316LN is a type of austenitic stainless steel whose grain refinement only depends on hot deformation. The true stress–strain curves of 316LN were obtained by means of hot compression experiments conducted at a temperature range of 900–1200°C and at a strain rate range of 0·001–10 s−1. The influence of deformation parameters on the microstructure of 316LN was analysed. Both the constitutive equation for 316LN and the model of grain size after dynamic recrystallisation were established, and the effect of different deformation conditions on the microstructure was analysed. The results show that the suitable working region is the one with a relatively higher deformation temperature and a lower strain rate, in which the dynamic recrystallisation is finely conducted. Moreover, the working region that should be avoided during hot deformation was indicated.
Based on the theoretical model and physical mechanism of dynamic recrystallization (DRX) in metal materials, the dislocation density change, nucleation and grain growth model during the process of DRX are taken into account. And according to the nucleation driven by dislocation and grain growth kinetic, transformation rules are made. A modeling methodology coupling fundamental metallurgical principles based on amended nucleation rate with the cellular automaton (CA) technique is here derived to simulate the 316LN.The two-dimensional CA model uses quadrilateral element and periodic boundary condition and Von-Neumann neighbor type. The influence of strain, strain rate and deformation temperature on dynamic recrystallization volume fraction and average grain size are analyzed on the basis of established CA model.
In order to realize the mechanized transplanting of rice pot seedling and ensure our food security, The pitch curve of non-circular gear is fitted based on cubic, non-uniform and rational B-spline curve. The planetary gear train transplanting mechanism has been invented for ride type, and kinematics mathematical model has been built through the kinematics analysis of transplanting mechanism. The computer aided analytical and optimized software has been developed by using software platform of Matlab. Through tuning the data points by man-machine interaction, pitch curve of non-circular gear is optimized and structural parameters are obtained, which can meet the demand of track and attitude in the transplanting process for rice pot seedling. In condition of the parameters, the correctness of the established model is verified by the virtual experiment by software of Adams.
The established cellular automata model of dynamic recrystallization for 316LN simulated microstructure evolution of recrystallization nucleation and grain growth under different conditions. And on the basis of cellular automata model, the influence of strain, strain rate, deformation temperature on dynamic recrystallization behavior was analyzed. Though the hot compress experiment done on the Gleeble-3500 thermo mechanical simulator, combined with metallographic experiment, the microstructure at deformation temperature of 950 oC, 1050 oC and 1150 oC with strain rate of 0.001 s-1, 0.01 s-1, 0.1 s-1 and 1 s-1 was obtained. Simulation results are compared with metallographic microstructure, the error is small.
Mullite with puncheon-like grains was synthesized by sintering the mixtures of coal gangue and γ-Al2O3 at 1400 °C~1550 °C for 4 h. The phase and microstructure evolution of the mullitization behavior were investigated by XRD, SEM and EDS. Phases of the sintered specimens were mullite, corundum and cristobalite at 1400 °C to 1450 °C. Arise of temperature would enhance mullitization, and total consumption of cristobalite occurred from 1500 °C upward. The in-situ produced primary mullite from gangue upon heating may be seeds for the growth of enenly dispersed mullite puncheons. Specimen sintered at 1550 °C consists of puncheons with an aspect ratio of 2~4, regionally forming an interlocking structure.
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