Effect of energy density on quasi-static and dynamic mechanical properties of Ti-6Al-4V alloy additive-manufactured by selective laser melting

A selective laser melting (SLM) technique, which employs a high laser power as its heat source, was used to additively manufacture a Ti-6Al-4V alloy effectively. SLM process can inevitably cause various defects in the products due to the rapid melting and solidification of metal powder. The key factors that affect the dynamic properties of additive manufacturing products using titanium powders may differ from the factors that affect quasi-static properties. This study aimed to control defects such as pores, unmelted powders, and lack of fusion by changing the energy density among the SLM process conditions. The changes in texture and volume fraction of the irregular and regular regions were analyzed according to the energy density. The acicular alpha ' martensite fraction increased as the energy density increased, and the quasi-static mechanical properties could be improved by forming Widmanstatten microstructure with relatively random orientations after an additional hot isostatic pressing treatment. The SLM-fabricated Ti-6Al-4V alloy showed very high cycle fatigue strength (714 MPa), which was an excellent dynamic fatigue property compared to the existing wrought Ti-6Al-4V alloy, by improving resistance to fatigue crack propagation by irregularly oriented microstructure.

Automated summary

This study used a high laser power as the heat source in a selective laser melting (SLM) technique to effectively additive manufacture a Ti-6Al-4V alloy. By changing the energy density among the SLM process conditions, the study aimed to control defects and improve the quasi-static mechanical properties. The results showed that increasing the energy density led to an increase in the acicular alpha ' martensite fraction and improved quasi-static mechanical properties.