Papers by Author: Wan Qiang Xu

Abstract: An In-situ Mg-based bulk metallic glass (BMG) composite containing 40% volume fraction of Mg-rich crystalline flakes was produced by die casting. During cooling from the melt, the flakes nucleate heterogeneously and subsequently grow with their broad faces parallel to the {0001} plane. This generated a uniform dispersion of randomly-oriented flakes within an amorphous matrix. When compressed uniaxially up to 60% reduction in the supercooled liquid (SCL) region, the flakes in this composite were substantially aligned their broad faces towards the compression plane that generated a strong //ND fibre texture.

Abstract: It is possible to produce a nanocrystalline, multilayered composite structure with enhanced mechanical properties by assembling three 316L surface nanostructured stainless steel plates by roll bonding. The Surface Mechanical Attrition Treatment (SMAT) was first used to generate nanocrystalline layers on the elementary plates so that their mechanical properties were improved. They were then assembled through co-rolling. A composite structure of nanocrystalline layers of high strength alternating with more ductile layers was obtained to achieve both high strength and ductility. Microscopy observations and EBSD measurements were carried out and the bonding interfaces were analysed in detail to explore the mechanisms involved during the SMAT/Co-rolling duplex process.

Abstract: 3-D FIB-EBSD tomography was used to analyze the structure and crystallography of nuclei, and nucleation process in 3-D space during annealing a cold rolled IF steel. It is revealed that the structure of nucleus at its very initial formation stage can be divided into two parts: (1) nucleation core, having a dislocation-contained subgrain structure, mainly bounded by low angle grain boundary with surrounding deformation subgrain, (2) newly-grown region, having a dislocation free structure, formed from high store energy deformation structures surrounding nucleus, and mainly bounded by high angle grain boundary.