill in the art, such a composition of A356 is representative, but the composition of A356 may vary somewhat from the representative values disclosed here depending on variation in the standard used and other manufacturing parameters. Moreover, as noted above, many metal parts can be made using the compositions according to the present disclosure to form vehicle components. Vehicles having metal parts made using the compositions according to the present disclosure therefore potentially translate to weight savings. Reducing the weight of components in part is important for improving efficiency and is of great importance for fuel efficiency in mobile applications, such as in automobiles.

As mentioned above, the cast structural component is high strength. More specifically, the aluminum-based alloy materials having compositions according to the present disclosure exhibit a yield strength of greater than or equal to about 270 to less than or equal to about 300 MPa. A conventional aluminum alloy, A356, on the other hand, exhibits a yield strength of only about 150-180 MPa. While not limiting the present disclosure to any particular theory, the addition of chromium to the aluminum alloy is believed to provide higher strength by providing nano-scale precipitation after T6 heat treatment.

The other elements incorporated in the aluminum-based alloy also offer certain benefits to the component as a whole. More specifically, by way of limiting example, limiting the amount of iron is believed to prevent the formation of intermetallic phases, which would otherwise dramatically reduce ductility. Further, the presence of silicon is believed to provide good castability for thick wall castings. The presence of magnesium is believed to provide resistance to anti-cold cracking. The presence of titanium is believed to further improve the ductility of the casting and reduce the risk of hot cracking. Finally, the presence of strontium is believed to provide eutectic phase morphology control.

The low-pressure die casting processes preferable for use with the compositions according to the present disclosure shall now be further described. As described above generally, low-pressure die casting is a process where a metal melt is in a sealed furnace having a riser tube. A pressurized gas is added to the sealed furnace, which forces the metal melt through the riser tube and into a die. According to the present disclosure, the casting temperature is controlled at a temperature of greater than or equal to about 715° C. to less than or equal to about 730° C. to ensure the aluminum-based alloy is kept in a liquidus state. Controlling the temperature close to a temperature sufficient to liquidize the aluminum-based alloy is desired to reduce the amount of degassing necessary. Prior to casting, the aluminum-based alloy melt undergoes a degassing process sufficient to limit hydrogen in an amount of from greater than or equal to about 0.1 to less than or equal to about 0.15 cc per 100 g of the aluminum-based alloy melt. The degassing may be accomplished by ways known in the art, such as by introducing purging gas bubbles. At least a portion of the aluminum-based alloy melt is introduced into the die and allowed to solidify. Once the casting solidifies, the pressurized gas is released, the remaining aluminum-based alloy melt in the riser tube returns to the sealed furnace, and the die opens to release the casting. The process may be completed once the die is again closed.

The gravity casting process preferable for use in certain aspects with the compositions according to the present disclosure shall now be further described. As described above generally, gravity casting is a process where a metal melt is introduced into a die by a pouring cup or a ladle or the like. According to the present disclosure, the casting temperature is again controlled at a temperature of from greater than or equal to about 715° C. to less than or equal to about 730° C. to ensure the aluminum-based alloy is kept in a liquidus state. Controlling the temperature close to a temperature sufficient to liquidize the aluminum-based alloy is desired to reduce the amount of degassing necessary. Prior to casting, the aluminum-based alloy melt undergoes a degassing process sufficient to limit hydrogen in an amount of about 0.15 cc per 100 g of the aluminum-based alloy melt. The degassing may be accomplished by ways known in the art, such as by using a rotary impeller degasser in the ladle. Once the casting solidifies, the die is opened and the casting is removed.

The T6 heat treatment process preferable for use with the compositions according to the present disclosure shall now be further described. First, a solution heat treatment is provided by heating the casting to from greater than or equal to about 535° C. to less than or equal to about 545° C. for a period of greater than or equal to about eight hours. After providing the solution heat treatment, hot water quenching at from greater than or equal to about 70° C. to less than or equal to about 90° C. is then provided to the casting to rapidly cool the casting to prevent precipitation. Once the casting is cooled, an artificial aging treatment is provided at from greater than or equal to about 150° C. to less than or equal to about 175° C. from greater than or equal to about 4 to less than or equal to about 20 hours.

