Deformability enhancement in ultra-fine grained, Ar-contained W compacts by TiC additions up to 1.1%

Nano-sized Ar bubbles give negative influence on the fracture resistance and occurrence of superplasticity in ultra-fine grained (UFG) W-TiC compacts. In order to enhance cleformability in UFG, Ar-contamed W-TiC compacts, effects of TiC addition on the high-temperature deformation behavior were examined. W-TiC compacts with TiC additions of 0, 0.25, 0.5, 0.8 and 1.1 wt% were fabricated by mechanical alloying in a purified Ar atmosphere and hot isostatic pressing. Tensile tests were conducted at 1673-1973 K (0.45-0.54 T(m), T(m): melting point of W) at initial strain rates from 5 x 10(-5) to 5 x 10(-3) s(-1). It is found that as TiC addition increases, the elongation to fracture significantly increases, e.g., from 3 to 7% for W-0 and 0.25TiC/Ar to above 160% for W-1.1TiC/Ar when tested at 1873 and 1973 K at 5 x 10(-4) s(-1). The flow stress takes a peak at 0.25%TiC and decreases to a nearly constant level at 0.5-1.1 %TiC. The ranges of the strain rate sensitivity of flow stress, m, and the activation energy for deformation, Q, with TiC additions are 0.17-0.30 and 310-600 kJ/mol, respectively. The observed effects of the TiC additions on the tensile properties are discussed. (c) 2008 Elsevier B.V. All rights reserved.