Tensile Deformation of B19′ Martensite in Nanocrystalline NiTi Wires

Abstract Deformation mechanisms activated during tensile deformation of nanocrystalline NiTi wire in martensite state were investigated by combination two experimental methods: (i) analysis the evolution martensite-variant microstructures grains deformed TEM and (ii) texture situ synchrotron X-ray diffraction. The obtained results are linked to activity various twinning processes martensite. It is concluded that reorientation proceeds via motion interdomain interfaces, gives rise reoriented with microstructure consisting single (001) compound-twinned domain each grain sharp two-fiber process leaves behind only very small unrecovered strains few dislocation defects austenitic after unloading heating. Plastic B19′ peculiar mechanism which combines (100) [100]/(011) slip based kinking. special variant twin bands kink containing lattice aligned [010] direction characteristic texture. Reverse martensitic transformation plastically upon heating large high density austenite. But there also significant recoverable up 10%. While matrix transforms into parent austenite matrix, (20-1) twins transform {114} twins.