Microstructural and texture evolution of Copper-(Chromium, Molybdenum, Tungsten) composites deformed by high-pressure-torsion

TL;DR

This study investigates how high-pressure torsion deforms copper-refractory metal composites, leading to ultrafine lamellar microstructures and specific fiber textures, with potential for advanced material applications.

Contribution

It demonstrates the formation of ultrafine lamellar structures in Cu-refractory metal composites through high-pressure torsion, revealing texture evolution and microstructural refinement.

Findings

Lamellar microstructure develops at high strains (~75).

Refractory metals form {hkl}<111> fiber textures.

Ultrafine lamellae (10-50 nm) can be retained with additional deformation.

Abstract

Cu-refractory metal composites containing Cr, Mo or W were subjected to severe plastic deformation using room temperature high-pressure torsion (HPT). A lamellar microstructure developed in each of the composites at equivalent strains of ~75. The refractory metals developed {hkl}<111> fibre textures with a slight tilt to the tangential direction. This texture was stronger and more clearly defined in Mo and W than in Cr. By applying additional HPT deformation to these samples, perpendicular to the original shear strain, it was found that the lamellar structure of Cu30Mo70 and Cu20W80 (wt.%) composites could be retained at high equivalent strains and the refractory layer thickness could be reduced to 20-50 nm in Cu20W80 and 10-20 nm in Cu30Mo70. Although neighbouring regions of the microstucture were aligned and there was evidence of local texture in both composites, the bulk texture of Cu30Mo70 became weaker during this second step of HPT deformation. This was attributed to the refractory metal lamellae being discontinuous and imperfectly aligned. This work shows that it is possible to form ultrafine composites of Cu-group VI refractory metals via high-pressure torsion, with namolamellar structures being possible where there is a sufficient volume fraction of Mo or W.