Design and Fabrication of New High Entropy Alloys for Evaluating Titanium Replacements in Additive Manufacturing.

Prashant Sarswat,Sayan Sarkar,Taylor Smith,Michael Free,Arun Murali

doi:10.3390/ma13133001

Abstract

High entropy alloys (HEAs) were prepared using the powder bed fusion (PBF) technique. Among titanium free alloys AlCoCrFeNiMn, CoCr1.3FeMnNi0.7, AlCoCrFeNi1.3, and AlCoCr1.3FeNi1.3 have been further investigated. A cost comparison was done for these four alloys as well as the titanium-based alloys AlCoCrFeNiTi and AlCo0.8CrFeNiTi. Such a comparison was done in order to evaluate the performance of the titanium-free alloys as the estimated cost of these will be less than for Ti-based HEAs. Hence, we have chosen four titanium free alloys and two titanium-based alloys for further processing. All these alloys were fabricated and subsequently characterized for phase, purity and performance. Scanning electron microscopy-based images were captured for microstructure characterization. EIS-based tests and potentiodynamic scans were performed to evaluate corrosion current. Hardness tests were performed for mechanical properties evaluation. Additional testing using factorial design tests was performed to evaluate the effects of various parameters to create better PBF-based HEA samples. EBSD tests, accelerated corrosion tests (mass loss), chemical analysis after degradation, microstructure analysis before and after degradation, and mechanical property comparison for finalized samples and other similar tests were executed. The details about all these HEAs and subsequent laser processing as well as behavior of these HEAs have been included in this study. It has been observed that some of the selected alloys exhibit good performance compared to Ti-based alloys, especially with respect to improvements in elastic constant and hardness relative to commercially pure Ti.

Highlights

High entropy alloy fabrication generally utilizes multiple metallic elements in near-equiatomic ratios [1]
The assumption that cost of labor, laser melting, post deposition sample cleaning are similar for each High entropy alloys (HEAs), for the present case, the deciding factor for cost will be the cost of the constituent metallic powders
It was observed that Ni addition increases the driving force to form BCC_B2 phase of AlCoCrFeNi as the content of Ni is increased at temperatures below 1000 ◦ C, at temperatures over 1000 ◦ C, increasing Ni addition has negligible effect on the driving force required to form the B2_BCC phase

Summary

Introduction

High entropy alloy fabrication generally utilizes multiple metallic elements in near-equiatomic ratios [1]. The random solid solution of a specific high entropy combination (HEA) has a subjective (arbitrary) distribution of the elements situated along lattice points [1]. Extraordinary properties (such as high ductility and fracture toughness, specific strength, and better mechanical performance at elevated temperature) have been exhibited by various HEAs, which enable their use and expand their potential for a variety of present and anticipated future applications. Seven general families of HEAs (CCAs) have been reported. HEAs are primarily alloys with disordered solid solutions. Solid solution reinforcement is more pronounced for single-phase HEAs than for standard alloy systems (such as stainless steels, bronze, brass, 3xxx, 5xxx, and alpha Ti alloy) [1,2]

Methods

Results

Conclusion