Study on high strength casting Al -Si-Mg-Zn alloys (3rd report)

Abstract

The effects of the addition of Cr, Ti or Be on the mechanical properties at high temperatures(150°C, 250°C) and the casting-structural evaluation test of Al-5%Si-0.5%Mg-(0.72%)Zn alloys were investigated and the following results were obtained.The tensile strength of these alloys at test temperature 150°C were similar values, but at test temperature 250°C, the alloys containing Be always were superior to alloys without Be addition. These values of alloys containing Be were comparable to those of heat resisting Al alloys now used.Generally, in casting-structural evaluation test the mechanical properties of the alloys containing Be were superior to those alloys not containing Be. When alloys were cast in green sand mold with chill-plates, the bending test value of ZH alloy containing 0.3%Be was 660kg but the value of ZH alloy not containing Be was 620kg. The effects of Be addition was favourable. When alloys were cast in green sand mold with chill-plates, the notch tensile strength of ZH alloy containing 0.3%Be was 5052kg/mm2 and the strength of ZI alloy without Be addition was 41kg/mm2, and so the effect of Be addition was remarkable.It was reasonable that Al-5% Si-0.5 % Mg-2% Zn alloy was used as the basic alloy. About aging conditions after solution heat treatment at 550°C for 10hr, with respect to tensile strength and proof stress aging at 150°C for 20 hr is favourable, and with respect to elongation aging at 100°C for 50 hr is good.