Papers by Author: Jian Yih Wang

Abstract: Magnesium alloys and very light metals that can be used for structural application. A variety of Mg-Li-Zn alloys including Mg-11%Li-1%Zn, Mg-9%Li-1%Zn, Mg-9%Li-1%Zn-0.2%Mn, Mg-9%Li-1%Zn-1%Al-0.2%Mn and Mg-9%Li-3%Al-1%Zn-0.2%Mn were processed by equal channel angular extrusion (ECAE) to see how effective is this process in refining the grain structure. After 4 passes of the ECAE process, TEM studied the microstructural diversifications, especially showing the existence of compounds, MgLiZn, MgZn2 and ZnO. The room temperature and high temperature mechanical properties were also investigated. After the ECAE process, the room temperature strength was found enhanced at a modest cost of reduction in elongation.

Abstract: Five oxidized metallic alloys, namely, Crofer22, equivalent ZMG232, stainless steel SS430, SS304 and Inconel718 were subjected to oxidation treatment in hot air environment for various period of time. Then the resulted oxide scale was analyzed by scanning electron microscopy (SEM), electron probe micro analyzer (EPMA) and X-ray diffraction (XRD). All the five alloys contain comparable amount of Cr, Mn, Fe, and their surface oxides as analyzed indicate to be Cr2O3 and (Mn, Fe)Cr2O4 spinel compound.

Abstract: A practical and important idea regarding solid state recycling of magnesium alloys is explored. Chips of AZ91D have been put in hot air environment for accelerated oxidation to simulate the to-be-recycled state of Mg alloy scraps. These chips materials received extrusion process and subsequent annealing treatment. Tensile tests showed that the extruded plate had higher strength than that of ordinary die cast counterpart. Micro-structure investigation indicated it was probably due to finer grains of the Mg matrix as a result of extrusion. Further annealing did not seem to alter this fine structure, yet it could diminish some un-favored form of Mg17Al12 compound. Thus, post-annealed solid state recycled AZ91D showed impressive strengths and elongations.

Abstract: Among the conventional and alleged bulk deformation processes in metalworking, equal channel angular extrusion (ECAE) is an innovative and attractive method to refine grain structures effectively. Grain refining by this process on magnesium alloy AZ31 was studied and compared to published data. An interesting and unique question is proposed and studied - that is, how dominant is the accumulated strain as obtained through multiple angular extrusion passes. Tensile tests were performed at room and high temperatures, and processed AZ31 was examined with optical and transmission electron microscopy as well as x-ray diffraction.