Microstructure and Properties of Additively Manufactured AlCoCr0.75Cu0.5FeNi Multicomponent Alloy: Controlling Magnetic Properties by Laser Powder Bed Fusion via Spinodal Decomposition.

Xuan Yang,Roy Björkstrand,Mika Salmi,Yanling Ge,Oleg Heczko,Simo-Pekka Hannula,Joonas Lehtonen,Volker Uhlenwinkel

doi:10.3390/ma15051801

Abstract

A non-equiatomic AlCoCr0.75Cu0.5FeNi alloy has been identified as a potential high strength alloy, whose microstructure and consequently properties can be widely varied. In this research, the phase structure, hardness, and magnetic properties of AlCoCr0.75Cu0.5FeNi alloy fabricated by laser powder bed fusion (LPBF) are investigated. The results demonstrate that laser power, scanning speed, and volumetric energy density (VED) contribute to different aspects in the formation of microstructure thus introducing alterations in the properties. Despite the different input parameters studied, all the as-built specimens exhibit the body-centered cubic (BCC) phase structure, with the homogeneous elemental distribution at the micron scale. A microhardness of up to 604.6 ± 6.8 HV0.05 is achieved owing to the rapidly solidified microstructure. Soft magnetic behavior is determined in all as-printed samples. The saturation magnetization (Ms) is dependent on the degree of spinodal decomposition, i.e., the higher degree of decomposition into A2 and B2 structure results in a larger Ms. The results introduce the possibility to control the degree of spinodal decomposition and thus the degree of magnetization by altering the input parameters of the LPBF process. The disclosed application potentiality of LPBF could benefit the development of new functional materials.

Highlights

Two sets of process parameters have been employed, namely, the different volumetric energy density (VED) corresponding to the alteration of scanning speed under the same laser power, and the same VED referring to different laser power and scanning speed
The observations demonstrate that these three parameters contribute to the different aspects during the process, and they should all be optimized to achieve the best results
All laser powder bed fusion (LPBF) specimens are found to consist of body-centered cubic (BCC) phase, while the reference pulsed electric current sintered (PECS)

Summary

Introduction

The concept of mixing multiple principal elements, equiatomic, or nearequiatomic compositions, in one alloy system, and resulting in the high configurational entropy to promote the solid solution, was initially materialized by Cantor et al [6] and Yeh et al [7]. Among varieties of HEA systems, Alx CoCrCuFeNi (x = 0–3, in molar ratio) has been studied by Yeh et al [7] as an example that only simple solid solution structures form in HEAs, instead of the mixture of complicated phases produced in conventional alloys containing multiple principal elements. It has been confirmed that the Alx CoCrCuFeNi alloy consists of a single face-centered cubic (FCC) structure when the aluminum content x was in the range of 0 to 0.5 (equivalent to 0 to 9.09 at%), while a combination of FCC and body-centered cubic (BCC) structure was formed at x = 0.8. To form a single-phase structure using conventional methods, the Al content needs to be kept either quite low

Methods

Results

Discussion

Conclusion