Effect of Sintering Temperature on the Microstructure and Integrated Properties of MgAlTiVFeCo Lightweight High-Entropy Alloy

TL;DR

This study shows that sintering a lightweight high-entropy alloy at 1000°C gives it excellent hardness, oxidation resistance, and corrosion resistance.

Contribution

The paper identifies 1000°C as the optimal sintering temperature for achieving superior properties in MgAlTiVFeCo lightweight high-entropy alloys.

Findings

The alloy sintered at 1000°C achieved 96.7% densification and 1235.5 HV microhardness.

Oxidation rate constants at 1000°C were lower, showing better oxidation resistance.

Higher sintering temperatures improved corrosion resistance in NaCl solution.

Abstract

To develop and design new alloy materials with lightweight and superior comprehensive performance. In this study, a MgAlTiVFeCo lightweight high-entropy alloy (LW-HEA) was fabricated via mechanical alloying and spark plasma sintering (SPS) to investigate the effects of sintering temperature on its phase structure, microstructure, densification, microhardness, high-temperature oxidation resistance, and corrosion resistance. The results indicate that the ball-milled MgAlTiVFeCo LW-HEA formed a simple solid solution phase with a BCC structure. After spark plasma sintering, the phase structure of the alloy changed, maintaining the BCC phase as the primary phase while accompanying the precipitation of secondary phases. When the sintering temperature reached 1000 °C, the alloy achieved a densification of 96.7% and a microhardness of 1235.5 HV. Its hardness value is comparable to the typical range of cemented carbides, demonstrating outstanding mechanical properties. The oxidation kinetics of MgAlTiVFeCo high-entropy alloys sintered at different temperatures at 900 °C follow a parabolic law, which is diffusion-controlled and can be divided into two stages: rapid growth and slow stabilization. At a sintering temperature of 1000 °C, the fitted oxidation rate constants, kp1 (0–25 h) and kp2 (25–60 h), are 3.76 × 10−2 mg2·cm−4·s−1 and 1.10 × 10−1 mg2·cm−4·s−1, respectively, outperforming those of alloys sintered at other temperatures. In a 3.5 wt% NaCl solution, the corrosion resistance of the alloy improves with increasing sintering temperature. Compared to alloys sintered at medium-to-low temperatures (850–950 °C), the alloy sintered at a high temperature (1000 °C) exhibits a more positive corrosion potential (−0.438 V) and a lower corrosion current density (1.07 × 10−6 A·cm−2), indicating excellent corrosion resistance. It is evident that 1000 °C is the optimal sintering temperature, and the MgAlTiVFeCo LW-HEA demonstrates superior comprehensive properties.

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