| 摘要 |
PROBLEM TO BE SOLVED: To provide an aluminum alloy piston exhibiting excellent fatigue strength even in a temperature region as high as 200 to 250 deg.C. SOLUTION: After forging, this aluminum alloy piston has a composition containing 11-13% Si, 0.2-1.2% Fe, 3.5-4.5% Cu, 0.2-0.5% Mn, 0.3-1.0% Mg, 0.01-0.2% Ti, 0.0002-0.02% B, 0.005-0.02%s P, and Ca in an amount controlled to <=0.005%. The aluminum alloy piston has a forged structure in which Si and an intermetallic compound both crystallized out at the time of casting are uniformly dispersed, in 5-35μm average grain size, in a matrix after forging and gas content is controlled to <=0.25 cc/100 g-Al. Further, the average number of inclusions is controlled to <=0.01 piece/cm2 by K10 value in a stage of an ingot, and forming is performed by forging.
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