Efficient Coarse-Grained Superplasticity of a Gigapascal Lightweight Refractory Medium Entropy Alloy

Area of Science:

• Materials Science
• Metallurgy
• Mechanical Engineering

Background:

• Superplastic metals offer exceptional ductility (>300%) for complex engineering components.
• Current superplastic alloys are limited by poor strength, long deformation times, and costly grain refinement.

Purpose of the Study:

• To address limitations of current superplastic alloys by developing a high-strength, coarse-grained superplastic material.
• To investigate the deformation mechanisms in a novel medium entropy alloy for enhanced superplastic forming.

Main Methods:

• Development of a coarse-grained superplasticity in a high-strength lightweight medium entropy alloy (Ti43.3V28Zr14Nb14Mo0.7).
• Microstructural analysis of ultrafine particles within a body-centered-cubic matrix.
• Characterization of superplastic deformation at 1173 K and a strain rate of 10^-2 s^-1.

Main Results:

• Achieved coarse-grained superplasticity exceeding 440% at a high strain rate (10^-2 s^-1) and elevated temperature (1173 K).
• The alloy demonstrated gigapascal residual strength, overcoming the typical trade-off with ductility.
• Identified a unique deformation mechanism involving dislocation slip, dynamic recrystallization, and grain boundary sliding.

Conclusions:

• The developed alloy offers a pathway for highly efficient superplastic forming of high-strength components.
• Broadens the application of superplastic materials into the high-strength engineering field.
• Provides guidance for the development of new advanced superplastic alloys.