坯料预处理对挤压AZ91D管件组织和力学性能的影响

Effect of ingots pre-treatment on microstructure and mechanical properties of extruded AZ91D tube

研究了挤压比为6时镁合金AZ91D坯料前期分别经过预挤,固溶时效,预挤+固溶时效,预挤+固溶时效+固溶之后对挤压管件组织和力学性能的影响。结果表明:预挤使AZ91D坯料得到细化的等轴晶粒,使挤压出的管件的屈服强度提高15.72%,伸长率提高170%;坯料经固溶时效处理后,β-Mg17Al12从-αMg固溶体中成断续状析出,挤压后管件的抗拉强度略有降低;坯料经预挤+固溶时效+固溶之后挤压管件,晶粒明显细化,且经二次固溶,析出相均匀弥散分布于基体中,固溶强化作用较第一次固溶时明显,抗拉强度提高7.5%,坯料的二次固溶和预挤的综合作用使得挤压管件的伸长率提高345%。

The effect of ingots pre-treatment on microstructure and mechanical properties of extruded AZ91D magnesium alloy tube was studied.The results show that finer and equiaxed grains of the ingot are obtained and some cast defects in ingot are eliminated after pre-extrusion,which enhanced the yield strength by 15.72% and elongation by 170% for the extruded tube,respectively.After solution and aging treatment,β-Mg_(17)Al_(12) well-distributed precipitates from α-Mg solid solution and the grain size becomes a little coarser in the ingot,which causes the decrease of tensile strength of extruded tube by 14MPa.In the extruded tube,whose ingot was pre-extrusion+ solution aging+ solution treated,the grains are greatly refined and the second phase achieved an even and disperse distribution in the matrix because of twice solution,which has greater solution strengthening effect than first solution and tensile strength enhanced by 7.5%.Meantime,combination of twice solution and pre-extrusion on the ingot remarkably increases the elongation of extruded tube by 345% as well.