Strain uniformity footprint on mechanical performance and erosion-corrosion behavior of equal channel angular pressed pure titanium

Abstract

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure, mechanical, and erosion-corrosion behavior of commercial pure (CP) titanium was investigated through experimental work. Four passes of ECAP processing at 400 ℃ was performed on CP titanium. The results showed that the homogeneous structure and coarse equiaxed grains of the initial annealed sample are transformed into the combination of UFG and NS with an average size of 750 nm and 85 nm, respectively. Also, ECAP pass numbers increase the fraction of high angle grain boundaries which improves the ductility of the processed sample. The highest hardness and strength improvement rate was observed after the first pass. Furthermore, the increasing rate of hardness and strength is gradually decreased at the subsequent passes and reached the steady-state level at the 4th pass. This is due to the balance between hardening by dislocations and twinnings accumulation and softening by recovery mechanisms. As a result, a uniform hardness distribution on both the cross-sectional and longitudinal planes is achieved. It was confirmed that erosion-corrosion resistance of the processed sample is enhanced due to the grain refinement, material homogeneity, and quick formation of a strong oxide bond layer on the surface.