高速冲击条件下粉末冶金难熔高熵合金的绝热剪切变形机制研究

Refractory high entropy alloy (RHEA) is an ideal armor-piercing (AP) material with good self-sharpening capability, mainly due to its high density and high adiabatic shear sensitivity. Powder metallurgy has advantages of homogenizing compositions and refining microstructures in the processing of refractory multi-principal component alloys. However, at present, there are few reports on adiabatic shear deformation behavior of powder metallurgical RHEAs under dynamic deformation condition. This research will prepare fully dense and fine-grained powder metallurgical WMoTaNb-Ti RHEAs through canned hot extrusion. And then, study the mechanical response and adiabatic shear deformation behavior of the RHEAs under high velocity impact. The aim of this study is to reveal the effecting mechanism of multiple components as well as microstructural features on the formation and propagation of adiabatic shear bands. Also, this study will try to propose compositional and microstructural design principles for powder metallurgical RHEAs to gain high adiabatic shear sensitivity. The project will provide technical support for the design and preparation of novel high-performance AP materials and promote the theoretical development of dynamic deformation in the fields of powder metallurgical RHEAs.

难熔高熵合金具有高密度、高绝热剪切敏感性特征，是理想的高自锐性穿甲弹芯材料。粉末冶金技术在制备多主元难熔合金方面有成分均匀、组织细小的优势。但是，目前针对粉末冶金难熔高熵合金的绝热剪切变形行为研究还鲜有报道。项目以难熔高熵合金WMoTaNb为研究对象，以Ti合金为粘结相，通过粉末包套热挤压形成全致密、准纤维细晶结构的粉末冶金难熔高熵合金材料。然后，研究高速冲击条件下材料的力学响应及绝热剪切变形行为，阐明多主元成分及结构特征对绝热剪切带形成与扩展的影响机制，形成高绝热剪切敏感性的粉末冶金难熔高熵合金成分及微结构设计原则。研究成果将为新型高自锐性穿甲弹芯材料的设计与制备提供基础支持，并推动多主元合金动态变形相关理论的发展。

本项目开展了难熔高熵合金粉末的制备及致密化、粉末冶金高熵合金热挤压变形调控微结构、高熵合金动态变形行为及绝热剪切机制等研究，实现了粉末冶金高熵合金准静态性能和动态冲击性能的提升，揭示了粉末冶金高熵合金的动态变形机制，阐明了绝热剪切带演化规律。所取得的的创新性成果如下：. （1）开发了喷雾造粒结合等离子球化制备难熔高熵合金粉末的新方法，并通过快速热压成功制备了高性能、全致密难熔高熵合金材料。. （2）阐明了粉末冶金高熵合金在热挤压变形过程中的组织演变规律，通过挤压变形调控高熵合金组织形态及相结构，实现了强度与塑性的协同提升。研制的粉末冶金高熵合金室温压缩屈服强度可达937MPa，室温压缩塑性达44%，600℃高温强度仍有500MPa以上。. （3）揭示了粉末冶金高熵合金在动态变形过程中存在位错滑移、层错和变形孪晶等变形行为，阐明了多种变形行为协同作用消散冲击应变能从而实现动态性能提升的机制。. （4）揭示了粉末冶金高熵合金绝热剪切带附近存在等轴晶-伸长晶-超细晶的梯度微结构，阐明了剪切带内超细晶的形成是亚晶在极短的时间内通过旋转动态再结晶机制作用的结果。. 以上发现对于理解粉末冶金高熵合金的动态力学行为及绝热剪切变形机制等方面具有重要科学意义，对于指导高熵合金微结构设计及性能优化方面具有重要理论价值。通过以上研究，在Journal of Alloys and Compounds、Materials Characterization等国际权威期刊发表学术论文5篇；申请发明专利1项，参加国内学术会议并作特邀报告2次。.