Plastic Deformation Behaviors And Mechanical Properties Of Extrusion And Rolled ZK60 Magnesium Ally

As the lightest structural metal material, magnesium alloys have enormous potential for applications in the automotive, aerospace, automobile and medical industries. Among the magnesium alloys, ZK60 alloys have attracted more and more attention as their high strength and excellent high temperature superplastic.In recent years, researchers have made a lot of studies on ZK60 magnesium alloys. Severe plastic deformation techniques, like friction stir process, equal-channel angular processing and high pressure torsion have been utilized to produce ZK60 alloys. But, there are relatively few reports about transformation of deformation mechanisms at given temperature and ZK60 alloys prepared by conventional rolling method.In this study, we investigated the effect of temperature on deformation behavior of extruded ZK60 alloy and optimized a conventional rolling process for achieving superplastic ZK60 magnesium alloy sheets. On this basis, we explored a new type of industry, i.e., double hard-plate rolling. The main conclusions are as follows:(1) The extruded ZK60 alloys had excellent mechanical properties at room temperature, especially in TD direction(?0.2=147MPa, ?b=321MPa, δf=39%). Those excellent strength and plasticity properties were closely associated with fine grain(~4.5?m). With the rise of temperature, the plastic anisotropy gradually weakened(?D room=62%, ?D150℃=38%, ?D275℃=13%). Those changes had a good relationship with deformation mechanism, with the increase of temperature, deformation mechanism changed from slip, twinning and non-basal slip to grain boundary slide and rotation.(2) Developed a convenient rolling process and heat treatment for ZK60 alloy sheets. This plates had an average grain size ~3.5?m, and this grain smaller than the grain size of ZK60 alloys reported in other literatures. There yield strength, tensile strength and the elongation-to-failure were 239 MPa, 308 MP and 29% at room temperature, respectively.(3) It is found that the fine-grained ZK60 alloys has excellent superplastic, and it is elongation-to-failure reached 641% at 275℃ and at a strain rate of 1?10-3s-1. The main reason was that the fine grain structure(~3.5?m) was conducive to grain boundary sliding and rotation. At the same time, the dislocation creep controlled by grain boundary diffusion was considered the main accommodation mechanism.(4) Thickness reduction about 75% can be achieved by cold rolling just one pass for ZK60 magnesium alloys used by double hard-plate rolling process firstly. This plate had excellent mechanical properties(?0.2=208MPa, ?b=314MPa, δf=25%). This mechanical performance index compared favorably with ZK60 sheets produced by multi pass and small reduction rolling, but double hard-plate rolling process not only simple but economical environmental protection.