Controlling the tensile and fatigue properties of selective laser melted Ti-6Al-4V alloy by post treatment

The microstructure, phase composition, tensile and fatigue properties of Ti-6Al-4V samples produced by selective laser melting (SLM), SLM followed by heat treatment (HT), and SLM followed by hot isostatic pressing (HIP) were investigated to explore a simpler approach to improve the mechanical performances by post treatment at minimum cost in our work. Results showed that the tensile and fatigue properties of the as-SLMed samples were far below the level of wrought counterpart. Heat treatment and HIP can more obviously enhance tensile properties and fatigue performances, respectively. The microstructure consisted of the lamellar or acicular a and grain boundary alpha within prior beta columnar grain boundaries in the SLMed samples after solution treatment at 850 degrees C followed by water quenching, whose tensile properties were improved to be 1085 MPa, 859 MPa, 14.0%. A tri-modal microstructure including lamellar alpha, polygonal alpha and acicular nanoscale alpha+beta phase formed in the samples after 850 degrees C solution treatment and 550 degrees C aging treatment. Their corresponding tensile properties were enhanced to be 1192 MPa, 1054 MPa, 11.4%. The microstructure was composed of lamellar alpha+beta phases for the SLMed sample after HIP treatment, which improved the tensile (>1000 MPa, >850 MPa, and >10%) and fatigue (10(5-6) at the stress amplitude of 500 MPa) properties. Therefore, solution treatment at 850 degrees C followed by water quenching or HIP treatment is a simpler method to control the performances of the SLMed Ti-6Al-4V alloy. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Heat treatment at 850 degrees C followed by water quenching or HIP treatment can significantly enhance the tensile and fatigue properties of SLMed Ti-6Al-4V alloy, forming a tri-modal microstructure to further improve the material performance.