Microstructure, defects and mechanical behavior of beta-type titanium porous structures manufactured by electron beam melting and selective laser melting

Document Type

Journal Article

Publication Title

Acta Materialia

Publisher

Elsevier

School

School of Engineering

RAS ID

21216

Comments

Liu, Y. J., Li, S. J., Wang, H. L., Hou, W. T., Hao, Y. L., Yang, R., . . . Zhang, L. C. (2016). Microstructure, defects and mechanical behavior of beta-type titanium porous structures manufactured by electron beam melting and selective laser melting. Acta Materialia, 113, 56-67. Available here

Abstract

This study investigates the differences in the microstructure, defects and mechanical behavior of porous structures from a β-type Ti24Nb4Zr8Sn manufactured by electron beam melting (EBM) and selective laser melting (SLM). The phases, size and shape of melt pool, volume and distribution of defects are analyzed and correlated to the compressive mechanical and fatigue properties. Due to different powder bed temperatures, the microstructure of EBM and SLM samples consists of α+β phases and a single β phase, respectively. The faster cooling rate during SLM promotes the formation of fine β dendrites, which leads to a higher compressive strength (50 ± 0.9 MPa) and lower Young's Modulus (0.95 ± 0.05 GPa) in comparison to the EBM parts (45 ± 1.1 MPa and 1.34 ± 0.04 GPa respectively). The large defects present within solid strut are likely a result of tin vaporization. The tin vapor is more easily trapped during the SLM process due to a smaller laser spot size and a faster cooling rate. This results in a 10 times increase in the number of defects. These defects have a limited influence on both the static properties and low stresses level fatigue strength, but it causes a reduced and variable fatigue life at high stresses level.

DOI

10.1016/j.actamat.2016.04.029

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