Papers by Author: Laszlo J. Kecskes

Abstract: Severe plastic deformation (SPD) has been demonstrated to be the most efficient method to produce bulk metals with ultrafine grained (UFG, 100 nm < grain size d < 500 nm) and nanocrystalline (NC, d<100 nm) microstructures. Such metals exhibit some unique properties owing to their unusual microstructures such as high-energy, non-equilibrium grain boundaries. Efforts in the past two decades have focused on metals with face-centered cubic (fcc) structures. Recent experimental results have shown that UFG/NC metals with body-centered cubic (bcc) structures have some properties that are distinct from their fcc counterparts. Further, the majority of the fcc metals are very ductile and have relatively low melting points, making them easier to process using SPD. On the contrary, many bcc metals are refractory, and are very sensitive to interstitial impurities, rendering them difficult to work via SPD. In this article, we attempt to summarize the state-of-the-art of UFG/NC refractory metals processed by SPD, with focus on the microstructure and mechanical properties. Comparisons with UFG/NC fcc metals are made where appropriate. Outstanding issues and future directions are also addressed.

Abstract: WC + Ni-clad Al, Ni(Al), powder mixtures were formed into cylindrical rods or tubes using a hot explosive consolidation (HEC) process. During HEC, the Ni(Al) precursor, in the WC + Ni(Al) mixture, was found to react to form a WC-AlNi composite structure. The composite consisted of WC particles dispersed in a matrix of Al-Ni intermetallic phases. The consolidation temperature was varied from room temperature to 800°C; the shock loading intensity was as high as 10 GPa. The investigation showed that the combination of high temperatures and explosive compression was beneficial to the consolidation of the WC-AlNi composites, resulting in high densities, good integrity, and the formation of transient layer between the sample and the steel container’s wall. The structure and property of the samples obtained, and the formation of the transient layer depended on the shock loading conditions and the consolidation temperature. Features of the consolidated WC-AlNi samples as a function of the loading conditions (experimental set-up, loading intensity, and preheating temperature) are discussed.