Microstructural evolution of a Ti-6Al-4V alloy during thermomechanical processing

Variation of microstructure of a Ti-6Al-4V alloy during thermo mechanical processing at a range of hot working conditions (temperature: 850-1050 degreesC, strain rate: 0-1.0 s(-1) has been investigated for further understanding and control of the processing-structure-property relationships. The influences of hot working parameters on deformation localization, width of alpha platelets, (alpha --> beta) phase transformation, and (meta)dynamic recrystallization were systematically examined by optical microscopy and scanning electron microscopy. The experimental results showed that the lamellar morphology of the alpha phase can be sub-divided into five different categories for samples processed in the (alpha + beta) phase field, and these represent three stages of the (alpha --> beta) phase transformation. It was also noted that a certain degree of the (alpha --> beta) phase transformation occurred concurrently with the mechanical deformation in the (alpha + beta) phase field. The experimental evidence suggests that dynamic and/or metadynamic recrystallization has occurred in the beta phase field, but was not involved in the (alpha + beta) phase field under the experimental conditions. (C) 2002 Elsevier Science B.V. All rights reserved.