Make Use Of Multiple Forgeing To Control The Microstructure And Mechanical Properties Of ZK60Alloy

Mg alloys with a structure have poor ductility and low strength. The products afterplastic processing often exhibit strong mechanical anisotropy, which greatly limits theapplications of Mg alloys. Multi-directional forging can generate a quite high plasticstrain and reduce mechanical anisotropy. It has becomes an effective method to tailormicrostructure and mechanical proterties of metals.In present paper, solution treated ZK60alloy was subjected to9passesmulti-directional forging (3%compression per pass and6%compression perpass)followed by aging treatment. The deformation twins generated during pre-straining areused to refine grains and the plastic deformation defects g contribute to nucleation ofprecipitate during aging. Mechanical properties and tension-compression yieldasymmetry of pre-strained material are sytematically studied. The influence ofpre-straining on microstructure and texture are discussed, too. Our results show that:(1) Many deformation twins and much dislocation are generated duringpre-straining. The twin lamella effectively subdivide the grains. The dislocations resultsin obvious work hardening. The recovery during aging treatment leads to a drop inaging hardness with time.(2) Both tension and compression strengths of pre-strained sample are much higherthan that of sample without pre-straining. A higher pre-strain level per-pass benefitshigher strengths along all three directions. The compression yield strength along Zdirection is the highest, while is the lowest along Y direction. The tension yield strengthalong X direction is the highest and is lowest along Z direction.(3) Pre-strainiing also induces preferred distribution of basal plane poles. Unliketranditional basal texture, the c-axies of grains are assigned along X direction, Ydirection and Z direction evenly. A preferred distribution of prismatic planes is alsoobserved. The texture of pre-strained samples also generates mechanical anisotropy. Aweak tension-compression yield asymmetry is observed along the three directions. Thetension-compression yield asymmetry along three directions is different from eachother.(4) The pre-straining greatly affects precipitation of alloys. A pre-strain promotes precipitation during aging treatment. A higher strain results in more particles and largeparticle size. The rod precipitates prefer to appear in grain and the bige plate-shapedprecipitates tend to nucleate at twin boundary.