【作者】 张明；

【导师】 梁淑华； 姜伊辉；

【作者基本信息】 西安理工大学 ， 材料加工工程， 2022， 硕士

【摘要】 第二相颗粒对铜基体晶格常数影响较小且与基体的位错和晶界具有良好的交互作用,因此铜基复合材料有望解决导电性与强度不兼容的问题而被广泛研究。本研究基于球磨工艺对前驱体粉末的影响,以不锈钢球磨材质与刚玉球磨材质为主要变量,利用粉末冶金法制备3 wt.%TiB2/Cu复合材料,并对其进行热挤压及冷轧变形处理。研究了球磨材质对复合材料传导性能和力学性能的影响、球磨时间对前驱体粉末晶粒尺寸影响、退火孪晶形成机理及作用和热挤压与冷轧对铜基体取向与织构的影响。主要研究结果如下:(1)球磨材质对TiB2/Cu复合材料导电性能的影响机制为不同类型的球磨杂质对铜基体的作用不同。根据导电理论,不锈钢球磨材质球磨引入的Fe原子固溶在铜基体中破坏了铜基体的晶格完整性,从而影响自由电子定向移动,大幅降低了 TiB2/Cu复合材料的导电性能。而刚玉材质球磨引入的Al2O3杂质在铜基体中不固溶对铜晶格影响较小,因而对TiB2/Cu复合材料的导电性能影响较小。不锈钢材质球磨热挤压态复合材料导电率为39.7%IACS,刚玉材质球磨热挤压态复合材料导电率提升至78.7%IACS。(2)不锈钢材质球磨热挤压态复合材料由于TiB2颗粒对晶界良好的钉扎作用,具有良好的高温稳定性。室温抗拉强度可达到566.3 MPa,600℃时抗拉强度为129.7 MPa。高温软化温度可达到1050℃以上,300次热疲劳实验后硬度仍保持在150 HBW左右。刚玉材质球磨热挤压态复合材料抗拉强度为370 MPa,经过冷轧处理后复合材料抗拉强度提升至 500 MPa。(3)球磨时间对前驱体粉末的影响主要是铜基体的晶粒细化以及前驱体粉末混合均匀程度。铜基体晶粒的细化作用发生在球磨前20 h,前10 h晶粒细化效果最明显,20 h后球磨对铜基体晶粒细化效果不明显。前驱体粉末在球磨中过程中未发生机械合金化。(4)由于变形过程中晶粒取向的变化,烧结态TiB2/Cu复合材料经热挤压变形后生成强Goss织构,冷轧变形后热挤压态TiB2/Cu复合材料由Goss织构演化为Brass织构。Goss织构增加了热挤压态TiB2/Cu复合材料的施密特因子,Brass织构降低了冷轧态TiB2/Cu复合材料的施密特因子。轧制态与热挤压态TiB2/Cu复合材料均保持较高的施密特因子,处于软取向。(5)冷轧态TiB2/Cu复合材料基体晶粒尺寸细小,单个晶粒变形能力有限,主要变形方式为相邻晶粒间的协调变形。铜基体晶界上分布的TiB2颗粒降低了 TiB2/Cu复合材料晶粒间的协调能力。更多还原

【Abstract】 The second phase particles have little effect on the lattice constant of the copper matrix and have a good interaction with the dislocations and grain boundaries of the matrix.Therefore,copper matrix composites are expected to solve the problem of incompatibility between electrical conductivity and strength.In this study,based on the influence of the ball milling process on the precursor powder,with stainless steel ball milling medium and corundum ball milling medium as the main variables,3 wt.%TiB2/Cu composites were prepared by powder metallurgy,and then hot extrusion and cold rolling were carried out.In this paper,the effects of ball milling medium on the conductivity and mechanical properties of composites,the effect of ball milling time on the grain size of precursor powder,the formation mechanism and effect of annealing twins,and the effects of hot extrusion and cold rolling on the orientation and texture of copper matrix were studied.The main findings are as follows:(1)The influence mechanism of the ball-milling material on the electrical conductivity of TiB2/Cu composites is that the different types of ball-milling impurities have different effects on the copper matrix.The introduction of Fe atoms into the copper matrix by ball milling of stainless steel destroys the integrity of the matrix lattice,thereby affecting the directional movement of free electrons and greatly reducing the electrical conductivity of TiB2/Cu composites.The Al2O3 impurity introduced by corundum ball milling is difficult to dissolve into the copper matrix and has little effect on the copper lattice,which has little effect on the electrical conductivity of the TiB2/Cu composite.The conductivity of the stainless steel ball-milled composite with hotextrusion is 39.7%IACS,and the conductivity of the corundum-based ball-milled composite with hot-extrusion is increased to 78.7%IACS.(2)The stainless steel ball-milled composite with hot-extrusion has good high temperature stability.The tensile strength at room temperature can reach 566.3 MPa,and the tensile strength at 600℃ is 129.7 MPa.The softening temperature at high temperature can reach above 1050℃,and the hardness remains around 150 HBW after 300 thermal fatigue tests.The tensile strength of the corundum ball-milled hot-extruded composite material is 370 MPa,and the tensile strength of the composite material is increased to 500 MPa after cold rolling treatment.(3)The influence of the ball milling time on the precursor powder is mainly the grain refinement of the copper matrix and the mixing uniformity of the precursor powder.The grain refinement of copper matrix occurred 20 h before ball milling,and the grain refinement effect was the most obvious in the first 10 h,and the effect of ball milling on copper matrix grain refinement was not obvious after 20 h.The precursor powder was not mechanically alloyed during ball milling.(4)The sintered TiB2/Cu composites formed strong Goss texture after hot extrusion deformation,and the hot extrusion TiB2/Cu composites evolved from Goss texture to Brass texture after cold rolling deformation.Goss texture increases the Schmidt factor of hot-extruded TiB2/Cu composites,and Brass texture reduces the Schmidt factor of cold-rolled TiB2/Cu composites.Both the as-rolled and hot-extruded TiB2/Cu composites maintain a high Schmidt factor.(5)The grain size of the matrix of the cold-rolled TiB2/Cu composite material is small,and the deformation capacity of a single grain is limited.The main deformation mode is the coordinated deformation between adjacent grains.The TiB2 particles distributed on the grain boundaries of the copper matrix reduce the coordination ability between the grains of TiB2/Cu composites.更多还原