Texture evolution during sub-critical annealing and its effect on yield strength anisotropy of laser directed energy deposited Ti-6Al-2Zr-1Mo-1V alloy

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 850; p. 143556
• Main Authors: Li, Renkai, Wang, Huaming, Zheng, Dongdong, Gao, Xu, Zhang, Shuquan, Cheng, Xu, He, Bei
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 11.08.2022; Elsevier BV
• Subjects: Anisotropy; Annealing; Deposition; Evolution; Horizontal orientation; Laser directed energy deposition; Mechanical properties; Sub-critical annealing; Texture; Titanium alloys; Titanium base alloys; Yield strength; Yield strength anisotropy; Yield stress; Titanium alloys; Sub-critical annealing; Yield strength anisotropy; Laser directed energy deposition; Texture
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.143556

Titanium alloys fabricated by laser directed energy deposition (LDED) are usually subjected to sub-critical annealing to improve mechanical properties. This work mainly investigated the texture evolution of LDEDed Ti–6Al–2Zr–1Mo–1V alloy during sub-critical annealing and its effect on the anisotropy of yield strength. Results indicated that of α phase in the as-deposited sample exhibited two types of circle-shaped texture, which were perpendicular to the deposition direction (VD) and 45° away from VD, respectively. The intensities of these two types of texture were approximately equal because the α texture in the as-deposited sample were transformed from the strong β//VD fiber texture following Burgers orientation relationship with weak variant selection. During sub-critical annealing, the formation of primary α phase, which tended to be transformed from the {110}β parallel to VD, led to the intensity of circle-shaped texture perpendicular to VD greater than that 45° away from VD. The calculation results suggested that all basal and prismatic slip systems of some α variants transformed from the {110}β parallel to VD were in hardly-activated orientation with Schmid factor (m) equal to zero for loading along the horizontal direction (HD), the slip systems of some α variants transformed from the {110}β 45° to VD were in hardly-activated orientation with m = 0 for loading along 45° direction (OD), while the systems of all α variants were in easily-activated orientation with high Schmid factors for loading along VD. After sub-critical annealing, the content of α phase in hardly-activated orientation increased for loading along HD but decreased for loading along OD, resulting in a smaller difference of yield strength between OD and VD or HD. •LDEDed Ti–6Al–2Zr–1Mo–1V alloy exhibited two types of circle-shaped α texture.•The relative content of the two types of texture was the key factor to affect the anisotropic yield strength.•The activation for slip systems of all possible α variants was analyzed.•Sub-critical annealing reduced the anisotropy of yield strength.