# Microstructure and Mechanical Properties of Nb35Zr26Ti19Hf15Mo5 Refractory High-Entropy Alloy Under Rolling and Heat Treatment

## TL;DR

This paper studies how rolling and heat treatment affect the structure and strength of a refractory high-entropy alloy used in high-temperature applications like aerospace.

## Contribution

The study reveals how cold rolling and heat treatment alter the microstructure and mechanical properties of a specific refractory high-entropy alloy.

## Key findings

- Cold rolling increases strength but reduces plasticity in the alloy.
- Annealing at 800 °C increases elongation to 17% and reduces dislocation density.
- Grain boundary changes during heat treatment weaken strengthening effects.

## Abstract

Refractory high-entropy alloys (RHEAs) have drawn much attention in the field of materials science for their unique properties and wide compositional design space. The Nb35Zr26Ti19Hf15Mo5 alloy is important for exploring RHEAs’ potential in high-temperature applications. It can break through existing material limitations and bring benefits to related fields, especially in the aerospace field. This paper focuses on Nb35Zr26Ti19Hf15Mo5 RHEAs and studies the effects of cold rolling and heat treatment on its microstructure and mechanical properties. The alloy has a single-phase BCC structure. As rolling reduction rises from 20% to 80%, the alloy’s strength increases notably while plasticity drops. At 80% rolling reduction, the tensile strength reaches 1408 MPa, and the elongation is 10.5%. During rolling, grains deform along the rolling direction, the number of low-angle grain boundaries grows, and dislocation and solid solution strengthening effects are enhanced. With the increase in annealing temperature, recrystallized grains increase, and the change in grain-boundary structure weakens the strengthening effect, leading to a strength decrease and a plasticity increase. After annealing at 800 °C, the elongation reaches 17%, and the dislocation density in the alloy decreases with a recrystallization degree of 49%.