Direct observation of three-dimensional transient temperature distribution in SiC Schottky barrier diode under operation by optical-interference contactless thermometry (OICT) imaging

We have developed optical-interference contactless thermometry (OICT) imaging technique to visualize three-dimensional transient temperature distribution in 4H-SiC Schottky barrier diode (SBD) under operation. When a 1 ms forward pulse bias was applied, clear variation of optical interference fringes induced by self-heating and cooling were observed. Thermal diffusion and optical analysis revealed three-dimensional temperature distribution with high spatial (≤ 10 μm) and temporal (≤ 100 μs) resolutions. A hot spot that signals breakdown of the SBD was successfully captured as an anormal interference, which indicated a local heating to a temperature as high as 805 K at the time of failure.

Numerical and Experimental Investigations on Deposition of Stainless Steel in Wire Arc Additive Manufacturing

This paper presents numerical and experimental investigations on wire arc additive manufacturing for deposition of 430L ferritic stainless steel. Finite element analysis was used to predict temperature distribution for deposition of multiple layers in wire arc additive manufacturing. The transient temperature distribution and predicted by finite element simulation was in good agreement with the experimental results. A wall type structure was fabricated by deposition of multiple layers vertically, and deposited material was characterized by tensile testing and microstructure study. The microstructure of the deposited wall structure was investigated through optical microscopy and scanning electron microscopy (SEM) with EDS. The microstructure of deposited material was changed from fine cellular grains structure to columnar dendrites structure with the formation of secondary arm. It was found that the YS, UTS, and EL of the deposition direction were better than the build direction. The mechanical properties of the WAAM manufactured material was found comparable to that of the wire metal.