Influence of multi-stage heat treatment on the microstructure and mechanical properties of TC21 titanium alloy

• Published in: International journal of minerals, metallurgy and materials Vol. 28; no. 2; pp. 296 - 304
• Main Authors: Long, Wei, Zhang, Song, Liang, Yi-long, Ou, Mei-gui
• Format: Journal Article
• Language: English
• Published: Beijing University of Science and Technology Beijing 01.02.2021; Springer Nature B.V; Key Laboratory for Materials Structure and Strength of Guizhou province, Guizhou University, Guiyang 550025, China; National Local Joint Engineering Laboratory for High Performance Metal Structure Materials and Manufacturing Technology, Guizhou University, Guiyang 550025, China; College of Materials and Metallurgy, Guizhou University, Guiyang 550025, China
• Subjects: Aging; Air cooling; Alloying elements; Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Composites; Cooling; Cooling rate; Corrosion and Coatings; Crack propagation; Elongation; Glass; Heat treatment; High temperature; Liquid cooling; Low temperature; Materials Science; Mechanical properties; Metallic Materials; Natural Materials; Nucleation; Phases; Solution heat treatment; Surfaces and Interfaces; Tensile deformation; Tensile strength; Thin Films; Titanium alloys; Titanium base alloys; Tribology; multi-stage heat treatment; titanium alloy; tension; microstructure; mechanical properties; in-situ tension
• ISSN: 1674-4799; 1869-103X
• DOI: 10.1007/s12613-020-1996-1

Duplex-structured TC21 alloy samples were first solution-treated at a higher temperature in the α + β region (940°C) with furnace cooling (FC), air cooling (AC), and water cooling (WC), followed by a second-stage solution treatment at a lower temperature in the α + β region (900°C), and then finally aged at 590°C. The effects of the morphology and quantity of α phases on the structure and properties of the TC21 alloy after the different heat treatments were analyzed. The in-situ tensile deformation process and crack propagation behavior were observed using scanning electron microscopy (SEM). The quantity of equiaxed α phases as well as the thickness of lamellar α phases reduced, the tensile strength increased firstly and then decreased, the elongation decreased with the increasing cooling rate after the first-stage solution treatment. The amount and size of lamellar α phases increased after the second-stage solution treatment because of sufficient diffusion of the alloying elements, thereby leading to increased tensile strength. The amount of dispersed α phases increased after the third-stage aging treatment owing to the increase in the nucleation rate, resulting in a noteworthy strengthening effect. After the third-stage aging treatment, the first-stage FC sample exhibited better mechanical properties because it contained more equiaxed α and β trans phases than the first-stage AC and WC samples.