Pseudoelastic Deformation of CuAlMn Single Crystals

Abstract
Martensitic transformation associated with a tensile deformation of CuAlMn single crystals in [100] direction was studied using in-situ transmission electron microscopy. Stress/strain curves obtained during pseudoelastic deformation of microscopic samples were slightly different from bulk ones due to martensite formation in the stage of stress increase and a permanent deformation during the first cycle. Individual needles of 2H martensite were formed already in the early deformation stage. They were growing during stress increase, joining together into large plates. At later deformation stages 18R martensite was formed usualy in stacks of single plates. Following crystallographic relationship between parent and martensitic phases was observed : [001]β₁||[010]γ',β'and[110]β₁||[001]γ',β'. At a high stress concentration near crack tips, α' martensite of 3R lattice was observed. Identification of martensite structure was very often not possible there, due to an extremely high random stacking faults density.