Microstructure and Properties of Functionally Graded Materials Ti6Al4V/TiC Fabricated by Direct Laser Deposition

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.

Department(s)

Mechanical and Aerospace Engineering

Second Department

Materials Science and Engineering

Research Center/Lab(s)

Intelligent Systems Center

Comments

This work was funded through NASA's EPSCoR Grant #NNX13AM99A.

Keywords and Phrases

Digital image correlation; Direct laser deposition; Functionally graded material; Mechanical properties; Microstructure; Ti6Al4V/TiC

International Standard Serial Number (ISSN)

1355-2546

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2018 Emerald Group Publishing Ltd., All rights reserved.

Publication Date

01 May 2018

Link to Full Text

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