Achieving Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nb Alloys with High Strength and Moderate Ductility through Selective Laser Melting.

Jiangtao Ran,Xiaojing Sun,Zhuo Chen,Hong Zhao,Shiliang Wei

doi:10.3390/ma13235527

Abstract

Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nb (TA32) titanium alloy is a kind of near α high temperature titanium alloy with great application prospects in aero-engine afterburners and cruise missiles. However, there are still few studies on the microstructure and mechanical properties of TA32 specimens produced by selective laser melting (SLM) technology. In this study, TA32 specimens with high strength (tensile strength of 1267 MPa) and moderate ductility (elongation after fracture of 8%) were obtained by selective laser melting. The effect of laser power on the microstructure and mechanical behavior was studied and the results demonstrated that the average grain size increases with increasing laser power from 200 W to 400 W. Micro-zone composition analysis was carried out by energy dispersion spectrum (EDS), showing that the Al concentration inner grains is higher than that near grain boundaries. Fracture analysis results demonstrated that the fracture mode of SLM TA32 specimens was cleavage fracture. The tensile strength of the specimens built with a laser power of 250 W at 500 °C, 550 °C and 600 °C was measured as 869 MPa, 819 MPa and 712 MPa, respectively.

Highlights

Additive manufacturing of titanium alloys has attracted an increasing amount of attention because there is still a big challenge for the fabrication of titanium alloy parts with traditional methods, especially when complex geometries are taken into consideration
Before this experiment was carried out, a series of small cubic TA32 specimens (12 mm × 12 mm × 12 mm) with different process parameters were built by selective laser melting to investigate the influence of process parameters on the porosity and Vickers hardness of SLM TA32 specimens, and the results showed that laser power had the greatest influence on the porosity and Vickers hardness
The diffraction peaks of all samples have the characteristics of hexagonal close packed (HCP) phase, which is composed of α phase and α’ martensite phase

Summary

Introduction

Additive manufacturing of titanium alloys has attracted an increasing amount of attention because there is still a big challenge for the fabrication of titanium alloy parts with traditional methods, especially when complex geometries are taken into consideration. Fine acicular α’ martensite was found to exist in the as-built SLM TC4 alloys due to the extremely high cooling rate [6,7,8,9,10,11,12,13]. The width of these acicular α0 needles varied from microns in the case of primary α0 down to nanometers for quaternary α0 [7]. These α0 needles can be categorized into four subgroups: primary martensite phase, secondary martensite phase, tertiary martensite phase and quaternary martensite

Methods

Results

Conclusion