中文摘要：

利用正挤压和往复挤压-正挤压联合工艺制备细晶Mg-6Zn-1Y合金，研究挤压工艺对合金组织的影响。结果表明：挤压比为11.3时，300、340℃正挤压合金品粒平均尺寸分别为2．7、12．9μm；300℃时再结晶机制为非连续动态再结晶机制，组织不均匀；340℃时为连续动态再结晶机理，组织均匀；挤压比6．1时，300℃挤压合金平均晶粒尺寸为3．2μm。降低挤压温度和增大挤压速率均可以提高组织细化程度。340℃往复挤压5道次后再经255℃正挤压合金组织均匀，平均晶粒尺寸为5.3μm，均匀的细晶组织归因于在往复挤压和正挤压过程中发生了2次动态再结晶。

英文摘要：

Mg-6Zn-lY alloy with very fine-grained was prepared by forward extrusion and combinational processes of reciprocating extrusion and forward extrusion. The influence of technological parameters on the microstructure of the alloy was studied. The results show that the average grain size of the alloy extrudes at 300 ℃ and 340 ℃ with extrusion ratio of 11.3 is 2.7 μm and 12.9 μm, respectively. The mean grain size of Mg-6Zn-IY alloy extruding at 300 ℃ with extrusion ratio of 6.1 is 3.2 μm. The grain size of as-extruded Mg-6Zn-IY alloy is smaller with the lower extrusion temperature or larger extrusion ratio. The refinement mechanism is non-continuous dynamic recrystallization extruded at 300 ℃. However, It is is continuous dynamic recrystallization extruded at relatively higher temperature, such as 340℃ . After 5 pass reciprocating extrusion at 340 ℃ and a forward extrusion at 255 ℃, the grain size is 5.3 μm. The uniform and fine equiaxed grains can be obtained that which can attribute to the dynamic recrystallization occuring two times during reciprocating extrusion and forward extrusion.