【作者】 吴达；

【导师】 安希忠； 邹清川；

【作者基本信息】 东北大学 ， 材料与化工， 2023， 硕士

【摘要】 钨铜复合材料已成为国防工业、国民经济建设和社会生活等领域的重要基础材料,并支撑着一大批高新技术产业的发展。相比于熔渗法,粉末冶金路线可制备任意钨铜颗粒混合比的钨铜复合材料。但如何实现钨铜颗粒混粉过程中堆积结构致密化设计和钨铜颗粒压实阶段颗粒重排过程颗粒锁死行为调控,成为高质量钨铜复合材料的实际开发和应用亟待解决的难题。基于此,本研究论文重点围绕钨铜复合材料致密化质量控制及其性能开展研究:首先从颗粒堆积角度入手,基于离散元方法研究钨铜颗粒大小及比例进行致密化颗粒堆积结构设计,对不同颗粒体制备的钨铜复合材料的力学性能及导电性进行综合评价,为钨铜复合材料均匀化制备提供颗粒选择依据;进一步,在最优堆积结构下进行W@20Cu复合颗粒压实阶段数值仿真,解析富铜区的形成原因和演化过程,研究稳定加载、循环加载和大压力对富铜区消除的影响,建立富铜区消除方法;在此基础上,从实验角度开发W@20Cu复合颗粒成分精确制备工艺,进行不同加载方式钨铜复合材料制备以实现高性能钨铜复合材料致密化质量控制及其性能评价。主要研究结果如下:(1)基于颗粒堆积结构的研究,二元堆积体系下,随着钨铜粒径比的增大,体系堆积密度增大,但在dW/dCu=1.5时其均匀性为最高0.986;为进一步提升体系堆积密度,由二元粒径扩展到三元粒径,通过配位数和堆积密度确定三元粒径为20wt.%时为最优堆积结构,此时致密度达到0.624;最优堆积结构下大/中/小颗粒对W-20Cu复合材料性能的影响表明:细小的W和Cu颗粒有利于Cu网络结构的形成,提高W颗粒与Cu基体烧结界面的结合能力,进一步有效地提高W-20Cu复合材料的烧结性能。(2)基于优化的钨铜颗粒堆积结构,建立W@20Cu复合颗粒的多粒子有限元压实及烧结模型,研究了烧结温度、压力加载方式对W@20Cu复合粉体压制致密化过程的影响规律。结果表明,颗粒重排是压坯前期主要致密化原因;当烧结温度为1000℃时,获得近乎全致密的烧结坯,核壳结构W@20Cu粉末制备的压坯内不存在W/Cu颗粒团聚的现象;高压加载制备的W@20Cu压坯应力集中,容易在压坯内部产生缺陷;循环加载与高压加载下压坯内部具有更加均匀的压实结构,但循环加载所得压坯内部应力分布均匀;相较于稳定加载,循环加载与高压加载可获得更加充分的颗粒间接触状态,有效地消除局部拱桥结构,避免产生富铜区。(3)成功开发核壳结构W@Cu复合颗粒成分准确的合成工艺,实现W@20Cu复合颗粒制备。研究烧结温度对W@20Cu复合材料组织和性能的影响,烧结温度为1000℃时,材料组织均匀,其抗拉强度为320 MPa,是普通结构W-20Cu复合材料的2.2倍。其破坏应变也从～3.4%升至～7.5%,提高了2.2倍。在最优烧结温度下进行W@20Cu复合颗粒压实阶段不同加载方式制备钨铜复合材料,发现循环加载和高压加载能很好地消除富铜区。其次,在最优振幅下,材料抗拉强度与断裂应变分别增至350 MPa和9.27%。同时,电导率增至39.06%IACS。高压加载脱模时压坯容易产生宏观裂纹,影响后续热压烧结阶段,导致材料抗拉强度急剧下降至160MPa,断裂应变低至4.45%。更多还原

