CRACK SUSCEPTIBILITY OF BINARY ALUMINUM ALLOYS: ANALYTICAL EQUATIONS

摘要

The crack susceptibility curves (crack susceptibility v.v. solute content C_0) of binary Al alloy systems were calculated by plotting the maximum | dT/d(fs)~(1/2) | vs. C_0, where T is temperature, fs fraction solid, and the maximum | dT/d(fs)~(1/2) | a crack susceptibility index proposed and verified recently. Two simple equations were derived based on binary phase diagrams with straight solidus and liquidus lines to calculate the location (C_0)_(peak) and height | dT/d(fs)~(1/2) |_(peak) of the peak of the crack susceptibility curve without having to calculate the curve first. The effect of the eutectic line, liquidus line and solidus line of a eutectic phase diagram on the crack susceptibility was demonstrated. Erst, | dT/d(fs)~(1/2) |_(peak) tends to decrease when the eutectic line is raised, the liquidus line steepened, or the solidus line made shallower. Second, back diffusion tends to increase (C_0)_(peak) and decrease | dT/d(fs)~(1/2) |_(peak). These tendencies agreed with the two equations and with the reported crack susceptibility of Al-Si and Al-Mg alloy systems.