Papers by Author: Jing Jie Guo

Abstract: The modifiers of nano-SiC and nano-TiN were added into the melt of ZGMn13Cr2 alloy, respectively. The effect of the additions on the microstructure and mechanical properties were investigated. Results show that the two kinds of nano modifiers both have refining effect and make the improvement of impact toughness and wear resistance.

Abstract: The effect of major parameters, such as pouring temperature, tilt time and preheating temperature of mold, on the tilt casting of aluminum alloy automobile drain pipes is studied through numerical simulation using single factor and orthogonal test methods. The simulation results of single factor test indicate that the increase in the pouring temperature and mold preheating temperature could effectively reduce the shrinkage tendency and the shortage of tilt time would cause lower temperature gradient of casting at the beginning of solidification, thus would lead the extension of solidification time. And the results of orthogonal test showed that the sequence of factors having effect on the filling and solidification process, are pouring temperature, tilt time and preheating temperature of mold. Finally, combined the result of single factor test with orthogonal test, an optimized tilt-casting process was proposed by investigating the velocity distribution at each stage of the filling process and the isolated area distribution of liquid phase in the solidification process, and by predicting the position of porosity in the casting. The effectiveness of the proposed process parameters in producing high quality castings is also proved through numerical simulation.

Abstract: Developing high performance aero-engines usually depends on the development of new candidate materials with charming properties such as relatively light-weight, good high temperature strength and environmental resistance. Fortunately, γ-TiAl alloys were followed into this catalogue that they offer a significant potentiality for weight savings. Recently, in order to improve their low room temperature plasticity, a motive technology called electromagnetic cold crucible directional solidification technology for preparation γ-TiAl alloy ingots with directional growth structure was put forward by our group. By the approach, TiAl ingots with controllable lamellar structures and less impurity contaminations are obtained. Typically, Ti-46Al-0.5W-0.5Si and Ti-47Al-2Cr-2Nb were performed with respect to compositions and solidification parameters. As a result, Ti-46Al-0.5W-0.5Si DS-samples exhibit good combination of mechanical properties at room temperature in TS of 500MPa and EL of 2% in average. Meanwhile TS of DS Ti-47Al-2Cr-2Nb reaches 650 MPa and EL exceeds 3%.

Abstract: Effects of parameters on the stability of silicon melt pool in cold crucible continuous casting were discussed. The results indicate that the extinguishing of induction heating is mainly caused by the side wall feeding, low superheat degree and volume of the pool. The hot melt splashes are caused by the higher input power and uncompletely melted silicon of the dome top surface. The pool was shown to be stabilized as the raw materials were fed in the center area of the dome surface, the superheat degree and volume of the pool were properly increased, the pool was controlled in the effective heating range of the coil and the input power was set properly

Abstract: The effects of technical parameters on initial silicon melting in cold crucible continuous casting were studied. These parameters include the materials, the shape and the position of the base, the mass of the silicon that set on the top of the base. Through experimental and theoretical analysis, the optimized parameters were finally given: the base graphite with obconical shaped should be put at the level of the second turn of the coil, and the initial silicon with 10g should be put on the base. The mechanism of these parameters affecting on the initial melting are discussed and revealed.

Abstract: In this study, Ti46Al0.5W0.5Si ingots were directionally solidified by a near-rectangular cold crucible under different process parameters. These process parameters include the electromagnetic stirring, the crucible configuration and the molten drop, all of them have important effect on the S/L interface. The effects of the parameters on the solid/liquid (S/L) interface morphology were investigated, and the mechanisms of the parameters influencing the S/L interface were discussed and revealed. Results showed that the typical S/L interface of the ingots was presented as a curved ‘W-type’ shape. The uneven temperature distribution in the front of the solidified interface is the main reason for a curved S/L interface. Further, the requirements for obtaining a planar S/L interface in the process of cold crucible directional solidification were given, which provided a guide for the future work.

Abstract: Abstract. For efficiently performing the numerical simulation of electromagnetic continues casting (EMCC) with finite element method (FEM) and finite volume method (FVM) combined scheme, a program integrates with data-format conversion and post-processing was proposed. The conversion of data format realized by linear interpolating, and the post processor developed on a Visual Fortran 6.6A platform using Fortran-95 language and the QuickWin module. Both 2-D and 3-D EM-FEM data calculated by a general-purpose FEM software, ANSYS, could be converted into FVM-data format using this program, and all FVM-data whether scalar quantities or vector ones could be displayed in the manners of cabinet drawing and normal axonometric drawing, which promises the correctness for data format conversion process of FEM/FVM-joint and the convenient analysis of transport phenomena during EMCC numerical simulation. The results of transport simulations and data format conversions indicate that the format-conversion method as well as the post processing is effective and convenient in numerical simulation with FEM/FVM-joint under various EM fields.

Abstract: This paper gives a detailed study of temperature distribution on Ti46Al0.5W0.5Si alloy directionally solidified by cold crucible. Based on experiment and numerical calculation, the heating process under different power was investigated, and the operating efficiency of cold crucible was roughly calculated. Further, the temperature field of Ti46Al0.5W0.5Si alloy under high power was numerically calculated, the finite element model predicted the temperature distribution at different moment. The results give a significance guide on cold crucible directional solidification.

Abstract: A square shaped silicon ingot was cast by cold crucible continuous casting. The grain growth behaviors during different growth stages were investigated. In the first, grains nucleate at the base surface in the centre and in the three phase junction at periphery, and then grow upwards and inclined upwards separately. In the second, grain grow competitively, two distinguished zones are formed. In the final, a cap is formed on the liquid free surface, and precipitates are present.

Abstract: The ingot of Ti47Al alloy was prepared by a newly developed rapid directional solidification, the microstructure and compressive properties of the ingot was observed and tested. The results show that the macrostructure consisted mainly of coarse columnar grains parallel to the axial direction, with the size of 0.5mm wide and 10mm in length. The direction of lamellar is almost perpendicular to the growth direction in the longitudinal section and no dendritic core is found. The average ultimate compressive strength of the specimens with grain growth parallel/perpendicular to the compressive direction is 1233.3 and 861.7 MPa respectively. The fracture mode for specimens with grain growth parallel to the compressive direction exhibits predominantly translamellar fracture, however, that for specimens with grain growth perpendicular to the compressive direction exhibits predominantly delamenation or interlamellar fracture.