The Effect of α-Phase Grains Morphology in Initial Microstructure on Superplasticity of Two-Phase Titanium Alloys

Abstract:

It is generally accepted that fine-grained and equiaxed microstructure enables superplastic deformation of two-phase titanium alloys. Appropriate microstructure is usually developed in the thermomechanical processing with careful selection of the parameters of plastic deformation and heat treatment. Based on results of own research in this area increased superplasticity was found in Ti6Al4V alloy having microstructure containing highly deformed and elongated α-grains – considerably different from equiaxed ones. It was found that during heating up and first stage of superplastic deformation fragmentation of elongated α-phase grains occurred, followed by formation and growth of globular grains of that phase. Particular role of quenching of the Ti6Al4V alloy from the stable β-phase temperature range in thermomechanical processing was identified. It leads to increase of elongation coefficient of α-phase grains after plastic deformation but also restrains nucleation of the precipitates of secondary α-phase in further stages of thermomechanical processing. It was established that developed phase morphology of the alloy determined its hot plasticity – especially in the range of low strain rates typical for superplastic deformation.

• Periodical: Materials Science Forum (Volumes 838-839)
• Pages: 143-149
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.838-839.143
• Online since: January 2016
• Authors: Maciej Motyka*, Jan Sieniawski
• Keywords: Fine-Structure Superplasticity, Fragmentation of α-Grains, Microstructure, Spheroidization of α-Grains, THERMOMECHANICAL PROCESSING, Titanium Alloys

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