【摘要】 将铸态Mg92.5Zn6.4Y1.1镁合金往复挤压2,4,8,12不同道次,然后分别正挤压制成12mm的棒材。采用OM,XRD及DTA研究了往复挤压不同道次镁合金的组织和力学性能。研究表明,铸态Mg92.5Zn6.4Y1.1镁合金往复挤压后,组织得到显著细化,力学性能得到大幅度提高,获得了高强韧镁合金。2道次后,晶粒约5μm,拉伸强度超过300MPa,伸长率高达20%。继续增加往复挤压道次,晶粒细化和拉伸性能提高均不明显,当往复挤压12道次时,拉伸强度明显降低,而伸长率达到23%。Mg92.5Zn6.4Y1.1镁合金的伸长率大幅度提高归因于在往复挤压过程中,铸态组织中的缩松、缩孔等缺陷闭合和成分偏析非均匀相的分布均匀化,以及晶粒的破碎、回复和动态再结晶所引起的晶粒细化及材料的流动,最终获得完全致密、细小而均匀的等轴晶组织。更多还原

【Abstract】 As-cast Mg92.5Zn6.4Y1.1 magnesium alloys were prepared by reciprocating extrusion(RE) and forward extrusion processes.The as-cast alloys were firstly reciprocating extruded for 2,4,8 and 12 passes,and then further extruded into 12mm bar,respectively.Microstructures and mechanical properties were investigated with optical microscope(OM),transmission electronic microscope(TEM),X-ray diffraction(XRD) and differential thermal analysis(DTA).The results show that RE process can prepare sound and solid material.The grain size is approximately 5μm and UTS preponderate over 300MPa and elongation attain 20 percent after reciprocating extruded for 2 passes and a forward extrusion.The grain refine and tensile properties are not improving clearly with increasing RE passes,and the tensile properties decrease very clearly with 12 passes,but the elongation properties up to 23 percent.Reason of the further increase of the elongation after several RE passes is due to that the micro-pores,shrinkage-pores and the nonuniform phase of element microsegregation have completely eliminated to yield a fully dense,refined,more equiaxed and uniform microstructure,and grain refinement involve fragmentation,dynamic recovery and dynamic recrystallization,repeated mass flow during reciprocating extrusion and forward extrusion.更多还原