Effects of grain orientation and confinement on dynamic compressive behavior of highly oriented MAX phase Ta₂AlC

MAX phases are unique ternary carbides and nitrides that bridge the gap between metals and ceramics. Specifically, Ta₂AlC, the MAX phase with the highest bulk modulus, offers a unique combination of metallic and ceramic properties, making it particularly well-suited for extreme applications. Fully dense, coarse-grained, and textured Ta₂AlC was fabricated in bulk, achieving a global grain orientation along the c-axis with an orientation factor of 0.63. The uniaxial quasi-static and dynamic, and biaxial dynamic response was evaluated parallel (∥) and perpendicular (⊥) to the c-axis. The average dynamic strength in ⊥ c-axis orientation was 824 ± 39 MPa, 19 % higher than the uniaxial quasi-static compressive strength of 690 ± 55 MPa in the same orientation. The biaxial dynamic strength in this orientation, when applying a moderate 80 MPa planar confinement along basal planes (⊥_∥ c-axis) had the highest average compressive strength of 1097 ± 72 MPa. Scanning electron microscopy fractography indicates a consistent fracture mechanism within the grain orientation across different strain rates under uniaxial loading. During biaxial loading, crack propagation was delayed, with qualitative indications of shear band formation. Concurrently, both the quantity and mode of kink band formation appeared to increase, leading to an overall enhancement in final strength. The link between macroscopic failure behavior captured from ultra-high-speed imaging and microscopic fractography is discussed.