Microstructure and Properties of a Refractory NbCrMo0.5Ta0.5ZrTi Alloy (Preprint)

A new refractory alloy, Nb20Cr20Mo10Ta10Zr20Ti20, was produced by vacuum arc melting. To close shrinkage porosity, it was hot isostatically pressed (HIPd) at T = 1723 K and P = 207 MPa for 3 hours. In both as-solidified and HIPd conditions, the alloy contained three phases: two body centered cubic (BCC1 and BCC2) and one face centered cubic (FCC). The BCC1 phase was slightly enriched with Nb, Mo and Ta and depleted with Zr and Cr, and its lattice parameter after HIP was a = 324.76 plus or minus 0.16 pm. The BCC2 phase was enriched with Zr and Ti and considerably depleted with Mo, Cr and Ta, and its lattice parameter after HIP was estimated to be a = 341.0 plus or minus 1.0 pm. The FCC phase was highly enriched with Cr and it was identified as a Laves C15 phase, (Zr,Ta)(Cr,Mo,Nb)2, with the lattice parameter a = 733.38 plus or minus 0.18 pm. The volume fractions of the BCC1, BCC2 and FCC phases were 68.5%, 9.6% and 21.9%, respectively. The alloy density and Vickers microhardness were = 8.23 plus or minus 0.01 g/cubic cm and Hv = 5288 plus or minus 71 MPa. The alloy had compression yield strength of 1595 MPa at 296 K, 983 MPa at 1073 K, 546 MPa at 1273 K and 171 MPa at 1473 K. During deformation at 296 K and 1073 K, the alloy showed ductile fracture after plastic compression strain of approximately 5-6%. No macroscopic fracture was observed after 50% compression strain at 1273 K and 1473 K. Preprint journal article to be submitted to Acta Materialia. Prepared in collaboration with UES, Inc., Dayton, OH. This document contains color.