Effect of Deformation Reduction on the Microstructure, Texture and Mechanical Properties of Forged Ti-6Al-4V

Author of the article:HUANG Lei, CHEN Yiwei, LIU Huaqiu, LI Fangling

Author's Workplace：Advanced Additive Manufacturing of Jihua Laboratory, Foshan 528000, China

Key Words：Ti-6Al-4V; anneal; mechanical properties; globular primary α

Abstract：The microstructure of commonly used forged Ti-6Al-4V mainly includes equiaxed, lamellar and bimodal structures. These structures and corresponding microstructure characteristics, such as grain size distribution, have a major impact on the tensile and fatigue properties of Ti-6Al-4V. However, there are few studies on the correlation between microstructure and mechanical properties under actual processing conditions(e.g., nonisothermal conditions and nonconstant strain rates). Based on this, the effect of nominal reduction during forging on the microstructures, tensile and fatigue properties of Ti-6Al-4V has been investigated in this paper. The microstructure of the initial material is a combination of equiaxed and lamellar α phases. With further deformation and annealing, the volume fraction of globular primary α increases by approximately 20% as the nominal reduction increases from 10% to 50%. More notably, the ultimate tensile strength and yield strength increase by ~50 MPa with the ductility remaining constant, which is attributed to the increase in the globular α phase volume fraction and decreasing alignment of the α phase basal planes with the tensile direction. The fatigue strength also increases with more nominal reductions. The significance of these observations is discussed in terms of the effect of an increased volume fraction of globular primary α on the bimodal microstructure after forging and annealing in Ti-6Al-4V