Referring to FIG. 2, a flowchart showing the steps of preparing a lightweight, high-strength cast structural component according to a low-pressure die cast method 200 is shown. A preferable aluminum-based alloy comprises silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum.

The aluminum-based alloy is melted (e.g., heated to above its melting point) to provide an aluminum-based alloy melt at 210. The aluminum-based alloy melt undergoes low-pressure die casting at 220 to create a lightweight, high-strength cast structural component. More specifically, the aluminum-based alloy melt is introduced into a sealed furnace kept at a temperature of from greater than or equal to about 715° C. to less than or equal to about 730° C. Optionally, the aluminum-based alloy melt is degassed to limit hydrogen in an amount of from about 0.1 to about 0.15 cc per 100 g of the aluminum-based alloy melt. The sealed furnace is connected to a riser tube, and the riser tube is connected to a die. A pressurized gas is introduced into the sealed furnace, which forces the aluminum-based alloy melt through the riser tube and into the die. At least a portion of the aluminum-based alloy melt is introduced into and fills the die and allowed to solidify. Once the casting solidifies, the pressurized gas is released, the remaining aluminum-based alloy melt in the riser tube returns to the sealed furnace, and the die opens to release the casting.

The casting is further subjected to T6 heat treatment at 230 to provide a lightweight, high-strength cast structural component according to the present disclosure. More specifically, the casting is subject to a solution heat treatment wherein the casting is heated to from greater than or equal to about 535° C. to less than or equal to about 545° C. for a period of less than or equal to about eight hours. After providing the solution heat treatment, hot water quenching at from greater than or equal to about 70° C. to less than or equal to about 90° C. is then provided to the casting to rapidly cool the casting. After cooling, the casting undergoes an artificial aging treatment at from greater than or equal to about 150° C. to less than or equal to about 175° C. for greater than or equal to about 4 to less than or equal to about 20 hours to provide the a lightweight, high-strength cast structural component according to the present disclosure. The lightweight, high-strength cast structural component according to the present disclosure exhibits a yield strength of greater than or equal to about 270 to less than or equal to about MPa, is greater than or equal to about 5 to less than or equal to about 10% lighter than a structural component cast of conventional comparative A356 aluminum alloy, and may have an elongation of greater than or equal to about 7% or even greater than or equal to about 9%.

Referring to FIG. 3, a flowchart showing the steps of preparing a cast structural component according to a gravity casting method 300 is shown. A preferable aluminum-based alloy comprises silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum.

The aluminum-based alloy melt is melted (e.g., heated to above its melting point) to provide an aluminum-based alloy melt at 310. The aluminum-based alloy melt undergoes gravity casting at 320 to provide a casting. More specifically, the aluminum-based alloy melt is introduced into a die by a pouring cup or a ladle or the like at the liquidus temperature of from greater than or equal to about 715° C. to less than or equal to about 730° C. Optionally, the aluminum-based alloy melt is degassed to limit hydrogen in an amount of about 0.15 cc per 100 g of the aluminum-based alloy melt. Once the casting solidifies, the die is opened and the casting is removed.

The casting is further subject to T6 heat treatment at 330 to provide a lightweight, high-strength cast structural component according to the present disclosure. More specifically, the casting is subject to a solution heat treatment wherein the casting is heated to from greater than or equal to about 535° C. to less than or equal to about 545° C. for a period of less than or equal to about eight hours. After providing the solution heat treatment, hot water quenching at from greater than or equal to about 70° C. to less than or equal to about 90° C. is then provided to the casting to rapidly cool the casting. After cooling, the casting undergoes an artificial aging treatment at from greater than or equal to about 150° C. to less than or equal to about 175° C. for greater than or equal to about 4 to less than or equal to about 20 hours to provide the a lightweight, high-strength cast structural component according to the present disclosure. The lightweight, high-strength cast structural component according to the present disclosure exhibits a yield strength of greater than or equal to about 270 to less than or equal to about 300 MPa, is greater than or equal to about 5 to less than or equal to about 10% lighter than a structural component cast of a conventional A356 alloy, and may have an elongation of greater than or equal to about 7%.

