Development of a Recyclable High-Entropy Alloy for Lightweight Automotive Applications: Processing, Microstructure, and Mechanical Performance

Project Abstract

This study presents the design, synthesis, and comprehensive evaluation of a recyclable high-entropy alloy (HEA) tailored for lightweight automotive applications, focusing on processing routes, microstructural evolution, and mechanical performance under service-relevant conditions. The work addresses the dual objectives of achieving superior strength-to-weight ratios and enabling closed-loop recyclability to reduce lifecycle environmental impact. An equiatomic or near-equiatomic multi-element system incorporating light, transition, and refractory elements was selected to balance solid-solution strengthening with controlled precipitation and phase stability. Powder metallurgy and arc-melting followed by vacuum arc remelting and hot isostatic pressing were employed to produce dense, homogeneous HEA billets, with emphasis on scalable processing compatible with automotive manufacturing. Comprehensive phase analysis using X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy revealed a predominantly face-centered cubic (FCC) or mixed FCC/BCC phase constitution with fine, dispersoid-rich grains that promote high yield strength via solid-solution strengthening and grain-boundary strengthening mechanisms. Thermomechanical treatments, including solution annealing and controlled aging, were optimized to tailor precipitate morphology, coherency, and distribution, thereby achieving a favorable combination of tensile strength, ductility, and fracture resistance. Mechanical performance assessment encompassed uniaxial monotonic loading, strain hardening behavior, low- and high-cycle fatigue, and impact toughness at room and elevated temperatures to simulate real-world automotive service. Notably, the alloy demonstrated a high specific strength and good ductility with a notable work-hardening rate, contributing to crashworthiness and energy absorption requirements. Elevated-temperature performance indicated retention of strength with acceptable ductility up to 300–500 °C, aligning with engine bay and under-hood environments. Corrosion resistance in representative automotive media (neutral salt spray and acidic environments) was evaluated to ensure environmental durability during service, and recyclability tests confirmed minimal phase decomposition and compositional loss after multiple remelting cycles, supporting closed-loop material reuse. A multi-criteria optimization framework integrated processing parameters, microstructural descriptors, and mechanical outcomes to map processing–structure–property relationships and identify robust processing windows for scalable production. Life-cycle assessment highlighted reductions in embodied energy and greenhouse gas emissions when compared with conventional high-strength steels and aluminum alloys, driven by lower density and recyclability advantages. The findings elucidate the mechanisms by which the HEA microstructure evolves under thermomechanical processing and how these changes govern macroscopic properties, enabling targeted design of HEAs for lightweight automotive components such as chassis rails, wheels, and structural panels. The study provides a validated, industry-relevant pathway for deploying recyclable HEAs in automotive manufacturing, contributing to performance gains without compromising sustainability or end-of-life recyclability.

Project Overview

What This Project Is About

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A plain-language overview of the topic and what the project investigates.

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The Problem It Addresses

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What problem or gap this project tackles and why it matters to the field or society.

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Objectives of the Project

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1. Understand what high-entropy alloys are and why recyclability is important.
2. Identify a suitable alloy system for lightweight automotive use.
3. Characterize how processing choices affect structure and properties.
4. Evaluate the balance between strength, ductility, and weight reduction.
5. Propose a recyclable processing pathway with minimal environmental impact.

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What You Will Do Step by Step

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1. Review basic concepts of alloys and recycling in simple terms.
2. Select alloy compositions and design experiments for processing routes.
3. Prepare samples using accessible fabrication methods (e.g., casting, simple heat treatments).
4. Test basic mechanical properties and observe microstructure with basic instruments.
5. Analyze data to link processing steps with performance outcomes.
6. Assess recyclability through simple life-cycle considerations.
7. Document findings and discuss practical implications for automotive applications.

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Expected Outcome

Clear understanding of how a recyclable high-entropy alloy can meet lightweight automotive needs, with a recommended processing approach and a plan to assess recyclability.