Fabricating TiNiCu Ternary Shape Memory Alloy by Directed Energy Deposition via Elemental Metal Powders

Yitao Chen,Xinchang Zhang,Frank Liou,Joseph W Newkirk,Mohammad Masud Parvez

doi:10.3390/app11114863

Yitao Chen, Xinchang Zhang + Show 3 more

Open Access

https://doi.org/10.3390/app11114863

Copy DOI

Abstract

In this paper, a TiNiCu shape memory alloy single-wall structure was fabricated by the directed energy deposition technique with a mixture of elemental Ti, Ni, and Cu powders following the atomic percentage of Ti50Ni45Cu5 to fully utilize the material flexibility of the additive manufacturing process to develop ternary shape memory alloys. The chemical composition, phase, and material properties at multiple locations along the build direction were studied, using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Vickers hardness testing, tensile testing, and differential scanning calorimetry. The location-dependent compositions of martensitic TiNi and austenitic TiNi phases, mechanical properties, and functional properties were investigated in detail. Variations were found in atomic compositions of Ti, Ni, and Cu elements along the build direction due to the complex interaction between elemental powders and laser processing. Good correlations were present among the chemical composition, phase constituent, hardness, and feature of phase transformation temperatures at various locations. The ultimate tensile strength of the as-deposited TiNiCu alloy is comparable with the previously reported additively manufactured TiNi binary alloys. By adding Cu, a much lower thermal hysteresis was achieved, which shows good feasibility of fabricating ternary TiNiCu shape memory alloys, using elemental powders in the directed energy deposition to adjust the thermal hysteresis.

Highlights

Additive manufacturing (AM) has become a novel and essential fabrication method.The layer-based additive feature makes AM more flexible in both geometry and materials [1]
The as-prepared cross-section of the TiNiCu deposition was analyzed by Helios scanning electron microscope (SEM) in both the element composition and phase distribution
Ti and Cu start with a composition higher than the as-mixed composition in the powder state and decrease gradually when the location rises

Summary

Introduction

Additive manufacturing (AM) has become a novel and essential fabrication method.The layer-based additive feature makes AM more flexible in both geometry and materials [1]. Among various DED-related techniques, laser and powders are commonly used energy sources and raw materials, respectively [2]. As the manufacturing techniques of metal powder is improving, various types of metallic materials and industrial alloys have been made into pre-alloyed powders and used in DED, including steels [3,4,5], Inconel [6,7,8], titanium alloys such as Ti-6Al-4V [9,10,11] and aluminum alloys [12,13]. Examples include mixing metallic alloy powders with hard ceramic powders, such as TiC, SiC, and WC [15,16,17,18], to gain high hardness and wear resistance, and blending various types of elemental metal powders to synthesize industrial alloys and novel alloys, such as functionally graded alloys

Methods

Results

Conclusion