The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways.

Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

1. A method of forming a lightweight, high-strength cast structural component comprising:

casting an aluminum-based alloy comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum to form the lightweight, high-strength cast structural component.

2. The method of claim 1, wherein the lightweight, high-strength cast structural component has a yield strength of greater than or equal to about 270 MPa.

3. The method of claim 1, wherein the lightweight, high-strength cast structural component has an elongation of greater than or equal to about 7%.

4. The method of claim 1, wherein the lightweight, high-strength cast structural component has an elongation of greater than or equal to about 9%.

5. The method of claim 1, wherein the casting is a low-pressure die casting process.

6. The method of claim 1, wherein the casting is a gravity casting process.

7. The method of claim 5, further comprising T6 heat treating the lightweight, high-strength cast structural component after the casting.

8. The method of claim 5, wherein the magnesium is present in an amount of greater than or equal to about 0.1 to less than or equal to about 0.6 wt. % and the strontium is present in an amount of greater than or equal to about 0.01 to less than or equal to about 0.015 wt. %.

9. The method of claim 6, wherein the magnesium is present in an amount of greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; the phosphorus is present at less than or equal to about 0.001 wt. %; and the strontium is present in an amount of less than or equal to about 0.005 wt. %.

10. A method of forming a lightweight, high-strength cast structural component comprising:

gravity casting an aluminum-based alloy comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.5 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum.

11. The method of claim 10, wherein the lightweight, high-strength cast structural component has a yield strength of greater than or equal to about 270 MPa.

12. The method of claim 10, wherein the lightweight, high-strength cast structural component has an elongation of greater than or equal to about 7%.

13. The method of claim 10, further comprising T6 heat treating the lightweight, high-strength cast structural component after the casting.

14. The method of claim 10, wherein the magnesium is present in an amount of greater than or equal to about 0.1 to less than or equal to about 0.5 wt. %; the strontium is present in an amount of less than or equal to about 0.005 wt. %; and the phosphorus is present in an amount of less than or equal to about 0.001 wt. %.

15. A method of forming a lightweight, high-strength cast structural component comprising:

low-pressure die casting an aluminum-based alloy comprising silicon at greater than or equal to about 4 to less than or equal to about 7 wt. %; iron at less than or equal to about 0.15 wt. %; manganese at less than or equal to about 0.5 wt. %; chromium at greater than or equal to about 0.15 to less than or equal to about 0.35 wt. %; magnesium at less than or equal to about 0.8 wt. %; zinc at less than or equal to about 0.01 wt. %; titanium at greater than or equal to about 0.05 to less than or equal to about 0.15 wt. %; phosphorus at less than or equal to about 0.003 wt. %; strontium at less than or equal to about 0.015 wt. %; and a balance of aluminum to form the lightweight, high-strength cast structural component.

16. The method of claim 15, wherein the lightweight, high-strength cast structural component has a yield strength of greater than or equal to about 270 MPa.

17. The method of claim 15, wherein the lightweight, high-strength cast structural component has an elongation of greater than or equal to about 7%.

18. The method of claim 15, wherein the lightweight, high-strength cast structural component has an elongation of greater than or equal to about 9%.

19. The method of claim 15, further comprising T6 heat treating the lightweight, high-strength cast structural component after the casting.

20. The method of claim 15, wherein the magnesium is present in an amount of greater than or equal to about 0.1 to less than or equal to about 0.6 wt. and the strontium is present in an amount of greater than or equal to about 0. 01 to less than or equal to about 0.015 wt. %.