A356.2合金半固态坯料的复合制备工艺

Preparation of A356.2 Alloy Semi-solid Billets by Composite Technology

通过近液相线浇注、等径角挤压和半固态保温处理复合工艺制备了A356.2合金半固态坯料。利用金相显微镜和金相分析系统测量各工艺参数下制得半固态坯料的等积圆直径和形状系数,并对测量结果进行分析。结果表明,该复合工艺可以制备性能优良的A356.2合金半固态坯料,平均晶粒尺寸在57.4～87.2μm之间,形状系数在0.74～0.91之间;近液相线浇注可以获得呈蔷薇状和团状的晶粒细小坯料,等径角挤压使晶粒发生了明显的变形和破碎,累积了大的变形能,保温处理过程中晶粒逐步向近球状和球状转变,同时晶粒尺寸增大。

A356.2 alloy semi-solid billets were prepared by near liquidus pouring combining with equal channel angular extrusion and semi-solid isothermal treatment. Equivalent spherical diameter and shape factor of the semi-solid billets were measured by metallographic microscope and metallographic analysis system. The results reveal that A356.2 alloy semi-solid billets with desirable properties in which average grain size is in range of 60~90 μm and shape factor is in range of 0.7~0.9 can be successfully prepared by the composite technology. Semi-solid billets with fine rosette and lumpy grain can be obtained by near liquidus pouring,and grain accumulate severe energy of deformation through severely distortion and breaking during ECAE process,which results in the gradual transformation of grain into near-spherical and spherical structure with the increase of grain size.