一种细化AZ31镁合金的固液两相区复合挤压工艺

为了通过细化晶粒提高镁合金综合力学性能,基于“工艺耦合,缩短流程”的想法,提出固液两相区挤压剪切复合成形工艺。以AZ31镁合金为研究对象,结合Anycasting技术,对固液两相区成形过程的浇铸过程及凝固过程进行模拟研究;结合实际实验选取合适的挤压参数,从而有效细化AZ31的组织并提高综合性能。结果表明:AZ31在变形区中因枝晶破碎和压力对过冷度的影响等促进了形核,在有效细化晶粒的基础上保证了尺寸的均匀性;且液相的存在有助于协调挤压过程中的变形,减少滑移和孪生变形对织构的影响,显著降低挤压织构的强度,180°角的基面宏观织构极值强度仅为5.3。剪切角能进一步细化晶粒,并提高综合力学性能;当剪切角度为150°时,综合力学性能最优,屈服强度为222 MPa,抗拉强度为309 MPa,伸长率为8%。

A fine microstructure of AZ31 magnesium alloy developed by composite extrusion in solid-liquid two-phase region

A novel semi-solid extrusion shear process was proposed based on the idea of"process coupling and shortening process",which can improve the comprehensive mechanical properties by grain refinement.The casting process and solidification process of AZ31 semi-solid forming process were simulated via Anycasting software.The appropriate extrusion parameters were selected by comparing the results of simulation and experiment.The results show that in the deformation zone,the nucleation of AZ31 is promoted by dendrite fragmentation and pressure,leading to the achievement of a fine and uniform structure.The presence of the liquid phase is beneficial to coordinating the deformation during extrusion,reducing the effect of slip and twining on the texture,and thus the extrusion texture is weakened.The maximum basal texture strength is only 5.3 when the shear angle is 180°.Shear angle can further refine grains and improve comprehensive mechanical properties.The best mechanical properties are obtained at the shear angle of 150° with yield strength of 222 MPa,tensile strength of 309 MPa and elongation of 8%.