【作者】 李元东； 郝远； 阎峰云；

【Author】 LI Yuan-dong, HAO Yuan, YAN Feng-yun (College of Materials Science and Engineering, Gansu Univ. of Tech., Lanzhou 730050,China)

【机构】 甘肃工业大学材料科学与工程学院；

【摘要】 研究了应变诱发熔体激活法SIMA(Strain-Induced Melt Activation)对制备AZ91D镁合金半固态非枝晶组织的细化作用。实验结果表明:预变形处理破坏了铸态组织原有的枝晶形貌,减小了原始晶粒尺寸,同时也为试样内部晶粒在高温下的演变提供了驱动力。AZ91D合金经20%、30%预变形后,在半固态温度升温(540-580℃)或保温(570℃)过程中,其组织形貌由粗化的等轴晶及短树枝晶依次转变为小块状细晶粒→团块状→球状大晶粒。在等温热处理过程中,试样内部体系寻求能量最低状态也是组织转变的一个不可忽略的因素。变形量越大,570℃保温过程中组织的粗化的趋势越明显.预变形对AZ91D镁合金非枝晶组织的细化作用主要表现在570℃保温30min以前。与未预变形的合金制备的非枝晶组织相比较,经预变形处理的试样是较好的半固态成型材料。更多还原

【Abstract】 The role of Strain-Induced Melt Activation (SIMA) in grain refinement for producing semi-solid AZ91D alloy with non-dendrites is studied. The results indicate that the as-cast dendritic structure of AZ91D was destroyed in the compressive pre-deformation and the grain size is descended. The pre-deformation provided the power of driving for structural evolution at high temperature. After AZ91D alloy with dendrites experienced 20%、30% compressive deformation, its microstructure changes from coarse equiaxed grains with short dendrites, in turn, into small piece, big bump, big spherical grains which will grow up later during the isothermal heat-treatment at semi-solid temperature between 540℃ to 580℃. On the other hand, it is not neglect that system in the sample seeks for the lowest energy condition during the semi-solid isothermal heat-treatment. With increase of the deformation, the trend of grain coarsen become significant. The role of SIMA in grain refinement for producing semi-solid AZ91D alloy with non-dendrites is during the isothermal heat-treatment holding 0 min to 30 min at 570℃. The SIMA AZ91D alloy fits well the requirement for Semi-solid forming comparing with the original AZ91D alloy.更多还原