The effect of microstructure on tensile properties, deformation mechanisms and fracture models of TG6 high temperature titanium alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2011-03, Vol.528 (6), p.2370-2379
• Main Authors: Wang, Tao, Guo, Hongzhen, Wang, Yanwei, Peng, Xiaona, Zhao, Yan, Yao, Zekun
• Format: Article
• Language: English
• Subjects: Applied sciences; Colonies; Crack propagation; Deformation; Deformation mechanism; Dislocation; Elasticity. Plasticity; Exact sciences and technology; Fracture mechanics; Fracture model; Fractures; Lamella; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Scanning electron microscopy; Slip; Tensile properties; TG6 titanium alloy
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2010.12.044

▶ Fine α hindered dislocation slip and crack nucleation and decreased crack propagation velocity. ▶ α lamellae decided the type and amount of slip system and the crack propagation. ▶ Fine α lamellae promoted the deformation coordination and the start of new slip systems. ▶ The fracture model of the samples with bimodal microstructure was not sensitive to α lamellae. ▶ Fracture model with the bimodal microstructures was a mixture fracture at room temperature. The tensile properties at room temperature and 600°C of TG6 titanium alloy with different microstructures {bi-modal microstructures with thick α lamella (BTL) and fine α lamella (BFL), and a mixed microstructure with different morphologies of α phase} were obtained. It was found that the BFL microstructure possessed the highest tensile strength, and the elongations of the BTL and BFL microstructures were almost the same of about 13% at room temperature and 17% at 600°C, respectively. In addition, the mixed microstructure had the lowest plasticity. The tensile deformation mechanisms of α lamella (αL), primary α phase (αp), equiaxed α phase (αe) and α colonies were researched by the analysis of respective dislocation morphologies. Notably, the accommodative deformations through grain/phase boundaries sliding determined the deformation models of αL, αp, and αe. Compared to the thick αL and α colony, the fine αL and α colony activated more slip systems due to their excellent accommodative deformation capability. Furthermore the deformation mechanisms at room temperature and 600°C were different from each other. Scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and transmission electron microscopy (TEM) were used to research the crack propagation paths and fracture models. Crack propagation path crossing α colonies and αp were discussed, respectively. The colonies boundaries, αp/colonies boundaries, αe/αe boundaries and silicide were found to be the stress concentration locations. The micro-plasticity of tensile specimens determined the fracture morphologies and fracture models.