Crystallographic Characterization of Dual Phase Transformations in Shape Memory Alloys
Paper ID : 1277-ICNS (R1)
Firat University, Department of Physics
Some alloys exhibit a peculiar property called shape memory effect, which is based on successive dual thermal and stress induced martensitic transformations. Thermal induced transformation occurs along with lattice twinning on cooling and ordered parent phase structures turn into twinned martensite structures, these twinned structures turn into detwinned martensite structure by means of stress induced transformation by deforming plastically in martensitic condition. Thermal induced transformation occurs cooperative movement of atoms in two opposite directions, <110 > -type directions on the {110}-type planes of parent austenite structure. Copper based alloys exhibit this property in metastable β-phase region. Lattice invariant shears are not uniform in these alloys, and the ordered parent phase structures martensitically undergo the non-conventional layered structures on cooling. In the present contribution, x-ray and electron diffraction studies were carried out on two copper based CuZnAl and CuAlMn alloys. These alloy samples have been heat treated for homogenization in the β-phase fields. X-ray diffraction profiles and electron diffraction patterns exhibit super lattice reflections. X-ray diffractograms taken in a long time interval show that diffraction angles and intensities of diffraction peaks change with the aging time at room temperature, and this result leads to the rearrangement of atoms in diffusive manner.
Shape memory effect, martensitic transformations, lattice twinning and detwinning.
Status : Abstract Accepted (Poster Presentation)