高压扭转制备钨铜复合材料的微观组织及显微硬度演化规律

Microstructure and Microhardness Evolution of W-Cu Composites Prepared by High- pressure Torsion

摘要:

基于传统高压扭转工艺，引入浮动凹模技术，开发了适用于性能高差异的钨与铜合金浮动凹模压扭成形工艺(high-pressure torsion, HPT)，在300℃、1.5GPa条件下获得了界面结合良好的高性能钨铜复合材料。借助金相显微镜(optical microscope, OM)、X射线衍射技术(X-ray diffraction, XRD)和扫描电子显微镜(Scanning electron microscope, SEM)分析了大剪切变形过程中晶粒细化和位错累积对界面元素扩散和显微硬度的影响。结果表明：随着扭转圈数和扭转半径的增加，钨组织由粗大等轴晶被拉长、破碎、细化呈流线状，20圈变形试样的平均晶粒尺寸被细化至9.0±2μm，在持续剪切细化的作用下，位错密度不断上升至3.4×1014 m-2，较初始试样提升了2.9倍；铜铬锆合金的晶粒细化基本接近饱和，组织呈现平均尺寸约为0.3-1.5μm的细小等轴晶，大应变导致的动态再结晶促使其位错密度维持动态平衡，约为2×1014 m-2。变形产生的高密度晶界和位错，促进了钨和铜在界面处的元素互扩散，并且随着扭转圈数的增加，钨元素和铜元素的扩散深度分别由1.2μm和2.9μm增加至1.6μm和6.2μm。在细晶强化和位错强化的共同作用下，钨和铜铬锆合金的显微硬度较初始试样均得到显著提升，20圈变形试样的平均显微硬度分别约为548.3±36Hv0.5和125.0±4Hv0.1。

Abstract:

Based on the traditional high-pressure torsion process and the introduction of floating die technology, a high pressure torsion (HPT) process for tungsten and copper alloys with high performance differences was developed. High performance tungsten copper composite materials with good interface bonding were obtained at 300 ℃ and 1.5GPa. The effects of grain refinement and dislocation accumulation on interfacial element diffusion and microhardness during large shear deformation were analyzed by X-ray diffraction (XRD)、optical microscope (OM) and scanning electron microscope (SEM). The results show that with the increase of HPT turns and torsion radius, the equiaxed coarse grains of tungsten are elongated and refined to streamline shape with the average size of 9.0±2 μm after 20 turns and the dislocation density increases to 3.4 × 1014 m-2, which is 2.9 times higher than the initial sample due to the shear deformation. The grain refinement of copper is almost saturated, and equiaxed ultrafine grains with the average size of about 0.3-1.5 μm were obtained within 20 turns of HPT processing. The dislocation density keeps dynamic equilibrium at about 2×1014 m-2 due to the dynamic recrystallization caused by large shear strain. The high-density grain boundaries and dislocations produced by large shear deformation promote the mutual diffusion of tungsten and copper at the interface. With the increase of HPT turns from 10 to 20, the diffusion depth of tungsten and copper increase from 1.2μm and 2.9μm to 1.6 μm and 6.2 μm respectively. Under the effect of grain refinement and dislocation accumulation, the microhardness of tungsten and copper is significantly enhanced to 548.3 ± 360 Hv and 125.0 ± 4 Hv respectively.