Study On The Effects Of High Pressure On The Annealed Microstructure Of A Cold-rolled Aluminum-magnesium Alloy

Optical microscope(OM), X-Ray diffraction (XRD), microhardness test, transmissionelectron microscope (TEM), electron backscatter diffraction (EBSD) and other methodswere used to systematically study the effects of the high pressure(1GPa～6GPa) onannealed microstructure of the cold-rolled Al-Mg alloy (AA5182). Meanwhile, thethermodynamic stability of the second phases of Al-Mg alloy was calculated by the firstprinciples density based on functional theory. The results show that with increasingpressure (1GPa～to6GPa), the formation enthalpy of Mg2Si and Al6(Fe,Mn) increasesgradually but the thermal dynamic stability reduces accordingly. When annealed at370℃for30min at normal pressure, the phases of cold-rolled Al-Mg (AA5182) alloy arecomposed of α(Al)、β(Mg2Al3)、 Al6(Fe,Mn) and Mg2Si. Compared with the normalpressure annealing, high pressure annealing (1GPa～6GPa) inhibits the second phaseprecipitation and the higher the pressure is, the more obvious this phenomenon is, whichcan be explained by the results of first principle. After high pressure (at370℃for30min、4GPa and6GPa, respectively) annealing, the microstrain and dislocation density ofAl-Mg（AA5182）alloy (Cold rolling reduction of91.0%) are close to those of cold-rolledAl-Mg and increase with the pressure increasing. However, the mosaic block size reduceswith the pressure increasing. Cold-rolled Al-Mg (AA5182) alloy after normal pressureannealing (at370℃for30min) has completely recrystallized. However, at less than3GPa, when the reduction is less than55.7%, partial recrystallization occurs, and when thereduction is greater than55.7%, complete recrystallization occurs. When annealed at4GPa,5GPa and6GPa, recrystallization does not occur in all tested specimens withdifferent reduction. The analysis by XRD, EBSD and TEM show that pressure retards therecrystallization of cold-rolled Al-Mg (AA5182) alloy.