Research On Influence Of Solution And Aging Heat Treatment On Microstructure And Mechanical Properties Of As-Cast AZ80 Magnesium Alloy

With many advantages including low specific gravity,high specific strength,specific rigidity, damping process ability,excellent electromagnetic shielding and recyclability,magnesium alloys interest many researchers.The exploitation of magnesium alloys series with excellent properties is the mostly trend currently.But it is effective way that magnesium alloys in existence are appropriately technical processed.It is an effective way of enhancement of material's properties that material's microstructure is changed by heat treatment.So it's very important to investigate the effects of heat treatment on the microstructures and properties of AZ80 wrought magnesium alloy.The way is used in AZ80 wrought magnesium alloy in this paper in order to ameliorate material's microstructure and enhance its properties.Research on influence of solution and aging heat treatment on microstructure and mechanical properties of as-cast AZS0 magnesium alloy were systemically studied in this paper by OM,SEM,XRD,EDS,TEM as well as tensile,impact and hardness tests.The results indicated that:Theβ-Mg₁₇Al₁₂phase discontinuously distributed along the grain boundary was dissolved intoα-Mg matrix through the solution treatment.With higher temperature and longer time at solution treatment,the hardβ-Mg₁₇Al₁₂phase existed continuously at grain boundaries ofα-Mg phase vanishes,it precipitates atαphase dispersedly instead of precipitating at grain boundaries and the properties of the alloy are improved more distinctly.But the crystal grain was too big and the properties got worse if the temperature was too high or the time was too long,though the stretch rate increases continuously.Fractography demonstrates that as-cast alloy's tensile fracture is cleavage fracture and the alloy's tensile fracture mode changes from intergranular fracture to transgranular after solution treatment. The aging treatment after solution treatment madeβ-Mg₁₇Al₁₂phase occur with discontinuous and continuous precipitation from oversaturatedα-Mg solid solution.Three forms ofβ-Mg₁₇Al₁₂phase were found in this paper:â… Lath-shaped,â…¡Hexagonal-prismatic,â…¢Shot rod-shaped.The aging temperature had a great effect on the form ofβ-Mg₁₇Al₁₂phase. Lath-shapedβ-Mg₁₇Al₁₂phase precipitated continuously and quickly iu the alloy aged at high temperature(300℃).When the temperature rose,β-Mg₁₇Al₁₂phase precipitated discontinuously while the amount of continuousβ-Mg₁₇Al₁₂phase decreased.The lower the temperature,the huger the amount.The Hexagonal-prismatic and Shot rod-shapedβ-Mg₁₇Al₁₂phase appeared besides the Lath-shaped ones.Butβ-Mg₁₇Al₁₂phase needed a long time to nucleate and grow if the temperature was too low(140℃).The precipitated-discontinuousβ-Mg₁₇Al₁₂phase could evidently strengthen the alloy while the precipitated-continuous one couldn't.The yield strength of alloy were remarkably enhanced,but the elongation and impact toughness decreased seriously.The tensile fracture mechanism of alloy after aging treatment was brittle fracture of cleavage fracture.