Effects of orientation on hardness, strain accumulation, and fracture

Effects of orientation on mechanical properties of near α titanium alloy IMI834 have been investigated. Orientation dependent hardness was characterized by micro hardness testing and electron back scattered diffraction (EBSD). Strain accumulation of samples subjected to tensile, compression and Charpy impact tests at room temperature and at 650 °C was analyzed using EBSD. The [0001] orientation shows the highest hardness; lower values of hardness occurred for orientations along the [ 10 1 ¯ 0 ] [ 3 12 ¯ 0 ] axis. Differences in hardness between different orientations were discussed based on the activation of different slip and twinning systems. During tensile and Charpy impact tests at both temperatures, localized deformations restricted the strain accumulation at regions farther from the fracture surface. In both high-temperature tensile and compression tests, large orientation gradients occurred primarily at grains having lower hardness; however, the converse was not true. Apart from grain orientation, orientations of neighboring grains also have a strong influence on the development of orientation gradient. Irrespective of the test conditions and orientation, twinned regions accommodate considerably less strain and orientation gradient compared with those of the surrounding matrix.