纯钨等通道双转角挤压变形行为分析

Deformation Behavior of Pure Tungsten During Equal Channel Double Angular Pressing

作为一种新的大塑性变形(SPD)方法,基于等径角挤压(ECAP)开发了等通道双转角挤压(ECDAP)以减少冲头偏载。通过有限元模拟和实验研究分析了工业烧结纯钨在1道次ECDAP过程中的变形行为。结果表明:在相同工艺参数下,ECDAP模具的局部应力分布更加均匀,冲头的偏载得到了改善。经ECDAP产生的平均等效应变与ECAP类似,但是试样经过ECDAP变形发生二次剪切变形,应变分布的均匀性大大提高。此外,在二次剪切变形区晶粒尺寸减小到1.77μm,并且在转角区晶粒被明显拉长。由于霍尔-帕奇(Hall-Petch)强化和应变强化作用使得显微硬度得到提高。以上结果表明ECDAP工艺是生产超细晶金属材料的一种有效方法。

As a new severe plastic deformation(SPD)method,equal channel double angular pressing(ECDAP)is developed based on equal channel angular pressing(ECAP)to reduce the offset load.The deformation behavior of commercial sintered pure tungsten(W)during single pass ECDAP was analyzed quantitatively in this paper by finite element simulation and experiment investigation.The results show that,compared with ECAP,ECDAP exhibits more homogeneous local force of the die and improves the offset load of the punch with the same parameters.Meanwhile,the average effective strain introduced by ECDAP is similar to that of ECAP.Nevertheless,the uniformity of strain distribution is also greatly improved owing to the secondary shear deformation.In addition,grain size decreases to 1.77μm in the secondary shear deformation zone and the grains are elongated obviously in the angle zone.Hence,the microhardness is enhanced because of the Hall-Petch strengthening and strain strengthening.These results indicate that the ECDAP process is a promising approach for producing ultra-fine grains metallic materials.