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Microstructure and properties of functionally graded materials Ti6Al4V/TiC fabricated by direct laser deposition

Jingwei Zhang (Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA)
Yunlu Zhang (Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA)
Wei Li (Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA)
Sreekar Karnati (Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA)
Frank Liou (Department of Mechanical Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA)
Joseph W. Newkirk (Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 14 May 2018

840

Abstract

Purpose

This paper aims to manufacture Ti6Al4V/TiC functionally graded material (FGM) by direct laser deposition (DLD) using Ti6Al4V and TiC powder. The objective is to investigate the effect of process parameters and TiC composition on microstructure, Vickers hardness and mechanical properties.

Design/methodology/approach

Powder blends with three different volume percentages of Ti6Al4V and TiC were used as feed material for DLD process. Five experiments with different values of laser power and scan speed were conducted to investigate the effect on microstructure and Vickers hardness for different compositions of feed material. Mini-tensile tests were performed to evaluate the mechanical properties of the FGM samples. Digital image correlation (DIC) was applied to estimate Young’s modulus and ultimate tensile stress (UTS) of heterogeneous material.

Findings

This paper indicates that primary carbide, eutectic carbide and un-melted carbide phases are formed in the FGM deposit. As the energy density was increased, the primary and secondary dendrite arm spacing was found to increase. As TiC composition was increased, Young’s modulus increased and UTS decreased. The dendritic morphology of primary TiC growth was expected to cause low resistance for crack propagation, causing lower UTS values. Tensile specimens cut in vertical orientation were observed to possess higher values of Young’s modulus in comparison with specimens cut horizontally at low carbon content.

Originality/value

Current work presents unique and original contributions from the study of miniature FGM tensile specimens using DIC method. It investigates the effect of specimen orientation and TiC content on Young’s modulus and UTS. The relationship between energy density and dendritic arm spacing was evaluated. The relationship between laser power and scan speed with microstructure and Vickers hardness was investigated.

Keywords

Acknowledgements

This work was funded through NASA’s EPSCoR Grant #NNX13AM99A. The authors appreciate the NASA support.

Citation

Zhang, J., Zhang, Y., Li, W., Karnati, S., Liou, F. and Newkirk, J.W. (2018), "Microstructure and properties of functionally graded materials Ti6Al4V/TiC fabricated by direct laser deposition", Rapid Prototyping Journal, Vol. 24 No. 4, pp. 677-687. https://doi.org/10.1108/RPJ-12-2016-0215

Publisher

:

Emerald Publishing Limited

Copyright © 2018, Emerald Publishing Limited

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