Papers by Author: Lian Xi Hu

Abstract: Nd2Fe14B/α-Fe nanocomposite powders with a nominal composition of Nd12Fe82B6 were prepared by HDDR combined with mechanical milling. The microstructure of both the as-disproportionated and the subsequently desorption-recombination annealed alloy powders was studied by Mössbauer spectrometry and TEM. The magnetic properties were investigated by VSM using bonded magnet samples. The results showed that the annealing temperature had significant influence on both the recombination kinetics and the grain size of the Nd2Fe14B/α-Fe nanocomposite phases, and the bonded magnet samples presented the best magnetic properties when the nanocomposite powders were prepared by annealing at 760°C for 30 min.

Abstract: Recent research at Harbin Institute of Technology on the synthesis of nanocrystalline and untrafine grained materials by mechanical alloying is reviewed. Examples of the materials include aluminum alloy, copper alloy, Ti/Al composite, magnesium-based hydrogen storage material, and Nd2Fe14B/α-Fe magnetic nanocomposite. Details of the processes of mechanical alloying and consolidation of the mechanically alloyed nanocrystalline powder materials are presented. The microstructure characteristics and properties of the synthesized materials are addressed.

Abstract: A 20vol.%SiCw/ZK51A Mg-based composite was fabricated by the process of semi-solid extrusion directly following liquid infiltration. The microstructure and mechanical properties of the composite were investigated in comparison with its squeeze cast and hot extruded counterpart. The results showed that, by semi-solid extrusion, the SiC whiskers were well aligned and microstructure defects associated with the casting technology were eliminated. In addition, as compared with the conventional hot extrusion, the damage to the SiC whiskers during semi-solid extrusion was reduced significantly. Consequently, the composite fabricated by the semi-solid extrusion presented the best whisker reinforcing effect, with its elastic modulus, 0.2% offset yield strength, and ultimate tensile strength achieving 82.5GPa, 383.6MPa, and 431.8MPa respectively.

Abstract: Numerical simulation of pressure influence on the relative densities of both solid and hollow cylindrical workpieces during Thixoforging was carried out by using ANSYS software. The results showed that there was a big difference in relative density between different points within the workpiece during Thixoforging with the use of a single punch. Therefore, partial feeding with the help of assembly punches was proposed to improve workpiece density uniformity and properties, and the effectiveness of this approach was well-demonstrated by numerical simulation.