Effect of concentrated solar energy on microstructure evolution of selective  laser melted Ti-6Al-4V alloy.

This paper aims at analyzing the effect of heat treatment using Concentrated Solar Energy (CSE) on the martensitic microstructure evolution of Ti-6Al-4V alloy manufactured by Selective Laser Melting (SLM) technology. The application of CSE, a renewable energy sources, in post-processing of SLMed Ti-6Al-4V alloy is discussed based on heat treatments performed at Plataforma Solar de Almeria, Spain, using solar furnace SF40. In SLM process of Ti-6Al-4V powder because of local high heating followed by a rapid cooling the microstructure consists of an acicular martensite (α′ phase). Decomposition of α′ martensite of SLMed Ti-6Al-4V after heat treatment in solar furnace, using CSE, by SEM, EDX, TEM, SAED, and XRD analyses, was investigated. It has been found that for treatment below β-transus at 705 °C, because of low temperature, the α′ martensite was not fully converted into α + β and the β phase was not identified by XRD analysis. Heat treatments below (940 °C followed by 650 °C) and above (1050 °C) β-transus have revealed that α′ martensite was converted into a lamellar α + β mixture and also β phase was identified by XRD and TEM analysis. In the analyzed areas, middle areas of the samples contain an area fraction of β phase greater than the top areas. Area fraction of β phase, after heat treatment above β-transus, at 1050 °C, is greater than that obtained after treatment below β-transus. [ABSTRACT FROM AUTHOR]