Effect of microstructure on Ti3Al precipitation during ageing of Ti-6Al-4V alloy

Bruna Callegari ,J V Marçola,F Mücklich ,Katherine Aristizábal ,F Soldera ,Haroldo Cavalcanti Pinto

doi:10.1051/matecconf/202032112014

Bruna Callegari , J V Marçola + Show 4 more

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https://doi.org/10.1051/matecconf/202032112014

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Abstract

The aim of the present work is to explore the age-hardening potential of Ti-6Al-4V (Ti-64) alloy with variation of the starting microstructure, with attention to the precipitation of nano-sized Ti3Al phase, as influenced by microstructural features. The alloy was either solution-treated or deformed by compression at temperatures above and below its β-transus to produce microstructures comprising martensitic, lamellar and globular α morphologies, as well as the existence or absence of β phase, and subsequently submitted to ageing treatments at 400°C/8h using in situ x-ray diffraction. Precipitated fractions of Ti3Al were obtained via Rietveld refinement and aged microstructures were characterized by micro-hardness measurements. Results show that α2 precipitation is favored by a globular morphology of α and hindered by a martensitic α morphology, and suggest that the presence of β phase also has as influence on precipitation.

Highlights

Ti-6Al-4V is the main representa ve of α+β alloys, responsible for more than 50% of all tanium alloys’ applica ons
Previous works on Ti-6Al-4V alloy have demonstrated that the driving force for α2 forma on depends on Al concentra on in α phase, and on oxygen concentra on
The microstructure is formed by coarse equiaxed prior β grains, with sizes in the order of 500 μm, within which α presents itself precipitated with a sharp martensi c morphology in the case of 1050HT condi on and with an intermediate lamellar morphology in 700HT (Figure 2b)

Summary

Introduction

Ti-6Al-4V (composi on in wt%) is the main representa ve of α+β alloys, responsible for more than 50% of all tanium alloys’ applica ons. As an ordered intermetallic phase, Ti3Al-based systems present a combina on of lightness and high temperature strength, despite its limited room-temperature duc lity and toughness, which makes them interes ng for the aerospace industry [9]. Within this context, the present work is presented, with the objec ve of studying the ageing behavior of Ti-64 alloy, focused on the precipita on of α2 phase, with varia on of the ini al microstructure by a combina on of heat treatments and thermomechanical processing. Its β-transus temperature, obtained via differen al scanning calorimetry, was approximately 995°C

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