Advanced Materials Research Vols. 476-478

Abstract: Anthracite carburant is adopted to increase the carbon during the steel tapping of the converter of Panggang, however, it is found that the smelting time is long and the yield rate of the carbon is low which severely affect the precision control of the heat composition, so the new type of carbon-manganese alloy carburant is developed and the application effect to the industry is investigated. The results show that this new type carbon-manganese alloy carburant smelting much faster, and the yield of the carbon and manganese are high, the average yield of carbon is 92.95%, which is 7.36% higher than anthracite, the manganese is 93.31%。This new type carburant for increasing the carbon can decrease the temperature of the tapping in the promise of keeping the quality of liquid steel, shorten the logistic time and reduce the cost of steel per ton.

Abstract: The microstructure and element distribution of AZ80 magnesium alloy as-cast and after annealing treatment were studied by OM, SEM, XRD, EDS and TEM. The results show that the coarse divorced eutectic phase distributed along the grain boundary dissolve into Mg matrix during the isothermal process at 415°C for 24h. During the cooling process of annealing treatment, the lameller-shape β-Mg₁₇Al₁₂ nucleated preferentially in the grain near the boundary, then grows towards the neighbor grains with longitudinal direction, which precipitated from magnesium solid solution as perlite-type precipitation. When cooled to room temperature, the lameller-shape β-Mg₁₇Al₁₂ was uniformly distributed in the matrix, and the lamellar spacing inside β phase is about 1-2μm.

Abstract: In this paper, TZS88 aluminum alloy mechanical properties of three months of natural aging is tested, the microstructure and the strengthening mechanism is studied by the application of optical metallographic microscope and scanning electron microscopy. The results show that TZS88 aluminum reinforced mainly caused by solid solution strengthening, aging strengthening and dispersion strengthening, and as such its tensile strength, hardness and elongation in the natural aging have reached ZQSn6-6-3 bronze level, the microstructure are compounds which included α(Al) solid solution matrix + Sn + s, θ, T, ε etc.

Abstract: Cu-0.2wt%Cr-0.5wt%Zr-0.1wt%RE(La) was prepared by casting, quenching, rolling and aging. The microstructure was studied by electron microscope and the texture components were studied by electron backscattered diffraction. In the cast alloy, pure chromium distributed near the grain boundary as a strip shaped and Cu5Zr phase distributed in the interior of grain as a shape of granules. The texture components of the rolled plate include {110} and {112}. With the rolling ratio increased, {112} texture component became the primary rolling texture component. The strengthening effect was attributed to the refinement of the grain size. The electron conductivity was mainly affected by the misorientation of the grain size with a high rolling ratio.

Abstract: During the metal hot working process, the dislocation density will vary with strain and strain rate, and the variation of the dislocation density will affect the grain evolution subsequently. The cellular automaton (CA) method is an effective technique used to simulate the grain evolution of materials. In this work, a dynamic recrystallization (DRX) model of titanium alloy TC11 under varied strain rates was established by the use of cellular automaton method and verified by experimental observation. Two types of loading processes called “begin fast and then slowly” and “begin slowly and then fast” were simulated to investigate the titanium alloy TC11 grain evolution processes during hot working. The simulation results are in good coincidence with experimental data. Both cellular automaton simulation and experimental results show that the flow stresses and DRX transformation percentage during hot working process of the TC11 alloy are closely related not only to the strain rate but also to the loading sequence. Compared to the “begin slowly and then fast” loading sequence, the flow stress with the “begin fast and then slowly” loading sequence is relatively smaller under the same strain rates, and the DRX transformation percentage is relatively larger.

Abstract: The impact toughness of ZA27 alloy at different temperatures is investigated by pendulum impact testing. In addition, the morphology of impact fracture surface observed by SEM. The results indicate that impact energy of ZA27 alloy is reduced with the temperature rising when the temperature is lower than 100°C. At 100°C to 200°C, impact energy increase as the temperature rising. And when the temperature reaches to 250°C, impact energy suddenly descend. Impact energy is the highest and reaches to 72.768J at 20°C. At impact fracture surface, it is mostly tear ridges and dimples. The higher the impact energy is, the more obvious the characteristic of tear ridges is. Furthermore, dimples are small and distribute more uniformly. Lower the impact energy, the less distinct of tear ridges. Dimples are larger and deeper, their distribution are not uniform. Impact behavior of material could be evaluated by the width of impact curve. The wider the peak of impact curve, the higher the impact toughness. But impact toughness is worse while peak is narrow.

Abstract: Microstructure of the Ni-30Al-8Mo-2Nb alloy is dendrite of NiAl, Mo and small amount of Ni3Al phases, the Ni-40Al-8Mo-2Nb alloy is also dendrite of NiAl and Mo phases, and the Ni-50Al-8Mo-2Nb alloy is irregular dendrite of NiAl, Mo and small amount of NiAlNb(laves) phases. Upon the experiment, NiAlNb(laves) phase is only found in the Al-rich alloy. Compressive yield strength of the Ni-40Al-8Mo-2Nb alloy is higher than that of the Ni-30Al-8Mo-2Nb alloy, and much higher at low temperature or fast initial strain rate. TEM observation shows that the high temperature deformation of the Ni-40Al-8Mo-2Nb alloy is controlled by dynamic recovery and dynamic recrystallization.

Abstract: Mg60Ni23.6La16.4 amorphous ribbon was prepared by melting-spinning method and the crystallization behavior was investigated by differential scanning calorimetry (DSC). The Mg60Ni23.6La16.4 crystallization process exhibits two stages of crystallization and shows an obviously kinetic nature. Isothermal DSC curves indicate that the crystallization is a nucleation-and-growth procedure. The activation energy analysis based on Kissinger Method shows that the growth process for the first crystallization procedure is more difficult than that for the second one. Calculation based on the Johnson-Mehl-Avrami (JMA) model shows that the primary crystallization starts from small crystalline grains with an increasing nucleation rate.

Abstract: A method to estimate the thermodynamic properties of Multi- component white gold alloys from those of constitutive binary alloys was proposed. The Miedema's theory and Chou model. were used to calculate the formation enthalpies of Au–Cu–Ag-Zn-RE alloys. The agreement between the calculation and experiment is reasonable. Formation enthalpies of Au–Cu–Ni-Zn-RE and relative stability of their intermetallic compounds were predicted with present method.

Abstract: In this study，a simulation model of deformed microstructure has been proposed on the basis of the initial microstructure obtained from normal grain growth simulation with Monte Carlo method．And simulation models of recrystallization microstructure of heterogeneous and simultaneous nucleation and random growth of nuclei have been developed in terms of the mechanism of microstructure evolution．On the basis of the simulated microstructure parameters distribution obtained by incorporating the neural network model into FEM Code，simulation and visualization of the microstructure of Ti-15-3 alloy during hot compression deformation and solution treatment have been realized．Comparison of the simulated results with the corresponding experimental ones indicates that the size and distribution of the simulated grains agree well with the actual ones．These studies lay scientific foundation for determining reasonable hot forming process．