高压扭转变形缺陷对钨铜扩散焊显微组织和力学性能的影响

Effect of Lattice Defects Induced by High-Pressure Torsion on Microstructure and Mechanical Properties of W/Cu Composite Materials Processed by Diffusion Welding

对商业纯钨和铜铬锆合金在900~980℃进行压力80 MPa、时间2 h的真空扩散焊(diffusion welding,DFW)试验,并对扭转圈数为5~20圈的高压扭转(high-pressure torsion,HPT)变形钨和铜合金进行900℃真空扩散焊试验,获得了界面连接结合良好、力学性能优良的钨铜复合材料。借助OM、EDS和XRD,对比分析了高压扭转引入的晶体缺陷对扩散焊后钨和铜元素扩散、显微组织和显微硬度的影响规律。结果表明,随着真空扩散焊温度升高,钨和铜的元素扩散深度分别由(0.4±0.1)μm和(0.9±0.1)μm逐渐提升至(0.9±0.1)μm和(1.7±0.2)μm,高温导致晶粒组织异常长大,显微硬度显著下降。HPT变形引入的高密度位错和超细晶组织促进扩散焊过程中的原子扩散与迁移,20圈变形扩散焊试样的钨和铜元素扩散深度达到(2.4±0.1)μm和(3.1±0.2)μm,较初始态提升了5倍和2.4倍;钨变形组织在扩散焊后得到有效保留,条带状晶粒有限长大至62μm×25μm,位错密度约为1.46×10^(14 ) m^(-2),较初始态高32.7%;铜合金在高温扩散焊后呈现退火孪晶和等轴晶的粗大混晶组织,高温再结晶使其位错密度回复至初始态。高压扭转变形后扩散焊后钨的显微硬度(HV0.5)和铜铬锆的显微硬度(HV0.1)分别为4596~4635 MPa和608~715 MPa,较初始态扩散焊提升了48%和9%,表明该工艺为制备高性能钨铜复合材料的有效手段。

Commercial pure tungsten and CuCrZr alloy were treated at 900-980℃for 2 h under the pressure of 80 MPa by the diffusion welding(DFW)processing.The tungsten and CuCrZr alloy after high-pressure torsion(HPT)process with 5-20 turns were also treated by DFW at 900ºC,and the W/Cu composite materials with good interfacial bonding and mechanical properties were obtained.The effects of lattice defects induced by HPT on the element diffusion,microstructure evolution,and microhardness were analyzed by OM,EDS,and XRD.Results show that the diffusion depth for W and Cu is increased from(0.4±0.1)μm and(0.9±0.1)μm to(0.9±0.1)μm and(1.7±0.2)μm with increasing of the DFW temperature,respectively,and the high temperature leads to the obvious grain coarsening and the reduction in microhardness.The high-density dislocations and ultrafine grains induced by HPT accelerate the element diffusion and immigration during DFW.After 20 turns of HPT followed by DFW,the diffusion depth for W and Cu reaches(2.4±0.1)and(3.1±0.2)μm,which is 5 times and 2.4 times higher than that of the initial state,respectively.The deformation microstructure of tungsten remains after DFW with slight grain growth to 62μm×25μm and the dislocation density is about 1.46×10^(14 ) m^(-2),which is 32.7%higher than that of the initial state.The coarse mixture microstructure of CuCrZr alloy after DFW with HPT is composed of annealing twinning grains and equiaxed grains,and the high temperature of DFW leads to the complete recovery of dislocations accumulated by HPT.The microhardnesses(HV0.5 and HV0.1)of W and CuCrZr after DFW with HPT is 4596-4635 and 608-715 MPa,which are 48%and 9%higher than that of the value of initial sample after DFW,respectively.The results illustrate that HPT processing followed by DFW is beneficial to fabricate W/Cu composite materials of high performance.