Alpha plus beta type titanium alloy

Abstract

A (α+β) type Ti alloy contains 7 wt % to 8.5 wt % of Al, 0.5 wt % to 1.5 wt % of V, 1 wt % to 3 wt % of Mo, 1 wt % to 3 wt % Cr, 0.3 wt % to 1 wt % of Fe, 0.05 wt % to 0.1 wt % of rare earth element, Ti, and unavoidable impurities. The Ti alloy can be produced by varmelting, forging, rolling and casting pressure processing or powder metallurgy. The total amount of impurities of C, H, O, and N is not higher than 0.25 wt %. V, Mo, and rare earth elements are added in forms of Al—V intermediate alloy, Al—Mo intermediate alloy, and La—Ce mixed rare earth, respectively. The room-temperature tensile strength and yield strength of the Ti alloy are higher than those of Ti—6Al—4V by more than 30%, the high-temperature strength is superior to that of Ti—6Al—4V, density and cost are lower than those of Ti—6Al—4V.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a titanium (Ti) alloy, and more particularly to a high-strength cost-effective Alpha plus Beta (α+β) type Ti alloy.

2. Related Art

(α+β) type Ti alloys are widely applied in the fields such as aviation, aerospace, automobile, golf club head, and bicycle, in which Ti—6Al—4V alloy successfully developed by U.S.A. in 1954 is a typical representative. Ti—6Al—4V alloy has preferable comprehensive performance, and present usage of Ti—6Al—4V alloy has been over a half of all Ti alloys. However, the performance-to-price ratio of the Ti—6Al—4V alloy is not high enough, long-term working temperature is around 350° C., vanadium (V) of high content in the alloy makes the price of the alloy relatively high, and the room-temperature strength and high-temperature strength still have room to improve, which limit the further application of Ti—6Al—4V alloy in national defense and military industry and civilian products.

SUMMARY OF THE INVENTION

The present invention is directed to provide a high-strength (α+β) Ti alloy, which has a higher performance-to-price ratio than that of Ti—6Al—4V and a long-term working temperature up to 450° C.

The technical solution of the present invention is as follows.

A (α+β) type Ti alloy contains 7 wt % to 8.5 wt % of Al, 0.5 wt % to 1.5 wt % of V, 1 wt % to 3 wt % of Mo, 1 wt % to 3 wt % of Cr, 0.3 wt % to 1 wt % of Fe, 0.05 wt % to 0.1 wt % of rare-earth elements, and the rest are Ti and unavoidable impurities.

The Ti alloy of the present invention can be produced by general methods of preparing Ti alloy, such as varmelting, forging, rolling, and casting processing or powder metallurgy. The total amount of impurities of C, H, O, and N is controlled to be not higher than 0.25 wt %. V is added in form of Al—V intermediate alloy, and Mo is added in form of Al—Mo intermediate alloy, so as to ensure the accuracy and uniformity of the ingredients of the alloy, thereby ensuring the consistency of the performance of the alloy material. The rare earth elements are added in form of La—Ce mixed rare earth.

The Al content of the (α+β) type Ti alloy of the present invention is higher than that of Ti—6Al—4V, and the increase of the Al content has significant effect in improving the room-temperature strength and high-temperature strength, reducing the specific gravity, and increasing the elastic modulus. V, Mo, Cr, and Fe are β stabilizing elements. Compared with Ti—6Al—4V, the addition of V is significantly reduced, thus reducing the production cost of the Ti alloy. The addition of proper amount of rare-earth elements improves the antioxidant performance of the Ti alloy surface. The room-temperature tensile strength and yield strength of the (α+β) Ti alloy of the present invention is improved by more than 30% compared with Ti—6 Al—4V, high-temperature strength is significantly superior to Ti—6 Al—4V, density and cost are a little lower than those of Ti—6 Al—4V. Therefore, the Ti alloy of the present invention has higher performance-to-price ratio than that of Ti—6 Al—4V, and has broad market prospects.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

