Evolution of a martensitic structure in a Cu–Al alloy during processing by high-pressure torsion

A Cu-11.8 wt% Al alloy was quenched in iced water from a high temperature (850 °C) to introduce a martensitic phase and then the alloy was processed using quasi-constrained high-pressure torsion (HPT). The micro-hardness and the microstructures of the unprocessed and severely deformed materials were investigated using a wide range of experimental techniques (X-ray diffraction, optical microscopy, scanning electron microscopy, transmission electron microscopy, and high- resolution TEM). During HPT, a stress-induced martensite–martensite transformation occurs and an \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \alpha^{\prime}_{1} $$\end{document} martensite phase is formed. In the deformed material, there are nanoscale deformation bands having high densities of defects and twins in the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \alpha^{\prime}_{1} $$\end{document} martensite. It was observed that a high density of dislocations became pinned and accumulated in the vicinity of twin boundaries, thereby demonstrating a strong interaction between twin boundaries and dislocations during the HPT process.