热处理对挤压AZ80镁合金杯形件组织和性能的影响

Effect of heat treatment on microstructure and properties of extruded AZ80 magnesium alloy cup shell

采用环形通道转角挤压工艺在350℃下制备AZ80镁合金杯形构件,并通过OM、SEM、拉伸试验等手段研究固溶、时效工艺对构件显微组织和力学性能的影响,确定与该新型挤压工艺相匹配的最佳热处理工艺参数。结果表明:成形过程中材料受强剪切应力作用,晶粒细化明显,杯形件壁部强度明显提升;残留共晶相引起应力集中导致伸长率降低;固溶处理有效促进脆性共晶相回溶,提升合金的伸长率;直接时效处理时,在共晶相周围聚集形成β-Mg17Al12析出带,降低合金的协调变形能力,导致时效强化效果不明显;通过固溶+时效处理,晶粒尺寸均匀,β-Mg17Al12相沿晶界均匀析出,合金的强度和塑性均得到明显提高。环形通道转角挤压成形的AZ80镁合金杯形件最佳热处理工艺参数为415℃×1.5 h固溶+175℃×36 h时效。

The AZ80 magnesium alloy cup shell was extruded via the annular channel angle extrusion at 350 ℃. The effects of solid solution and aging on the microstructure and mechanical properties of the components were studied by means of OM,SEM and tensile test. The optimum heat treatment parameters matching the new extrusion process were determined. The results show that during the forming process,the material is subjected to strong shear stress,the grain refinement is obvious,and the strength of the cup wall is obviously improved. The stress concentration caused by the residual eutectic phase leads to the decrease of the elongation. The solution treatment can effectively promote the re-dissolution of the brittle eutectic phase and increase the elongation of the alloy. During the process of direct aging treatment,the precipitation band of β-Mg17 Al12 formed around eutectic phase,which reduced the compatible deformation ability of the alloy and led to the aging strengthening effect.After solution and aging treatment,the grain size is uniform,and the phase of β-Mg17 Al12 precipitates uniformly along the grain boundary and the strength and plasticity of the alloy are obviously improved. The optimum heat treatment process parameters of the AZ80 magnesium alloy cup formed by the annular channel angular extrusion are:415 ℃×1.5 h solid solution +175 ℃×36 h aging.