The Ti alloy of the present invention is manufactured by varmelting, forging, rolling and casting processing, the compositions of the alloy are formulated according to the alloy ingredients: 8.0 wt % of Al, 1.0 wt % of V, 2.0 wt % of Mo, 2.0 wt % of Cr, 0.5 wt % of Fe, 0.08 wt % of rare earth elements, and the rest of Ti and unavoidable impurities. An electrode composed of the alloy elements is melted in to an ingot by two times of vacuum consumable melting, and the melting vacuum is required to be lower than 1 Pa. During melting, V is added in form of Al—V intermediate alloy, Mo is added in form of Al—Mo intermediate alloy, rare earth elements are added in form of La—Ce mixed rare earth, and the amount of the elements C, H, O, and N is strictly controlled to be not higher than 0.25 wt %. The ingot is cogged and forged at 1000° C. to 1200° C., and then further forged at a low temperature of 900° C. to 1000° C., so as to get a plate block. Thereafter, the plate block is hot rolled at a temperature of 800° C. to 1000° C., and after annealing treatment, a hot rolled Ti alloy plate is obtained.

The resultant Ti alloy plate (3 mm thick) is tested by National iron of Steel Material Test Center, the room-temperature tensile strength is 1270 MPa, the yield strength is 1200 MPa, elongation after fracture is 10.0%, and the Rockwell hardness value is 42. The comprehensive performances at room temperature of the Ti alloy of the present invention and annealed Ti—6Al—4V alloy plate with the same thickness are compared, and the results are listed in Table 1.

TABLE 1
Comparison of room-temperature performances of Ti alloy
of the present invention and Ti—6Al—4V alloy
	Yield	Tensile	Rate of
	Strength	Strength	Elongation	Hardness	Density
Ti alloy Name	(MPa)	(MPa)	(wt %)	(HRC)	(g/cm3)
Ti—6Al—4V	870	925	≧10	36	4.5
Ti alloy of the	1200	1270	10	42	4.4
Present Invention

It can be seen from the data in the table that the density of the Ti alloy of the present invention is a little lower than that of Ti—6Al—4V, the room-temperature strength is much superior to that of Ti—6Al—4V, the tensile strength and yield strength are improved by more than 30% compared with Ti—6Al—4V, and the plasticity is similar to that of Ti—6Al—4V. The Al content of the Ti alloy of the present invention is higher than that of Ti—6Al—4V, but V content is much lower than that of Ti—6Al—4V, so the cost is lower than that of Ti—6Al—4V, and the performance-to-price ratio is significantly higher than that of Ti—6Al—4V. Further, as the tensile strength at 440° C. of the resultant Ti alloy plate of this embodiment is 960 MPa, and the tensile strength at 400° C. of Ti—6Al—4V is 645 MPa, the high-temperature strength of the Ti alloy of the present invention is significantly superior to that of Ti—6Al—4V.

Claims

1. An Alpha plus Beta (α+β) type titanium (Ti) alloy, comprising: 7 wt % to 8.5 wt % of Al, 0.5 wt % to 1.5 wt % of V, 1 wt % to 3 wt % of Mo, 1 wt % to 3 wt % of Cr, 0.3 wt % to 1 wt % of Fe, 0.05 wt % to 0.1 wt % of rare-earth elements, and the rest of Ti and unavoidable impurities.

2. The (α+β) type Ti alloy claimed as in claim 1, wherein total amount of impurities of C, H, O, and N is no higher than 0.25 wt %.

3. An Alpha plus Beta (α+β) type titanium (Ti) alloy, comprising: 8.0 wt % of Al, 1.0 wt % of V, 2.0 wt % of Mo, 2.0 wt % of Cr, 0.5 wt % of Fe, 0.08 wt % of rare-earth elements, and the rest of Ti and unavoidable impurities.

4. The (α+β) type Ti alloy claimed as in claim 3, wherein the total amount of impurities of C, H, O, and N is no higher than 0.25 wt %.