Abstract
In this work, the design, microstructures and mechanical properties of five novel non-equiatomic lightweight medium entropy alloys were studied. The manufactured alloys were based on the Al65Cu5Mg5Si15Zn5X5 and Al70Cu5Mg5Si10Zn5X5 systems. The formation and presence of phases and microstructures were studied by introducing Fe, Ni, Cr, Mn and Zr. The feasibility of CALPHAD method for the design of new alloys was studied, demonstrating to be a good approach in the design of medium entropy alloys, due to accurate prediction of the phases, which were validated via X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. In addition, the alloys were manufactured using an industrial-scale die-casting process to make the alloys viable as engineering materials. In terms of mechanical properties, the alloys exhibited moderate plastic deformation and very high compressive strength up to 644 MPa. Finally, the reported microhardness value was in the range of 200 HV0.1 to 264 HV0.1, which was two to three times higher than those of commercial Al alloys.
Highlights
To overcome the above concerns, High Entropy Alloys (HEAs) and equiatomic multicomponent alloys were proposed respectively by Yeh et al.[2] and Cantor et al.[3] in 2004
Following the previously mentioned new route to design non-equiatomic Medium Entropy Alloys (MEAs), the range of matrix composition was defined between 65 at.% and 70 at.%
From above mentioned classification based on the ranges of ∆Sconf, alloys can be divided in low, medium and high entropy alloys
Summary
To overcome the above concerns, High Entropy Alloys (HEAs) and equiatomic multicomponent alloys were proposed respectively by Yeh et al.[2] and Cantor et al.[3] in 2004. Alloys were classified as Medium Entropy Alloys (MEAs), when the values of their ΔSconf were in the range from 1R to 1.5 R. Inspired by HEAs, Raabe et al developed novel steels based on high ΔSconf for stabilizing a single-phase SS matrix[12]. Excellent mechanical properties were often obtained on compression and hardness tests for studied LWMEAs. Mg46(MnAlZnCu)[54] and Mg50(MnAlZnCu)[50] alloys exhibited moderate hardness (178 HV-226 HV) and high compression strength (400 MPa–482 MPa) at RT, but they exhibited a brittle behaviour[29]. AlLiMgZnSn and AlLi0.5MgZn0.5Sn0.2 alloys exhibited very brittle behaviour, with plastic strain values below 1,2% In another related study, Beak et al reported the microstructure and compressive properties of Al70Mg10Si10Cu5Zn5 alloy at RT and 350 °C. The fabricated alloys had high strength, with compressive strength exceeding 500 MPa at RT
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