Effect of Heat Treatment on the Microstructure and Mechanical Properties of Selective Laser-Melted Ti64 and Ti-5Al-5Mo-5V-1Cr-1Fe

Hongjie Bai,Xudong Cui,Dingguo Zhang,Xiaorong Qin,Tong Liu,Xianbo Liu,Longqing Chen,Hao Deng

doi:10.3390/met11040534

Abstract

Additive manufacturing (AM) has shown the ability in processing titanium alloys. However, due to the unique thermal history in AM, the microstructure of AM-fabricated parts is metastable and non-equilibrium. This work was aiming to tailor the microstructure and to improve the mechanical properties of α+β Ti-6Al-4V alloy and metastable β Ti-5Al-5Mo-5V-1Cr-1Fe alloys by manipulating the post-process heat treatment. The results showed that Ti-6Al-4V exhibited a metastable α’ martensite microstructure in the as-fabricated condition, while a metastable β structure was formed in as-printed Ti-5Al-5Mo-5V-1Cr-1Fe. After post-process heat treatment, both lamellar and bimodal microstructures were obtained in Ti64 and Ti-5Al-5Mo-5V-1Cr-1Fe alloys. Especially, the Ti-6Al-4V alloy subjected to 950 °C annealing showed the lamellar structure with the highest fracture toughness of 90.8 ± 2.1 MPa.m1/2. The one cyclically heat-treated has excellent combined strength, ductility and fracture toughness attributed to the bimodal structure. In addition, similar observations of lamellar and bimodal microstructure appeared in the post-process heat-treated Ti-5Al-5Mo-5V-1Cr-1Fe alloy. This study demonstrated that heat treatment is an effective way to tackle the non-equilibrium microstructure and improve the mechanical properties of selective laser melting (SLM)-fabricated titanium alloys.

Highlights

The versatility of Selective laser melting (SLM) has attracted significant interest in manufacturing high-value alloys used in aerospace, automobile and biomedical applications [2,3]
SLM-prepared Titanium alloys, columnar prior β grains are observed in the vertical side of both samples
In order to further investigate the detailed information about the side of order we to further investigate the detailed about the internalboth part samples

Summary

Introduction

Selective laser melting (SLM) is a promising rapid prototyping technology in producing metallic components and enabling freedom designs with a low material waste [1]. The versatility of SLM has attracted significant interest in manufacturing high-value alloys used in aerospace, automobile and biomedical applications [2,3]. A wide range of SLMfabricated alloys has been investigated, such as titanium alloys [4,5], aluminum alloys [6,7]. Titanium alloys, including both α+β Ti-alloys and metastable β Ti-alloys, have been processed by SLM. Similar to the welding process, SLM-fabricated Ti-alloys go through the repeated melting/solidifying process, in which the metallic powder is fused by a laser source layer by layer.

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Conclusion