Strength and ductility of powder consolidated ultrafine-grain tantalum

Abstract

Bulk ultra-fine grain tantalum was successfully fabricated from pure tantalum powder particles with an average particle size of 50 μm by equal channel angular extrusion at 900° C and 1200° C using three different processing routes. The effects of extrusion route and temperature on the consolidation performance are evaluated through microstructural analysis and room temperature mechanical testing. The consolidated tantalum has a “wood grain” like structure with strong interparticle bonds and a grain size <100 nm. The lamellar structure is helpful in resisting crack formation and fracture. The bulk tantalum consolidates are much stronger than annealed wrought tantalum and have significant ductility. Tensile tests for consolidated tantalum at room temperature show a yield strength of 340–376 MPa, an ultimate strength of up to 618 MPa, and strains to failure of ~19–25%. These properties are comparable to wrought Ta. The present study demonstrates that equal channel angular extrusion is a feasible method for fabricating bulk nanostructured refractory alloys from precursor powder, with a combination of high strength and good ductility.