Study on high strength casting Al-Si alloys (1st Report) (UDC 669・715'782-14) Effect of chromium on Al-Si alloys HISATSUNE Chuyo*・SHINODA Takeo** 1. Ternary diagram of Aluminium-Silicon-Chromium alloys. The diagram of Al-rich alloys containing silicon and chromium was investigated by means of thermal analysis, microscopic and X-ray examination. Al-rich corner up to 12% silicon and up to 4% chromium was studied. From several constitutional sections which have the same chromium-content

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... y, the following conclusions were drawn: (1) In the range studied, the primary crystals are (Al), θ, η, α, β and Si. (2) The ternary refined compounds α and β are found to exist. (3) The non variant points are: Liq.+Al11Cr7→←Al7Cr+α, at 647°, Liq.+Al7Cr→←(Al)+α, at 630°, Liq.+α→←(Al)+β, at 626° and Liq.→←(Al)+Si+β, at 576°. 2. Effect of chromium on mechanical properties of Al-Si alloys. By adding of 0.3% chromium to the Al-Si alloys (5 to 12%Si), the micro-structure of sand casting and the mechanical properties are improved.