Studying grain fragmentation in ECAE by simulating simple shear

A crystal plasticity based finite element model is developed to simulate grain fragmentation during equal-channel angular extrusion (ECAE). Route C multiple passes are approximated by repetitive planar simple shears. Results are presented in terms of plastic strain distribution, texture and grain size evolution. Numerical results are found to be in qualitative agreement with experimental observations associated with the grain refinement in ECAE.     

亚微米铜循环形变特征研究

本文研究了恒塑性应变控制下，egualchannelangularextrusion（ECAE）技术制备的亚微米铜的室温拉压时称循环形变行为，结果表明，亚微米钢在εpl＝5×10(－4)和1×10(－3)下表现出典型的循环软化特征、且直到断裂没有饱和阶段；而在εpl＝1×10(－4)下循环至5000周，应力幅仍没有明显变化，样品表面的光学显微镜及SEM－electronchannelingcontrast（SEM－ECC）技术研究发现：存在着宏观形貌与单晶表面滑移线相类似的‘滑移线’，‘滑移线’在侧面与载荷轴成45°，而在前表面与载荷轴相垂直：微观上‘滑移线’又可分为细而长的‘滑移线’和宽而短的微剪切带，根据晶界协同滑动和晶粒协同变形观点对上述两种形式的形变局部化的形成分别进行了分析     

Modeling compression reloads in copper pre‐strained by equal channel angular extrusion (ECAE)

When copper is deformed to large strains, as in Equal Channel Angular Extrusion (ECAE), its texture and microstructure change drastically and lead to plastic anisotropy upon reloading. In this work, we develop a multi‐scale model that accounts for both texture and subgrain microstructural evolution. Specifically the evolution of directional anisotropy in the single crystals is induced by the formation of planar dislocation walls. The model successfully predicts the flow responses of copper strained by a single pass of ECAE and subsequently compressed in each of three orthogonal directions.     

Numerical simulation of temperature field of AZ91D magnesium alloy during equal channel angular extrusion

The temperature field of AZ91D magnesium alloy extruded by equal channel angular extrusion (ECAE) has been simulated using finite element method (FEM). A series of tests were designed to obtain the simulation parameters: flow stress of AZ91D, friction factor and heat transfer coefficient. The simulated temperature agrees well with the measured one. The evolution of temperature and influencing factor was discussed in details. Furthermore, the extrusion pressure of ECAE was analyzed.     

基于DEFORM-3D的ECAE处理GCr15钢数值模拟

为了研究ECAE转角对GCr15钢晶粒细化的影响,借助于solidworks软件建立内角90°、120°两种转角模具模型,利用DEFORM-3D软件进行分析。结果表明:当内角Φ准为90°相对于Φ准为120°时,等效应变更大,也就是随着内角增加等效应变减小,这对晶粒细化是不利的;模具内角为90°时晶粒细化效果比内角为120°要好,塑性变形也大,但是要注意摩擦阻力的影响。     

The cold welding of copper to aluminum using equal channel angular extrusion (ECAE) process

In this research, it is shown that the production of bimetallic Al/Cu rod by cold ECAE process is feasible. The mechanism of the cold weld between the copper sheath and aluminum core is assessed using the characteristics of the mating surfaces both theoretically and by examining the SEM micrographs of the peeled surfaces. It is shown that the stretch produced by the shear strain in the process leads to the fracture of the work-hardened layer of the mating surfaces and then by extruding the virgin metal through the cavities of the cracks a cold weld is developed between the sheath and core of the rod. To achieve the cold weld, a threshold surface stretch of about 59% is required. It is shown that the decrease in die angle leads to a higher welding strength. Moreover, the presence of outer angle (ψ) impairs the quality of the weld.     

Effects of equal channel angular extrusion and aging treatment on R phase transformation behaviors and Ti3Ni4 precipitates of Ni-rich TiNi alloys

Ni-rich TiNi alloys were subjected to the effect of multiple equal channel angular extrusion (ECAE) treatments by B_C path at 500 °C. The characteristics of R phase transformation in aging treatment were dissimilar in the appearance and the temperature range to those counterparts induced by ECAE treatments. The fine lens-like shape Ti₃Ni₄ particles precipitated mainly in the regions of near grain boundaries and on the tangled grain boundaries after ECAE treatments. The effects and mechanisms of aging treatments and ECAE treatments on R phase transformation behaviors and Ti₃Ni₄ precipitates were investigated and discussed.