Metallographic Characterization of Laser Peened Ti6Al4V Subjected to Hydrogen Charging.

In this article, slow strain rate tensile (SSRT) test were carried out on laser peened hydrogen charged Ti6Al4V samples to analyze the effect of hydrogen on mechanical properties. Ti6Al4V alloy subjected to two different laser peening conditions is investigated using transmission electron microscope (TEM) and electron backscatter diffraction (EBSD) to understand the grain refinement and texture orientation. The microstructural images of TEM indicated the existence of newly formed grain boundaries, slip bands and hexagonal networks. The bright-field image of line like structure demonstrate the formation of 10 1 ¯ 1 twin which indicates the occurence of β/α′ martensitic transformation. Accumulation of dislocations and shear bands formed during laser peening played an important role preserving the mechanical properties even after samples subjected to hydrogen charging. Test sample, laser peened with ablation coating and hydrogen charged shown a loss of elongation δ L with 14.11% compared to test sample laser peened without ablation coating and hydrogen charged shown 19.16%, indicating that sample peened with no ablation have significance in reduction of elongation loss. Both the samples shows the reduced tensile strain at break (standard) % compared to as-received test sample. Test sample laser peened without ablation coating shown high strain rate deformation and intense grain refinement at top surface due to the adiabatic temperature. The experimental results demonstrate that the laser peening has considerable desired effect in protecting mechanical properties of Ti6Al4V alloy even after subjected to hydrogen charging. [ABSTRACT FROM AUTHOR]