Dynamic Response of TI2ALC Under Radial Confinement at High Temperature

Abstract

Experiments were performed to evaluate the dynamic mechanical response of MAX phase material Ti2AlC at high temperature (HT) and under radial confinement.A Split Hopkinson Pressure Bar (SHPB) apparatus was employed to conduct experiments at a strain rate of 500 s 1. High speed photography was used to capture the dynamic response of unconfined specimens. An induction coil was used to heat the specimens from 25 to 1000°C. Nickel-cobalt-ferrous alloy (Kovar) shrink fit sleeves were utilized to produce a mechanical radial pressure of 30 to 195 MPa. Unconfined room temperature (RT) and HT experiments revealed that Ti2AlC fails in a gradual brittle (also referred to as graceful failure) manner with a low dependency on temperature up to 800°C. All experiments conducted with radial confinement produced a fully plastic response without failure. The addition of hydrostatic confinement increased the maximum compressive stress for all temperatures and allowed specimens to reach strains in excess of 8% without failing. Optical and Scanning Election Microscopy (SEM) images were taken of the cross-section of recovered confined specimens. Imaging revealed conical damage patterns on each end of the specimen which facilitate the plastic response.iii ACKNOWLEDGMENTS