Analysis of porosity in NiTi SMA's changed by secondary pulse electric current treatment by means of ultra small angle scattering and micro-computed tomography

Abstract

Porous NiTi samples were produced by two different techniques, Mechanical Alloying & Hot Pressing (MA&HP) and Reaction Synthesis (RS), followed by secondary Pulse Electric Current (PEC) treatment. The samples were analyzed by Ultra Small Angle Neutron Scattering and Computed Microtomography before and after the secondary treatment in order to investigate porosity of the samples. For the samples produced by MA&HP, PEC treatment does not cause any changes in pore size distribution for smaller pores (i.e.<10 μm). For bigger pores, however, treatment leads to a decrease of the pore volume along with the reduction of the amount of pores. In samples processed by RS, PEC treatment led to a decrease in pore dimensions of smaller pores (up to 10 μm), while for larger pores PEC treatment resulted in an increase in pore dimensions. Thus, the influence of secondary PEC treatment on the porosity of NiTi samples produced by the two different techniques could be confirmed and compared. Due to the pioneering character of the present work, further studies are required before using PEC treatment in future for porosity modification in a controlled manner.