Activated slip and twin systems in electron beam melted Ti-6Al-4V subjected to elevated and high strain rate dynamic deformations

This study presents an investigation on the effect of elevated (700 s(-1)) and high strain rate (2100 s(-1)) on the dynamic mechanical properties and deformation mechanisms of electron beam melted (EBM) Ti-6Al-4V cylindrical rod printed in the horizontal orientation. Optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) techniques were utilized to characterize the microstructural and texture evolution. The typical microstructure consists of transformed alpha+beta phase, grain boundary-alpha (alpha(GB)) along prior beta-grain boundaries that are near-parallel to the build direction. Dynamic impact tests were conducted at room temperature using a Split-Hopkinson pressure bar (SHPB) apparatus, where the build direction is perpendicular to the impact loading. The dynamic mechanical properties of the sample deformed at the strain rate of 2100 s(-1) exhibited higher compressive strength (similar to 250 MPa) and total strain (similar to 13%) that of the sample deformed at the strain rate of 700 s(-1). Compared to the as-built sample, deformed samples exhibited finer microstructure, lesser alpha-interlamellar spacing, and higher alpha-lamella's fragmentation with the increase in the strain rate. EBSD Schmid factor distribution maps were used to discuss the effect of the initial texture and the strain rate on the deformation mechanisms' possible changes.

Automated summary

This study investigates the dynamic mechanical properties and deformation mechanisms of electron beam melted Ti-6Al-4V cylindrical rod at elevated and high strain rates. The results show that samples deformed at higher strain rates exhibit higher compressive strength and total strain. With the increase in strain rate, the microstructure becomes finer and there is an increase in the fragmentation of alpha-lamella.