Structural relaxation and crystallization of NiTi thin film metallic glasses

This letter demonstrates the effects of structural relaxation on the crystallization and phase transformation behavior of NiTi thin films. Heat treatments below the glass transformation temperature produce films with a greater hardness than as-deposited films. The reduction in free volume occurring during film relaxation plays a role. Using scanning electron microscopy, structural relaxation was found to decrease the overall crystallization time and increase the nucleation rate, thus modifying the resulting microstructures. Structural relaxation had little effect on the phase transformation temperatures of fully crystallized films, but slightly increased the resulting actuation force during transformation. (C) 2009 American Institute of Physics. [doi:10.1063/1.3236544]