Effect of HfO2 Nanoparticles on the Shape and Parameters of Pseudoelastic Stress–Strain Curves of Cu–Al–Ni Alloy Single Crystals

Abstract

The effect of hafnium dioxide (HfO₂) disperse nanoparticles on the shape and parameters of stress–strain curves for the compression of Cu–13.5 wt %Al–4.0 wt %Ni alloy single crystals with memory effect has been investigated. It is found that 30-nm nanoparticles with a volume fraction of 1% affect the shape of pseudoelastic stress–strain curves of an alloy crystal, namely, substantially elevate its (martensite) strain-hardening coefficient θ and deformation work and eliminate deforming stress drops associated with the existence of interfacial stresses under martensite transformation, but do not affect the hysteresis of pseudoelastic stress–strain curves and deformation of shape memory. Simulation of pseudoelastic stress–strain curves and analysis of results using the smeared martensite transformation have revealed that the increase in coefficient θ ~ ω^–1 and elimination of stress drops on pseudoelastic stress–strain curves are associated with a considerable (order-of-magnitude) decrease in martensite nucleus volume ω ~ w, where w is the transverse size of nanoparticles.