316L不锈钢表面激光熔化沉积CoCrNiCu中熵合金的界面相容性

Interfacial Compatibility for Laser Melting Deposition of CoCrNiCu Medium-Entropy Alloy on 316L Austenitic Stainless Steel Surface

异种材料界面相容性是制约结合强度的关键因素,然而其内在机制仍待完善。本工作开展了316L不锈钢表面激光熔化沉积CoCrNiCu中熵合金实验,借助SEM、STEM、EBSD、透射Kikuchi衍射(TKD)等手段对异种材料显微组织与界面特征进行表征,测试了异种材料界面力学性能,进而通过系统研究界面组织与晶体学相容性提出改善结合强度的方法。结果表明,CoCrNiCu中熵合金与316L不锈钢异种材料界面处形成了CoCrNiCuFe高熵合金全固溶过渡区,异种材料剪切强度可达324 MPa。在C元素界面配分引发奥氏体稳定性降低以及残余应力引发塑性变形的协同作用下,316L不锈钢靠近异种材料界面处的部分奥氏体晶粒发生应变诱导马氏体相变,这在促进相变诱导塑性(TRIP)效应的同时也会导致界面匹配程度降低。因此,对于物性差异较小的异种材料应保持相同晶体结构的单相匹配,通过提高界面晶体学相容性改善界面结合强度;对于物性差异较大的异种材料可借助TRIP效应设计双相结构以提高协调变形能力。

Dissimilar materials can achieve multifunction and multiperformance coupling and have broad development prospects in areas,such as aerospace,energy,automotive,and biomedicine.The properties of dissimilar materials can be improved by enhancing the compatibility of the heterogeneous interface.Herein,a laser melting deposition experiment of CoCrNiCu medium-entropy alloy(MEA)on the surface of 316L stainless steel was carried out.The microstructure morphology and interface characteristics of the dissimilar materials were characterized using SEM,STEM,EBSD,and transmission Kikuchi diffraction(TKD).The interfacial mechanical properties of the dissimilar materials were tested.The methods for promoting the bonding strength of dissimilar materials were then proposed by systematically exploring the interfacial compatibility of the microstructure and crystallography.The results show that a total solution transition zone of CoCrNiCuFe,a high-entropy alloy,was formed at the interface between CoCrNiCu MEA and 316L stainless steel.The shear strength of the dissimilar material can reach 324 MPa.Through the synergistic effect of austenite stability reduction caused by C interfacial partitioning and the plastic deformation induced by residual stress,some austenite grains of 316L stainless steel near the interface of the dissimilar materials undergo strain-induced martensitic transformation.This can promote the transformation-induced plasticity(TRIP)effect to improve the strength and ductility of the dissimilar materials while reducing interface matching.Therefore,as for the dissimilar materials with small physical discrepancies,single-phase matching with the same crystal structure should be maintained to increase the interfacial bonding strength by improving the interfacial crystallography compatibility.The TRIP effect can be used to design a duplex structure to improve the process of coordinated deformation for dissimilar materials with large physical discrepancies.