Papers by Author: Hitoshi Hashimoto

Abstract: Multiple target magnetron sputtering technique was employed for the deposition of (Cr,V)2AlC thin films, on the substrate of Si wafer at temperatures ranging from ambient to 840 K. The chemical composition and crystal structure of the deposited thin films were analyzed, surfaces as well the cross sections observed. The experimental results demonstrated that the temperature of the substrate does not affect the chemical composition of the deposited thin films. Deposition at room temperature or moderate elevated temperatures was found to result in amorphous films, whereas crystalline MAX phase thin films were obtained at high temperature. The transition of the substrate temperature was found to be around 743 K. The thin films deposited at temperatures below the transition showed the featureless flat surfaces. At high substrate temperatures, crystalline MAX thin films were formed. When deposited at temperatures near the transition, amorphous/nanocrystalline double layer thin films were deposited.

Abstract: The tensile properties of two MoSi₂ alloys with different grain sizes (1 micrometer and 10 micrometer) were evaluated in vacuum at temperatures ranging from 1400 to 1600K and initial strain rates ranging from 1×10-5/s to 1×10-3/s. For the alloy with 10micron grain size an m vale of 0.35 and an activation energy value of 350 kJ/mol were observed in the lower strain rate range while an m value of 0.12 and an activation energy value of 760 kJ/mol were observed in the higher strain rate range. For the alloy with 1micron grain size, a uniform m value of 0.55 and an activation energy value of 160 kJ/mol were observed. Moreover these two alloys showed remarkable ductility (maximum 33%) in the test temperatures. The deformation mechanism and the remarkable ductility are discussed in the light of the microstructural observations through SEM and TEM.