Structural Features of TiNi-Based Biocompatible Porous Materials with Terraced Pore-Wall Surface Morphology

Abstract

An investigation of the structural features of TiNi-based porous materials, having terraced morphology of the pore-wall surfaces, manufactured by sintering is performed. Using liquid-phase diffusion sintering of a TiNibased powder, a porous alloy is manufactured where the fraction of the master phase TiNi is 78.6 wt.%. The distribution of the secondary phases Ti₂Ni, Ti₄Ni₂(О,N,С) and Ti₃Ni₄ in the porous materials is determined by the structure of the spongy and compact powder particles. The pore-wall surfaces of the resulting porous alloy exhibit terraced relief in all regions of the melt formation. The height of the steps is up to 0.25 μm for the width of the terraces 0.4–0.5 μm. The terraces are found on the areas free from the secondary-phase particles; they propagate across the curved pore-wall surface within one grain. In certain areas, there are hexagonal islands on the pore-wall surface, which measure from 1 to 2 μm. The terraced relief is formed as a result of volumeand surface diffusion during the interaction of the melt with the martensite B19′ crystals on the pore-wall surfaces. It is hypothesized that the mass transfer processes during the formation of terraces are affected by the phase content inhomogeneity and the creep deformation effect.