Abstract: An aluminum alloy for casting, made of an Al—Si—Cu—Mg alloy which consists of specific amounts of Si, Cu, and Mg, in addition to specifically desired amounts of titanium, phosphorus, boron, and optional additional chemical elements sodium and strontium, with the balance of the aluminum alloy comprising aluminum and any impurities. When a content of phosphorus is defined as X mass %, the content of phosphorus, a content of Y mass % of sodium, and a content of Z mass % of strontium satisfy the following relationships: 0.45Y+0.24Z+0.003?X?0.45Y+0.24Z+0.01; 0?Y?0.01; and 0?Z?0.03. The aluminum alloy ensures surface smoothness of a cast article by specifying the phosphorus content. This minimizes a surface segregation layer, even in production of a cast article using a molten metal containing a eutectic structure modifier such as sodium.

Abstract: The present invention is an aluminum alloy for low-pressure casting, and the aluminum alloy is made of an Al—Si—Cu—Mg alloy and contains: 8.0 to 12.6 mass % of Si; 1.0 to 2.5 mass % of Cu; 0.3 to 0.8 mass % of Mg; and 0.2 mass % or less of Ti, wherein the aluminum alloy further contains X mass % of P, Y mass % of Na, and Z mass % of Sr, with the balance including Al and inevitable impurities, and wherein a content of P, a content of Na, and a content of Sr satisfy all of the following relationships: 0.45Y+0.24Z+0.003?X?0.45Y+0.24Z+0.01; 0?Y?0.01; and 0?Z?0.03. The present invention ensures surface smoothness of the casted article by specifying the P content. This minimizes a surface segregation layer even in production of a casted article using a molten metal containing a eutectic structure modifier such as Na.

Abstract: The present invention provides: a compressor impeller that cast from an aluminum alloy, has superior production characteristics, and exhibits stable high-temperature strength when used at temperatures around 200° C.; and a method for producing same. The compressor impeller that is cast from an Al alloy is provided with a boss section, a plurality of vane sections and a disc section; the boss section, the plurality of vane sections and the disc section excluding the end section comprise an Al alloy comprising a predetermined metal composition; and at the end section of the disc section, there are at least 10,000/mm2 of intermetallic compounds having a circle-equivalent diameter of 1-6 ?m, and there are no greater than 500/mm2 of intermetallic compounds having a circle-equivalent diameter exceeding 6 ?m.

Abstract: Provided is a forged material for a rotor for obtaining, by machining, a rotor including a hub portion and a plurality of blade portions. The forged material for a rotor comprises a hub forming section and a plurality of blade forming sections that one-to-one correspond to the plurality of blade portions. The plurality of blade portions each comprise a first end face that faces an outer peripheral surface of the hub portion and a second end face opposite from the first end face. The plurality of blade forming sections each comprise a blade-shaped surface having a shape that follows at least part of a contour of the second end face of the one-to-one corresponding blade portion.