基于TRIP效应的BCC高熵合金韧塑化机理研究

High entropy alloys (HEAs) have been emerging as a new class of metallic materials over the last decade, and have a great potential to be utilized as next-generation structural materials due to their excellent mechanical properties over a wide range of temperature and severe circumstances. HEAs with body-centered cubic (BCC) structure exhibit high strength, hardness, good wear-resistance, but suffer from their room-temperature brittleness and poor machinability. To address this challenge, this project will introduce the concept of “transformation-induced plasticity” (TRIP) into BCC HEAs and investigate the ductilization mechanism. Firstly, phase stability and forming requirements of metastable parent phase in BCC HEAs will be clarified. On basis of this, BCC HEAs with metastable phase undergoing deformation-induced displacive transformation will be fabricated, aiming to enhance ductility while preserve the high strength of BCC HEAs. And then, the phase transformation behavior in the BCC HEAs with high configuration entropy and chemical disorder will be characterized. The effects of ordering parameter on energy state of the parent and product phases and transformation path will be elaborated. Furthermore, the local stress/strain partition and cooperative deformation between the transformable and the un-transformable phases will be studied, from which the ductilization mechanism of TRIP effect in BCC HEAs will be revealed. The implement of the proposed research will not only develop TRIP-reinforced high performance BCC HEAs which can broaden real engineering application of HEAs, but also reveal intrinsic mechanism of deformation-induced phase transformation and TRIP effect in HEAs, enrich theory of phase transformation in solid-state materials.

高熵合金是最近发展起来的一类新型金属材料，能够在宽温域及多种极端条件下表现出优异的力学性能，有望成为新一代的高性能结构材料。尤其BCC结构的高熵合金具有高的室温强度、硬度、耐磨性和优异的高温力学性能，但通常表现为室温脆性，加工性能较差。基于此，本申请拟在BCC高熵合金中引入“相变诱导塑性”（TRIP）效应，对脆性BCC高熵合金进行韧塑化。通过研究其相稳定性的影响因素，揭示亚稳母相的生成条件和调控机理。同时，研究高构型熵和化学无序条件下的形变诱导相变特点，阐明序参量对高熵合金母、子相能量状态和相变路径的影响，揭示BCC高熵合金母相变形、相变、子相变形的序列和应力、应变配分特点，从而阐明其形变、相变的交互作用机理和韧塑化机制。本项目的完成一方面有利于开发出高韧塑性高熵合金，拓宽高熵合金的实际工程应用前景，另一方面会揭示高熵合金中形变诱导相变和TRIP效应的内禀机理，丰富固体材料的相变理论。

高熵合金是最近发展起来的一类新型金属材料，能够在宽温域及多种极端条件下表现出优异的力学性能，有望成为新一代的高性能结构材料。尤其体心立方（BCC）结构的高熵合金具有高的室温强度、硬度、耐磨性和优异的高温力学性能，但通常表现为室温脆性，加工性能较差。本项目针对BCC高熵合金室温脆性，加工性能较差等问题，引入“相变诱导塑性”（TRIP）效应，对脆性BCC高熵合金进行韧塑化，研究了其相稳定性的影响因素，揭示了亚稳母相的生成条件和调控机理。同时，研究了高构型熵和化学无序条件下的形变诱导相变特点，阐明了序参量对高熵合金母、子相能量状态和相变路径的影响，揭示了BCC高熵合金母相变形、相变、子相变形的序列和应力、应变配分特点，阐明了其形变、相变的交互作用机理和韧塑化机制。具体包括以下几方面的研究工作：1）系统研究了BCC高熵合金中的相稳定性和亚稳母相生成条件；2）阐明了BCC高熵中形变诱导相变内禀特征及调控机理；3）揭示了TRIP韧塑化BCC高熵合金的力学行为特点及形变相变交互作用机制；4）分析了BCC高熵合金中层错能的影响因素及与宏观性能的关联；5）扩展了短程序的概念，着重阐述短程序对高熵合金力学性能的影响；6）深入分析了局部化学涨落对位错成核和运动的影响。在以上研究成果的基础上，本项目发表学术论文43篇，其中SCI论文43篇，JCR一区论文37篇，申请专利28项。