In this study, laser surface remelting of an AlCoCrFeNi_2.1 high-entropy alloy was performed using a Yb:YAG laser. The effects of laser surface remelting on the phase structure, microstructure, Vickers hardness, frictional wear properties, and corrosion resistance of the high-entropy alloy were investigated. The remelted layer of the AlCoCrFeNi_2.1 high-entropy alloy was produced by remelting at 750 W laser power and formed a good metallurgical bond with the substrate. The X-ray diffraction results showed that the 750 W remelted layer consisted of face-centered cubic and body-centered cubic phases, which were consistent with the phases of the as-cast AlCoCrFeNi_2.1 high-entropy alloy, and a new phase was not generated within the remelted layer. Laser surface remelting is very effective in refining the lamellar structure, and the 750 W remelted layer shows a finer lamellar structure compared to the matrix. The surface hardness and wear resistance of the AlCoCrFeNi_2.1 high-entropy alloy were substantially improved after laser surface remelting. In a 3.5 wt.% NaCl solution, the laser-remelted surface had a larger self-corrosion potential and smaller self-corrosion current density, and the corrosion resistance was better than that of the as-cast high-entropy alloy.

In this study, Al-17%Si alloys were dual modified by fine-grained structural materials (FSM) according to structural heredity. Microstructure and thermal analyses were undertaken to study the modification effect of the FSM master alloy on primary and eutectic Si. Primary Si is refined to a smaller size and eutectic Si is modified from needle-like to fibrous shape after FSM master alloy addition. The optimal content of FSM master alloy is 20% and the holding time is 15min. Finer FSM master alloy leads to finer Al-17%Si alloy microstructure and more area percentage of α-Al. DSC analyses results show that FSM master alloy can raise the precipitation temperatures of primary and eutectic Si, meanwhile it can reduce the latent heat of Si solidification process.

The nano-ZrO₂-reinforced AZ31 alloy composites were fabricated by friction stir processing with three multi-passes and high rotation speeds. The AZ31/2.14 vol% ZrO₂, AZ31/4.29 vol% ZrO_2, and AZ31/6.43 vol% ZrO₂ composites were designed. The fine microstructure and uniform dispersion of ZrO₂ particles were observed in the AZ31/ZrO₂ composites. The excellent interfacial bonding was observed between the Mg matrix and ZrO₂. The hardness and tensile properties were enhanced after three cumulative friction stir processing passes. This was attributed to grain refinement and strengthening effects of ZrO₂. The tensile properties and hardness of the AZ31/ZrO₂ composite increased with the increase of volume fraction of the ZrO₂ particles from 2.14 to 6.43 vol%.

The barrier properties and diffusion behavior of Cu(Re) alloy films were studied. The films were deposited onto barrierless SiO₂/Si by magnetron sputtering. X-ray diffraction patterns and electric resistivity results proved that the Cu(Re) alloy films without a barrier layer were thermally stable up to 550 °C. Transmission electron microscopy images and energy-dispersive spectrometry employing scanning transmission electron microscopy provided evidence for a self-formed Re-enriched diffusion layer between the Cu(Re) alloy and SiO₂/Si substrate. Furthermore, the chemical states of Re atoms at the Cu(Re)/SiO₂ interface were analyzed by X-ray photoemission spectroscopy. The self-formed diffusion layer was found to be composed of Re metal, ReO, ReO₂ and ReO₃. At 650 °C, the Cu(Re) layer was completely destroyed due to atom diffusion. The low electrical resistivity in combination with the high thermal stability suggests that the Cu(Re) alloy could be the ultimate Cu interconnect diffusion barrier.