Compression behavior of bulk nanocrystalline Ni-Fe

Abstract

The mechanical behaviour of fully dense nanocrystalline Ni-19Fe (grain size 36-37 nm) was investigated by compression and deformation-trace observations with optical microscopy and atomic force microscopy in the temperature range from -162 to 600degreesC. The results indicated that yield stress (sigma(0.2)) increased with increasing strain rate with strain-rate sensitivity exponent m = 0.01 at ambient temperature, At the temperatures T < 100degreesC or T > 400degreesC yield strength decreased gradually with increasing temperature, while it dropped catastrophically in the range 100degreesC < T < 400degreesC. Low-temperature deformation produced two sets of macroscopic bandlike traces which oriented at around 55degrees to the compression axis and consisted of ultrafine straight lines