【Abstract】 W-Cu composite materials have become an important basic material in fields such as national defense industry,national economic construction,and social life.It supports the development of a large number in high-tech industries.Compared with the infiltration method,the powder metallurgy route can prepare W-Cu composite materials with any mixing ratio of tungsten and copper particles.However,how to achieve the densification design of the packing structure during the mixing process of tungsten and copper particles and the regulation of particle locking behavior during the particle rearrangement process in the compaction stage has become urgent challenges for the practical development and application of high-quality W-Cu composites.The densification quality control and performance of W-Cu composite materials are focused.Firstly,we studied the structure of granular fillers about the size and proportion of tungsten and copper particles to design the dense packing structure based on the discrete element method.The mechanical properties and conductivity of W-Cu composite materials prepared with different particle systems are comprehensively evaluated.This provides a basis for particle selection about the uniform preparation of W-Cu composite materials;Furthermore,to analyze the formation reasons and evolution process of Cu-rich areas,we conducted numerical simulation on compaction stage under the optimal packing structure of W@20Cu composite particles.The effects of stable loading,cyclic loading,and high pressure on the elimination of Cu-rich areas are studied to establish a method for eliminating Cu-rich areas.The paper is based on this way to develop an experimental perspective of precise components preparation process of W@20Cu composite particle.The high-performance W-Cu composite materials are prepared with different loading methods to achieve densification quality control and performance evaluation.The main results are as follows:(1)Research are based on particle packing structure;In the binary packing system,the packing density increases with the increase of tungsten and copper particle size ratio.While the size ratio is 1.5,the uniformity is the highest at 0.986.The particle size are expanded from binary to ternary to further enhance the packing density of the system.It is the optimal packing structure when ternary particle size content achives 20wt.%by coordination number and bulk density,and the density reaches 0.624.The influence of large/medium/small particles on the properties of W-20Cu composite material under the optimal packing structure indicates that.Fine particles conducive to the formation of Cu-network structure and improve the bonding ability of tungsten particle and copper matrix sintering interface,and it further effectively improve the sintering performance of W-20Cu composites.(2)Based on optimized tungsten copper particle packing structure,we established W@20Cu multi-particle finite element compaction and sintering model for composite particles.We studied the effects of sintering temperature and pressure loading method on W@20Cu composite powder in compaction densification process.The results indicate that particle rearrangement is the main cause of densification in the early compaction stage.There is no agglomeration in the compact prepared by W@20Cu powders,and the sintered billets with core-shell are nearly fully dense when the sintering temperature is 1000℃.The highpressure loading concentrates stress in the W@20Cu billet,and it can easily cause defects inside the billet.There is a more uniform compaction structure inside the compacts under cyclic loading and high-pressure method,and the stress distribution is uniform inside the compacts.Compared with stable loading,cyclic loading and high-pressure loading can obtain a more complete contact state between particles,effectively eliminate local arch bridge structures and avoid the formation of copper rich areas.(3)Successfully developed a core-shell structure with accurate composition W@Cu composite particle synthesis process,and the W@20Cu composite particles are prepared.The effect of sintering temperature on W@20Cu composite materials structure and properties are studied.It gets an uniform structure when the sintering temperarure is 1000℃,and the tensile strength is 320 MPa,which is 2.2 times that of ordinary W-20Cu composite materials.The failure strain also increase from～3.4%to～7.5%with an increase of 2.2 times.The W@20Cu composite materials are prepared at the optimal sintering temperature with different loading methods during the compaction stage.It was found that cyclic loading can effectively eliminate copper rich areas.Secondly,at the optimal amplitude,the tensile strength and fracture strain of the material increase to 350 MPa and 9.27%,respectively.Meanwhile,the conductivity increases to 39.06%IACS.During high-pressure loading and demolding,the billet is prone to macroscopic cracks,which affects the subsequent hot pressing and sintering stage,and leads to a sharp decrease in the tensile strength to 160 MPa and a fracture strain as low as 4.45%.更多还原