AMORPHIZATION OF NiZr INTERFACES UNDER CONTROLLED CONDITIONS OF DEFORMATION AND TEMPERATURE

Overview & Synopsis

We propose a novel method of mechanically deforming a bulk diffusion couple which allows to separate the effects of plastic deformation on the reaction kinetics from the concurrent thermal effects. Trilayer specimens prepared placing a Ni foil between two Zr sheets and having an area of about 25 mm2 were subjected to a load normal to the interfaces of up to 220 KN applied in about 0.1 s. The effective interface temperature during this process, which was found to be of the order of 100 C, was measured on the sample itself using the NiZr interface as the hot junction of a NiZr thermocouple and checked on a dummy sample using a very thin NiCr-NiAl thermocouple. Cross sectional specimens for TEM were prepared by Ar ion beam milling on a liquid N2 cooled stage. First results show the presence of an amorphous layer at the Ni-Zr interface whose thickness depends on the amount of plastic deformation. Comparison with the growth rates of amorphous NiZr derived from isothermal annealing shows that the mechanical deformation strongly enhances the interdiffusion process.