Auger electron spectroscopy of high-speed-deformed Ni/Cu layers

Ni/Cu double- and multilayers subjected to high-speed deformation were investigated by Auger electron spectroscopy (AES) using depth profiling. Ni and Cu thin films were alternately deposited on a 0.3 mm thick Ni substrate using RF magnetron sputtering. The thickness of the double-layer was 90 nm, while that of the multilayer was 160 nm. High-speed compression was performed using bullet masses from 30.0 to 57.4 g at varying bullet speeds between 16.8 and 48.5 m s⁻¹. The strain rate ranged from 6.7×10⁴ to 8.4×10⁵ s⁻¹. Upon high-speed deformation, the thickness of the Ni/Cu double-layer was reduced to about 80% of its original value. The Cu thin film was compressed to a greater extent relative to the Ni thin film (by about 15%), which may be due to the difference in malleability between the two metals. At a strain rate of 8.4×10⁵ s⁻¹, the Ni/Cu double-layer virtually disappeared. Ni/Cu interdiffusion was enhanced by high-speed deformation. The degree of interdiffusion appeared to be greater at lower strain rates. Cu_0.5Ni_0.5 and Cu_0.75Ni_0.25 thin film alloys formed in the high-speed-deformed multilayer sample, indicating that high-speed compression could potentially be used to prepare thin film metal alloys.