Chen Jingchao

Micromodel of Simulation on Twin-Roll Continuous Casting Thin Strip Solidification Structure

Abstract Based on the research on the solidification of twin-roll continuous casting aluminum alloy thin strip, the analytical model of heterogeneous nucleation, the growth kinetics of tip (KGT) and columnar dendrite transformation to equiaxed dendrite (CET) of twin-roll continuous casting aluminum alloy thin strip solidification are established by means of the principle of metal solidification. Meantime based on the cellular automaton(CA), the emulational model of twin-roll continuous casting aluminum alloy thin strip solidification is established. The foundation for the emulational simulation of twin-roll continuous casting thin strip solidification structure is laid. Last, the numerical simulation can provide some theoretical guidance for twin-roll continuous casting thin strip. Meanwhile it has confirmed the mathematical simulation feasibility by the solidification process of twin-roll continuous casting aluminum alloy thin strip

Micro-Superplastic Behavior of Copper Oxide in AgCuO Composites

Abstract In the investigation of AgCuO composites, we have found a type of copper oxide particles with a superplastic deformability behavior, which is similar to that of metals. To find the reason of the deformability of the copper oxide particles. SCM, STEM and TEM were used to analyze their crystal structures in AgCuO composites, The results show that the copper oxide particles with micro-superplasticity in the composites have cubic crystal structure, and their maximum elongation can be up to 300%, The copper oxide particles with no micro-superplasticity in the composites have monoclinic crystal structure. But the micro-superplastic behavior and mechanism of the copper oxides with the cubic crystal structure are not clear for the time being, the further investigation could be needed.

Simulation of Grain Growth during Solidification of Twin-Roll Continuously Cast Pure Aluminum with a Modified CA Model

Abstract A new mathematic model for the nucleation and the dendrite growth of twin-roll-continuously cast pure aluminum thin strip during solidification process was developed based on cellular automaton(CA)-finite element(FE) method and the classical transfer equations during dendrite growth. The model coupled the temperature field calculation and microstructure simulation. The solute diffusion, the curvature undercooling and the latent heat releasing were also considered in the model, all of which have significant influence on the dendrite evolution. So the dendrite growth morphology can be modeled. The applications of the model in equiaxed dendrite growth, multiple equiaxed dendrite growth, columnar grain growth, and columnar dendrite transformation to equiaxed dendrite in twin-roll-continuously cast aluminum thin strip solidification were presented. The microstructure simulation results were compared with the experimental results and they were in good agreement in dendrite morphology.

Research Progress on Brittleness of Iridium

Abstract Due to the high melting point, excellent high temperature strength and anticorrosive property, iridium is the unique material which can be used under extremely hostile environments. However, iridium exhibits an anomalous brittle fracture behavior, a mixed brittle intergranular fracture (BIF) and brittle transgranular fracture (BTF), even though it is of face-centred cubic (fcc) crystal structure. A great deal of efforts have been made to explore the embrittlement mechanisms since the anomalous fracture behavior was recognized in 1960 s, up to now, there has not been a reasonable conclusion yet. This paper emphatically reviewed the possible embrittlement mechanism of iridium, including impurity-induced brittleness, intrinsic brittleness and special defect structure induced embrittlement, discussed the research status quo about the deformation and failure mechanisms of iridium. Finally, the research direction and research method of the embrittlement mechanism of iridium were forecasted.

Effect of Cumulative Severe Plastic Deformation on Microstructure and Properties of Ag-CeO2 Composites by RSP

Abstract In present study, Ag-CeO2 composites were prepared by reaction synthesis processing. The phases, the procedure of microstructure homogenization, and the microstructure and physical property evolution of the Ag-CeO2 composites via the severe plastic deformation were researched extensively. XRD, SEM and EDS analysis indicate that the Ag-CeO2 composites with tiny AgCeO2 clusters forming in the Ag matrix can be obtained by reactive synthesis processing, and the microstructure shows the tiny CeO2 clusters distribute in the Ag matrix which becomes homogenous and dispersed after cumulative severe plastic deformation. The tensile strength and electrical resistivity decrease with the increase of true strain, while the elongation changes contrarily.