Microstructural characterization of laser melting deposited Ti–5Al-5Mo–5V–1Cr–1Fe near β titanium alloy

• Published in: Journal of alloys and compounds Vol. 572; pp. 17 - 24
• Main Authors: Liu, C.M., Tian, X.J., Tang, H.B., Wang, H.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25-09-2013; Elsevier
• Subjects: Bands; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Grains; Hardness; Laser beam melting; Laser deposition; Laser processing; Macrostructure; Materials science; Mechanical and acoustical properties; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals and alloys; Methods of deposition of films and coatings; film growth and epitaxy; Microstructure; Physical properties of thin films, nonelectronic; Physics; Reheating; Solubility, segregation, and mixing; phase separation; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Tribology and hardness; Laser processing; Microstructure; Metals and alloys; Material processing; Segregation; Cooling rate; Temperature gradients; Laser deposition; Laser assisted processing; Mechanical properties; High temperature; Hardness; Melting points; Titanium alloys; Morphology; Bamboo structure; Heat affected zone; Laser fusion; Macrostructure; Formation mechanism
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.03.243

•Laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe near β titanium alloy was achieved.•Macrostructure, microstructure and hardness were investigated.•Four microstructure characteristics were observed.•The formation process of the novel β grain morphology was demonstrated.•The formation mechanism of layer bands was discussed and proposed.
Laser melting deposition (LMD) is characterized by high temperature gradients, high cooling rates and reheating treatment effects. These features of LMD generally lead to an unique microstructure. In this study, the macrostructure, microstructure and hardness of laser melting deposited Ti–5Al–5Mo–5V–1Cr–1Fe near β titanium alloy have been investigated. The macrostructure is characteristic of novel β grain morphology and layer bands. The β grains exhibit successive alternation of large columnar and bamboo-like grain morphology, which is associated with the LMD processing parameters. Layer bands exhibit duplex microstructure and low hardness, while ultra-fine basket-weave microstructure, microsegregation and high hardness are observed between layer bands. Microstructure and hardness of the alloy are non-uniform due to the existence of the layer bands. Thus, special attention is given to the formation mechanism of layer bands. It is found that layer bands are heat-affected zones which resulting from the sub-melting-point reheating treatment when a new layer deposits.