Hot deformation behavior and processing map of Al–Si–Mg alloys containing different amount of silicon based on Gleebe-3500 hot compression simulation

Abstract

The hot deformation behaviors of three aluminum alloys containing different silicon contents (S1: Al–0.6wt.% Si–0.5wt.% Mg; S2: Al–7.0wt.% Si–0.5wt.% Mg; S3: Al–12.3wt.% Si–0.5wt.% Mg) were studied by hot compressive tests using a Gleebe-3500 thermal simulator. The compression tests were carried out in a temperature range of 573–773K with strain rates of 0.01, 0.1, 1 and 5s−1, and the true strain up to 0.6. The new developed constitutive equation incorporating the effect of strain on material constants has been constructed, and a five-order polynomial has been ascertained. High correlation coefficient suggests that it can be used to accurately predict the flow stress during hot deformation of Al–Si–Mg alloys with different Si contents. Due to impeding dislocation motion by a great amount of silicon particles, both S2 and S3 alloys have much higher state steady flow stress σ and deformation activation energy Q than S1 alloy. The differences in σ and Q between S2 and S3 alloys are thought to be due to the difference of recrystallization maturity during hot deformation. Based on the constructed processing maps, the instability domain area of S2 alloy with 7wt.% Si is the largest among the studied alloys at the same strain. Due to much larger mushy zone of S2 alloy during solidification, the pore defects are prone to form in it that induces instability during hot deformation. It is also found that the strain has no considerable influence on the peak power dissipation efficiency during hot compression, but the effect of silicon content on it is not ignorable. In S2 and S3 alloys with high Si content, the peak power dissipation efficiency is less than that in S1 alloy, meaning that S2 and S3 alloys are more difficult to hot deformation than S1 alloy.