The Microstructure Transformation and Mechanical Properties in Selective Laser Melting Processed Ti-6Al-4V at Different Heights

Abstract

The present work indicated that both the microstructure morphology and occupation of the selective laser melting processed Ti-6Al-4V exhibited regular transformation as the sampling height varied. In turn, the mechanical performance changed accordingly. Due to the great temperature gradient, the microstructure mainly consisted of martensite α′. Additionally, as the sampling heights increased, the microstructure transformed as the following rule: coarse lamellar α′—fine articular α′—ultrafine Z-zigzag α′. Close examination indicated that the martensite phase can be further distinguished into primary α′, secondary α ′, tertiary α′ and quartic α′ based on the size and the generating location. With the sampling height increased, both the size and volume occupation of tertiary and quartic α′ decreased. The generation and transformation of the tertiary α′ and quartic α′ were significantly affected by the thermal cycle intensity and times. Correspondingly, the tensile strength increased slightly as the sampling height increased.