Effect of α Composite Layer on the Microstructure and Mechanical Properties of Ti-10V-2Fe-3Al Alloy

摘要:

通过在830 ℃空气中保温1 h后水冷的热处理工艺，在Ti-10V-2Fe-3Al(Ti1023) 钛合金表面形成厚度约为82 μm 的α富氧复合层。研究了α复合层内显微组织形貌、硬度及元素分布特点及复合α层后对Ti1023合金组织和性能影响。结果表明：α复合层从边缘到基体内部硬度值并非一直减小，而是呈现高-低-高-低-趋于稳定的变化规律。研究表明硬度变化规律与合金元素(尤其V、Fe)及组织形态分布相关。Ti1023合金试样复合α层后表面硬度增加了45%, 而屈服强度和抗拉强度下降5%。在拉伸变形过程中，复合α层后试样首先会在垂直于拉伸应力方向的外表面产生裂纹，之后裂纹扩展穿过α层到基体内部直至试样断裂，试样拉伸断口呈现心部韧性断裂和边部脆性断裂特征。拉伸过程中试样内部存在应力诱发β 相向α″相的组织转变。

Abstract:

Oxygen enriched α composite layer with 82 μm thickness was formed on the surface of Ti-10V-2Fe-3Al alloy by the heat treatment at 830 oC for 1 h in air and water quenching. The effects of α composite layer on the microstructure and mechanical properties of Ti-10V-2Fe-3Al alloy were investigated. The microstructure, the hardness and the elements distribution of α composite layer were studied. The results show that the hardness variation of α composite layer does not always display a decreasing trend from the edge to the matrix, but shows the law of high-low-high to stable trend, which is related with the distribution of elements (especially V and Fe) and microstructure evolution. The surface hardness of Ti-10V-2Fe-3Al alloy with α composite layer increases by 45%; meanwhile, the tensile strength and yield strength decrease by 5% only. Cracks will be generated firstly on the sample surface along the direction perpendicular to the tensile stress in tensile procedure, then expand in α composite layer and cross up to the matrix material. Fracture morphologies show the characters of ductility in matrix zone and brittle fracture in α composite layer zone. Stress induced phase transformation from β phase to α″ phase will take place during the tensile deformation.