具有优异拉伸性能的新型铸态富Ti难熔高熵合金

Novel as-cast Ti-rich refractory complex concentrated alloys with superior tensile properties

难熔高熵合金因其优异的高温屈服强度和抗软化性能而备受关注.然而,室温延展性差和较高的密度目前仍然是其加工以及应用需要面临的主要挑战.本文利用材料的固有特性作为合金设计原则,通过调控Mo浓度,制备了三种新型单相体心立方结构的Ti3Zr1.5Nb((1-x))-MoxVAl_(0.25)(x=0.1,0.3,0.5,标记为Mo0.1,Mo0.3和Mo0.5)合金,这些合金都具有良好的拉伸延展性和低于6 g cm^(-3)的密度.高剪切模量Mo元素的引入促进了晶格畸变,从而提高了合金中的晶格摩擦应力以及屈服强度.铸态Mo0.3和Mo0.5合金均表现出超过1100 MPa的拉伸屈服强度,以及大于15%的断裂延伸率.Labusch模型计算结果表明,原子尺寸和剪切模量失配引起的固溶强化对屈服强度的影响最为显著.通过观察变形微观组织发现,由于存在高密度的位错界面,扭折带、位错壁以及泰勒晶格的形成能有效提高合金的应变硬化能力,使合金在展现高强度的同时保持足够的延展性.该研究为开发具有高强韧的单相难熔高熵合金提供了新的见解.

Refractory complex concentrated alloys(RCCAs)have drawn particular attention for their high yield strength and superior softening resistance at high tempera-tures.However,poor room-temperature ductility and high density remain the main challenges for their processing and applications.Here,using inherent material characteristics as the alloy-design principles,three novel single-phase body-centered cubic structured Ti_(3)Zr_(1.5)Nb_(1-x)Mo_(x)VAl_(0.25)(x=0.1,0.3,0.5,marked as Mo0.1,Mo0.3,and Mo0.5,respectively)RCCAs with promising tensile ductility and relatively low density below 6 g cm^(-3) were developed by tailoring the Mo concentration.The introduction of Mo elements with high shear modulus promotes lattice distortion,contributing to enhanced lattice friction stress and yield strength.The Mo0.3 and Mo0.5 alloys exhibit tensile yield strengths exceeding 1100 MPa and high fracture elongation of over 15%in the as-cast state.Labusch’s model revealed that solid-solution strengthening induced by atomic size and shear modulus mismatch contributes most significantly to yield strength.Deformation microstructure observations uncovered that the formation of the kink bands,dense-dislocation walls,and Taylor lattices are highly effective in enhancing strain-hard-ening capacity due to their high density of dislocation boundaries,enabling the alloys to maintain high strength while yet ensuring enough ductility.This study provides new insights into the development of strong and ductile RCCAs with single-phase structures.