Papers by Author: Bi Cheng Yang

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Authors: Bi Cheng Yang, Shao Ming Zhang, Jun Xu, Li Kai Shi, Z. Fan
Abstract: The billet of magnesium AZ31B was made by twin-screw rheo-cast, and the specimen cut from the rheo-cast billet and normal cast billet were compressed in Gleeble-3000 hot simulator. The deformation temperature was 300, 350, and the strain rates were 0.001~1s-1. The relationship among flow stress, deformation temperature and strain rates were analyzed. The variation of the microstructure was observed and compared after the specimen was hot compressed. The results show that the surface of the rheo-cast specimen is much more smooth than the normal cast specimen after the compression. The dynamic recrystallization had taken place during the compression and the recrystallized grain of rheo-cast sample is more tiny than normal cast specimen.
Authors: Xiao Gang Hu, Bi Cheng Yang, Jun Xu, Hai Jun Wang
Abstract: The hot deformation behavior of hypereutectic aluminium-silicon alloy was investigated by thermal simulation test at the deformation temperature of 330-480 and the strain rate of 0.1-10s-1 using the Gleeble-1500 thermal mechanical simulator. The relationship of flow stress, temperature and strain rate was appropriately described by the deformation constitutive equation, and the deformation activation energy is 187.418 KJ/mol. In addition, the microstructures of these specimens were analyzed and the result showed that the inhomogeneous deformation enhances with increasing strain rate and decreasing deformation temperature, and the presence of primary silicon had a strong influence on the uneven deformation.
Authors: Jun Xu, Shao Ming Zhang, Bi Cheng Yang, Li Kai Shi, Z. Fan
Abstract: A new rheo-extrusion technique has been developed to produce extruded profiles. The AZ31 slurry is fabricated by a twin-screw mechanism, and has spheroidal solid particles with a grain size of about 50 to 80μm. The slurry was introduced into an extrusion container with an inner diameter of 95mm, and then squeezed to a billet before extruding into a round bar with a diameter of 22mm using a 500kN extrusion machine. It is found that the new technique has a lower deformation resistance than that of the conventionally hot extrusion technique in the same extrusion velocity. The microstructure and mechanical properties of the rheo-extruded bars were examined in detail. The results illustrated that grains of the bar were very fine with the average grain size about 2.3μm,and the mechanical properties were improved substantially compared with those of the same alloy produced by the conventional hot extrusion.
Authors: Li Jun Xie, Jun Xu, Bi Cheng Yang, Zhi Feng Zhang, Li Kai Shi
Abstract: An application of the semi-solid alloy Al-6Si-2Mg to produce automobile components was carried out for farther development of this new alloy. The experiments were done in a self-developed SSM trial line composed of semi-continuous caster combined with electromagnetic stirring for feedstock billet production, 6-station induction reheating equipment for restoring thixotropy of SSM billet and modified die-casting unit for semi-solid thixoforming. The results show that Al-6Si-2Mg alloy has such a suitable fraction solid and low temperature sensitivity of fraction solid that the controllability of SSM process is increased greatly. The billets have uniformly fine microstructure with a higher degree of sphericity and also retain good thixotropic properties. During thixoforming, the die is filled completely, the microstructure of components is dense, and the primary phases are near spherical, and the mechanical property after heat treatment has good performance.
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