Papers by Author: Yu Man Zhu

Abstract: The effect of heat treatment on tensile properties, especially pseudoelastic behaviour of hot-rolled Ti-25Nb-3Zr-3Mo-2Sn (wt.%) alloy has been studied. The as-rolled alloy shows high strength due to the presence of nanoscale ω and α precipitates, but it suffers from limited ductility. The conventional solution plus ageing treatment improves the ductility, but it has an adverse effect on the psudoelastic properties. By applying flash treatment (500 °C for 2 min), the alloy is found to have not only balanced strength and ductility, but also improved psudoelastic properties, such as higher recovery strain and lower elastic modulus. The microstructural changes associated with the flash treatment are revealed.

Abstract: The structure of intermetallic phases and planar defects in the as-cast and the solutiontreated microstructures of a Mg-8Y-2Zn-0.6Zr (wt%) alloy are characterized using transmission electron microscopy. The alloy was produced by permanent mould casting and solution treated at 500 °C. It is found that the intermetallic particles in the as-cast microstructure have a monoclinic structure. An appreciable amount of intermetallic particles is still retained along grain boundaries after solution treatments for up to 60 hrs. However, the structure of the retained intermetallic particles changes gradually from monoclinic to hexagonal during the solution treatments. Some planar defects are also detected in the as-cast and the solution-treated (1 hr) microstructures. These defects have characteristic features of stacking faults.