Microstructure and Failure Characteristics of Nanostructured Molybdenum Copper Composites

TL;DR

This study investigates how severe plastic deformation transforms CuMo composites into nanostructured lamellar materials, significantly enhancing their strength and hardness while examining their anisotropic fracture toughness.

Contribution

It demonstrates the microstructural evolution and mechanical property improvements in CuMo composites subjected to high pressure torsion, highlighting anisotropic damage tolerance.

Findings

Lamellar structures form with nanometer-scale layers.

Strength and hardness increase substantially with deformation.

Fracture toughness becomes anisotropic due to lamellar alignment.

Abstract

Liquid-metal infiltrated Cu30Mo70 (weigth percentage) is subjected to severe plastic deformation using high pressure torsion. The initially equiaxed dual phase structure is gradually transformed into a lamellar structure composed of individual Cu and Mo layers. The thickness of the lamellae varies between the micrometer and nanometer ranges depending on the amount of applied strain. Consistent with the refinement of the microstructural features, strength and hardness substantially increase. In addition, an acceptable ductility is found in the intermediate deformation range. An assessment of the damage tolerance of the produced composites is performed by measuring the fracture toughness in different crack propagation directions. The results indicate the development of a pronounced anisotropy with increasing degree of deformation which is an effect of the concurrent alignment of the nanostructured lamellar composite into the shear plane.