Surface modification of titanium nickelide after bombardment by silicon ions

Abstract

The changes in the microstructure of the surface layers in titanium nickelide after bombardment by moderate-energy silicon-ion fluxes are studied by electron backscatter diffraction. After bombardment, the structure of the TiNi surface is modified, with reduction in grain size. The layer with fragmented structure is characterized by the presence of martensite phase B19′; high concentration of interphase and intraphase boundaries; and fragments smaller than 1 μm. The decrease in grain size at the irradiated surface layer is nonuniform and depends on the crystallographic orientation of the initial grain. (The internal structure is fragmented over almost a third of an individual grain. In the adjacent grain, no marked structural changes are seen.) The fragmentation is most pronounced in grains whose crystallographic orientation relative to the direction of action is close to 〈111〉. The angular disorientation of the fragments relative to the initial crystallographic orientation of the B2 structure is analyzed.