Papers by Author: M.Y. Lu

Abstract: Notched tensile strength (NTS) of the Ti-6Al-4V (Ti-6-4) to Ti-6A16V-2Sn (Ti-6-6-2) dissimilar laser welds were determined, which had been subjected to post-weld heat treatment (PWHT) over the temperature range of 482-704°C. The results indicated for the weld with the PWHT at 482°C the fusion zone (FZ) and heat-affected zone (HAZ) showed a peak hardness, as compared with other welds at the counterpart regions, whereas, the weld with the PWHT at 704°C had the lowest hardness among the welds. In all the welds, the FZ of the weld subjected to PWHT at 482°C possessed the lowest NTS, while the as-welded and the weld with PWHT at 704°C had superior NTS to others. The presence of grain boundary α, which promoted grain boundary shear, accounted for the typical features of mainly transgranular fracture with intergranular dimples of the welds.

Abstract: Quasi-vertical ZnS nanostructures with different Ga doping level ( ZnS:Ga nanowalls ) have been synthesized in high yield from the mixed powders in the vacuum furnace at 1150 oC. ZnS:Ga nanowalls were grown vertically on the substrate with the size in the range of several microns and the thickness down to 15 nm and have very rough edges. The possible growth mechanism of nanowalls is likely governed by a vapor-solid (VS) growth mechanism. Room-temperature cathodoluminescence spectra of ZnS : Ga nanowalls show two emission peaks at approximately 443 nm and 578 nm. The emission mechanisms are discussed.