Microstructure and metallic ion release of pure titanium and Ti-13Nb-13Zr alloy processed by high pressure torsion

Significant enhancement of mechanical properties of metallic biomaterials can be achieved by grain refinement obtained by severe plastic deformation. The purpose of this study was to determine metallic ion release from commercially pure titanium (CPTi) and Ti-13Nb-13Zr alloy processed by high pressure torsion (HPT). The materials microstructures, in the initial state and after HPT deformation, were examined by scanning and transmission electron microscopy. The microhardness was determined along the radius of the disc-shaped samples of ultrafine-grained (UFG) CPTi and Ti-13Nb-13Zr alloy in order to evaluate homogeneity of HPT-processed materials. The quantities of released ions were determined using inductively coupled plasma-mass spectrophotometer for samples immersed in artificial saliva at 37 degrees C for 7 days. Also, the effect of artificial saliva pH value on metallic ion release was estimated. Obtained results revealed that the quantities of released ions from UFG CPTi and Ti-13Nb-13Zr alloy obtained by HPT process were higher than the quantities of released ions from CPTi and Ti-13Nb-13Zr alloy produced by traditional casting. This behavior can be explained by the fact that metallic ions are easily released from microstructure with smaller grains achieved by HPT process. (C) 2015 Elsevier Ltd. All rights reserved.