Alumina–Aluminide Alloys (3A) Technology: I, Model Development

The general reaction behavior of the 3A process under the thermal explosion mode of synthesis has been investigated via a continuum model. The continuum model uses mass and energy balances to predict temperature difference ( T _s,avg− T _f) curves, as well as profile curves of the reactant conversions and sample temperature. In particular, the effect of the dimensionless parameters associated with the rate of local heat generation (β, the thermicity factor), the activation energy (γ, the Arrhenius number), the rate of heat redistribution (α, the modified thermal diffusivity), the rate of heat transfer by convection (Bi, the Biot number or convective heat transfer parameter), and the rate of heat transfer by radiation (Ω, the radiative heat transfer parameter) were investigated. Conditions to control the reaction process, which should produce high-density final products, were determined. It was found that the overall maximum temperature may be reduced for high γ, low β, high α, and high Bi and Ω. In terms of processing conditions, this may be obtained by reducing the initial reactant concentrations, optimizing the particle size, using small sample sizes and high compaction pressure, and increasing the heat loss by using a high thermal conductivity inert gas.     

Coating of TiB2 dispersed Ti50Ni50 superelastic alloy layer onto Ti-6Al-4V alloy by spark and resistance sintering

The spark and resistance sintering (SRS) of a mixture of Ti, Ni, and TiB₂ powders was carried out to form a TiB₂ dispersed TiNi alloy layer onto a Ti-6Al-4V alloy substrate. The strength and delamination resistance of the surface layer were evaluated by three-point bending tests. The results showed that the bending strength of the specimen with the TiNi alloy surface layer without TiB₂ particles sintered at 1273 K was low because the crack initiation occurred at an early stage of loading in a thick interface layer containing brittle Ti-Ti₂Ni eutectic. By decreasing the sintering temperature to 1200 K, the bending strength increased and the crack initiation occurred from the surface because the interface layer was thin and did not contain the brittle Ti-Ti₂Ni eutectic. For the specimens with TiB₂ dispersed TiNi surface layer that was sintered at 1273 K, the bending strength was larger than that of the specimens with TiNi surface layer because the interface layer does not contain the Ti-Ti₂Ni eutectic and compressive residual stress generated in the surface layer during cooling process after SRS suppresses the crack initiation on the surface. The coating of TiB₂ dispersed TiNi alloy onto titanium alloys by SRS provides strong interface to prevent delamination of the surface layer, strong surface due to residual compressive stress, and wear-resistant surface due to the existence of hard TiB₂ particles and superelastic deformation of TiNi matrix.     

覆膜陶瓷粉末烧结过程热应力场研究

研究覆膜陶瓷粉末在选择性激光烧结过程中的热应力场 ,分析烧结过程中各种工艺参数同烧结件质量之间的关系。通过编制相应的程序对其热应力场进行数值模拟 ,从而优化工艺参数 ,确保烧结件质量。     

韶钢烧结厂的技术改造

介绍韶钢烧结厂近年来的技术改造内容，包括上料系统、烧结机主机及抽风系统的改造．通过这些改造使韶钢烧结厂的利用系数和设备日历作业率稳步提高，从而为炼铁的降成本、增效益作出了贡献，并对目前韶钢烧结厂存在的问题及今后的发展提出了设想     

宝钢热废气烧结实验室研究烧结矿矿相分析

在实验室条件下研究了不同热废气温度对宝钢原料条件下烧结矿的产质量的影响，并着重利用矿相分析对结果进行了分析的讨论。     

配加锈化球烧结试验研究

对配加锈化球烧结进行了基准试验和不同配比的系列试验。试验证明 ,混匀料中配加 10 %的锈化球 ,试验的判定指标可达到最佳值 ;锈化球可以取代粗粉保证料层具有良好的透气性 ;实际生产时 ,建议锈化球的粒度须小于 8mm ,其中 1～ 6mm占 80 %以上为佳     

莱钢2×105 m2烧结机系统的改造

介绍了莱钢烧结厂2台105m^2烧结机自投产以来进行的主要设备改进及其效果。     

Kinetic Analysis of Solution-Precipitation During Liquid-Phase Sintering of Alumina

Densification controlled by solution-precipitation during liquid-phase sintering was analyzed for the aluminamagnesium aluminosilicate glass system. As a model system for liquid-phase sintering, narrowly sized alumina powders and up to 20 vol% magnesium aluminosilicate glass samples were isothermally sintered at 1550° to 1650°C. Densification rate increases with increasing liquid content and sintering temperature but decreases with increasing density. For samples with >15% grain growth, the densification rate during the solution-precipitation stage of sintering was proportional to (particle size)⁻² and thus interface reaction-controlled. Activation energies ranged from 270 to 500 kJ/mol over the relative density range of 66% to 96%, respectively. The low activation energy is attributed to densification by particle rearrangement, whereas the higher activation energy is due to densification controlled by interface-reaction-controlled solution-precipitation. Intermediate activation energies are attributed to simultaneous densification by the two mechanisms.     

Stabilization of Cubic Zirconia by Aluminum Nitride

Cubic ZrO₂ is stabilized at room temperature by the addition of AIN. The percentage of c-ZrO₂ in the mixture of c-ZrO₂ and m-ZrO₂ increases linearly with the addition of up to 20 mol% AIN and decreases thereafter. Stabilization becomes complete at 50 mol% AIN. The lattice spacing of the cubic phase gradually expands up to 20 mol% AIN. A displacement reaction ZrO₂+ AIN → ZrN+Al₂O₃ occurs above 20 mol% AIN and is completed at 50 mol% AIN.     

钼粉形貌特征对烧结制品的影响分析

对钼粉生产过程中出现的各种形貌进行了分析，发现钼粉的微观形貌除了常见的均匀球形小颗粒，还有其他片状颗粒、条形团聚体、絮状团聚体；微观形貌的差异导致宏观物理性能不同，通过形貌及其物理性能对后续产品生产可能产生的影响进行了分析、讨论。