纯钛粉末室温单道次等径角挤压变形行为

Deformation behavior of pure titanium powder extruded by single-pass equal channel angular pressing at room temperature

应用Deform-3D V6.1软件,对室温下纯钛的等径角挤压(ECAP)过程进行有限元模拟,研究试样的等效应变分布情况;并采用两通道夹角Ф=90°、外圆角Ψ=60°的模具,在室温下实现粉末烧结纯钛单道次ECAP变形,研究挤压后试样不同部位的显微组织和性能,以及等径角挤压对粉末烧结纯钛致密化的影响。模拟结果表明:变形主要集中在试样的中部,且最大等效应变出现在工件棱角处。实验结果表明,工业纯钛经单道次挤压变形后,变形主要发生在试样中部平行于挤压方向的纵截面;组织内存在大量的形变孪晶;晶粒碎化成板带状组织;显微硬度由1 450 MPa上升至2 244 MPa,提高约50%;粉末材料中的圆形孔隙被挤扁、焊合,因此,通过ECAP可使材料进一步致密化。

The equal channel angular pressing（ECAP） process of commercial pure titanium（CP-Ti） at room temperature was simulated by software Deform-3D V6.1.A single-pass ECAP at room temperature was successfully carried out in CP-Ti fabricated by powder metallurgy,using the die with a internal angle Ф of 90° and the outer curvature angle Ψ of 60°.The microstructures and properties of different parts of the sample after extrusion were studied,and the influence of ECAP on the densification of the CP-Ti was explored.Numerical simulation results show that deformation is mainly distributed in the central region of workpiece,and the maximum equivalent strain in the angular region of the channel.Experimental results show that single-pass ECAP deformation is mainly concentrated in the longitudinal section parallel to the extrusion direction in the central region.The equiaxed grains are broken into lath-like,and there are a large number of twins grains.The microhardness of the specimen increases from 1 450 MPa to 2 244 MPa.Round pores in the specimen are flat tended and welded.Therefore,the material density can be improved by ECAP deformation.