Microstructure and Mechanical Properties of a Novel Ti-6.5Al-2Sn-4Zr-1.5Mo-2Nb-0.25Fe-0.2Si High-Temperature Titanium Alloy

• Published in: Materials science forum Vol. 993; pp. 351 - 357
• Main Authors: Hui, Song Xiao, Zhang, Wen Jing, Song, Xiao Yun, Diao, Yu Wei, Zhao, Ming Yu, Ye, Wen Jun
• Format: Journal Article
• Language: English
• Published: Pfaffikon Trans Tech Publications Ltd 01.05.2020
• Subjects: Annealing; Beta phase; Ductile fracture; Electron backscatter diffraction; Electron probe microanalysis; Electron probes; Elongated structure; Heat resistant alloys; Heat treating; Heat treatment; Lamellar structure; Mechanical properties; Microstructure; Optical properties; Phase transitions; Room temperature; Tensile tests; Titanium alloys; Titanium base alloys; Mechanical Properties; Heat Treatment; Microstructure; Fe Element; High Temperature Titanium Alloy
• ISSN: 0255-5476; 1662-9752; 1662-9752
• DOI: 10.4028/www.scientific.net/MSF.993.351

The Ti-6.5Al-2Sn-4Zr-1.5Mo-2Nb-0.25Fe-0.2Si (wt%) alloy is a novel two-phase high temperature alloy for short-term application. The effects of different heat treatments on the microstructure and mechanical properties were investigated through electron probe microanalysis (EPMA), optical microcopy (OM), scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and tensile tests at room temperature and 650°C. Subjected to the annealing treatment at α+β region (1010 °C/2 h, FC to 990 °C+990 °C/2 h, AC), the microstructure was composed of bimodal structure, which consists of equiaxed primary α (αp) phase and lamellar transformed β (βt) structure. As a strong β stabilizer, the content of Fe in α phase is much less than that in β phase. Annealing at β region (1040 °C/2 h, AC) resulted in the formation of widmannstatten structure, consisting of coarse raw β grain and secondary α phase precipitated on the β grain. With respect to the tensile property, different heat-treated alloys obtained similar strength. However, widmannstatten structure was characterized by lower plasticity, with the elongation only half that of bimodal structure. The fracture characteristics at room temperature for the alloy with bimodal structure and widmannstatten structure are dominated by ductile fracture and cleavage fracture, respectively.