**The Relationship of Fracture Mechanism between High Temperature Tensile Mechanical Properties and Particle Erosion Resistance of Selective Laser Melting Ti-6Al-4V Alloy**

#### **Jun-Ren Zhao, Fei-Yi Hung \*, Truan-Sheng Lui and Yu-Lin Wu**

Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan; a2x346yz03@gmail.com (J.-R.Z.); luits@mail.ncku.edu.tw (T.-S.L.); nick22530682@hotmail.com (Y.-L.W.) **\*** Correspondence: fyhung@mail.ncku.edu.tw; Tel.: +886-6-275-7575 (ext. 62950)

Received: 22 March 2019; Accepted: 26 April 2019; Published: 29 April 2019

**Abstract:** In this study, selective laser melting (SLM) Ti-6Al-4V is subjected to heat treatment for 4 h at 400 ◦C, 600 ◦C, and 800 ◦C, followed by air cooling. After heat treatment at 400 ◦C and 600 ◦C, the ductility was lower (strength increased). This was could be for two reasons: (1) high temperature tensile properties, and (2) particle erosion wear induced phase transformation. Finally, the particle erosion rates of as-SLM Ti-6Al-4V and heat treatment for 4 h at 800 ◦C (labeled 800-AC) were investigated and compared; the lamellar α + β phases in 800-AC are difficult to destroy with erosion particles, resulting in the erosion resistance of 800-AC being higher than that of the martensitic α' needles in the as-SLM Ti-6Al-4V at all impact angles (even the hardness of the 800-AC specimen was lower). The as-SLM Ti-6Al-4V alloy needs heat treatment to have better wear resistance.

**Keywords:** selective laser melting (SLM); Ti alloy; high temperature tensile; erosion; wear
