The Effects Of High Pressure On The Aging Behavior Of Aluminum-magnesium-Silicon Alloy

Al-Mg-Si alloys are widely used in building, transportation, industrial and aerospacemarkets due to their excellent plasticity and corrosion resistance, light weight and mediumstrength after appropriate working processes (such as rolling) and heat treatmentsincluding mainly solution, quenching and aging treatments. This article selected AA6061alloy as the research object. The aim of this study was to investigate the effects ofhigh-pressure on aging behaviors of AA6061alloy.In this paper, X-Ray diffraction (XRD), microhardness testing, transmission electronmicroscope (TEM) were used to systematically study the effects of the high pressure(1～5GPa) on aging microstructure and properties of the Al-Mg-Si alloy (AA6061).After aging at175℃for8h at different pressure, the main type of precipitateschanges apparently. With increasing pressure the size of precipitates in Al-Mg-Si alloy isgradually decreasing. After aging at3GPa for8h at different temperature, the size ofprecipitates is gradually decreased with aging temperature increasing. After aging at3GPa、275℃for different hours, the alloy structure changes significantly, with theincrease of aging time the size becomes larger. It also can be found the amount of Q phaseincreases with the aging time increasing. After cold-rolled Al-Mg-Si alloy (30%reduction)aging at175℃for8h at different pressure, it can be found that the amount of precipitatesof cold-rolled Al-Mg-Si alloy is more than the Al-Mg-Si alloy, and the size of precipitatesof cold-rolled Al-Mg-Si alloy is more uniform. It can be concluded that cold deformationis conducive to the precipitation of precipitates.Meanwhile, the thermodynamic stability of the second phases of Al-Mg-Si alloywas calculated by the first principles density based on functional theory. The results showthat with pressure increasing, the formation enthalpy of β″phase increases gradually, thethermal dynamic stability reduces. However, the formation enthalpy of GP zone, β′, β andQ phase is decreased with increasing pressure, which indicates its thermodynamic stabilitygradually increased.