Effect of globularization behavior of the lamellar alpha on tensile properties of Ti-17 alloy

In this work, the effects of processing parameters on microstructure evolution and tensile properties of Ti-17 alloy with a colony lamellar structure were investigated. For this purpose, a series of deformation and heat treatment experiments were conducted in the two-phase field. Microstructure observations indicated that the main feature of microstructure evolution during deformation and heat treatment is the globularization behavior of alpha phase. Furthermore, the globularization process was found to be prestrain dependent. The globularization fraction increased with the increasing of prestrain. In turn, tensile properties changed with the globularization fraction of alpha phase. The globularization behavior could refine the grain, decrease slip length and lead to a smoother alpha/beta interface. Such changes would improve tensile properties. Both strength and plasticity exhibited the increasing tendency with the globularization fraction. The quantitative investigations found that there are linear relationships between tensile properties and the globularization fraction. At both room temperature and 400 degrees C, tensile properties could be adjusted in the range of 1145-1258 MPa (RT)/945-990 MPa (400 degrees C) and 1068-1190 MPa (RT)/775-835 MPa (400 degrees C) for ultimate tensile strength and yield strength and 12-16% (RT)/13-17.5% (400 degrees C) and 19-31% (RT)/34-42% (400 degrees C) for elongation and reduction of area via varying the globularization fraction of alpha phase. These linear equations were determined by fitting the experimental data, respectively. The high correlation coefficients indicated that these equations could be used to represent the relationships between tensile properties and the globularization behavior for Ti-17 alloy. (C) 2016 Elsevier B.V. All rights reserved.