铝热快速凝固工艺合成高强TiC/FeNiCr复合材料

采用铝热快速凝固工艺制备了FeNiCr合金及TiC／FeNiCr复合材料,利用光学显微镜、扫描电镜、X射线衍射等手段研究了该复合材料的显微组织和相结构,测量了复合材料的压缩强度。结果表明,TiC／FeNiCr复合材料由TiC陶瓷增强相和α-Fe合金基体组成。TiC／FeNiCr复合材料组织细小,TiC呈多边形均匀分布在合金基体中,晶粒尺寸约为2-3μm。TiC对FeNiCr基体具有很好的晶粒细化及强化作用,TiC／FeNiCr的压缩断裂强度及形变率分别为2 760MPa及25％,远大于FeNiCr合金及部分Fe基非晶材料。     

基于DSP320F2812的数字化CO2焊机研制

设计了数字化CO2焊机的硬件结构,并根据CO2焊接工艺的特点,编写了相应的控制软件,实现了整个焊接系统的数字化.试验结果表明,基于DSP320F2812芯片控制的焊接电源具有良好的动特性,获得了较好的控制效果,为控制策略的智能化和最优化提供了良好的平台.     

Oxidation Behavior of a Single-Crystal Ni-Base Superalloy in Air—II: At 1000, 1100, and 1150°C

The oxidation behavior of a single-crystal (SC) Ni-base superalloy was studied over the temperature range from 1000–1150°C and analysed by TGA, XRD, EDAX, and SEM. The results indicated that the SC Ni-base superalloy exhibited parabolic oxidation kinetics, which were controlled by the growth of the inner -Al₂O₃ layer. A mixed scale formed on the SC Ni-base superalloy after prolonged oxidation. The scale consisted of an outer layer of spinel, a sublayer of mainly -Al₂O₃ with small amount of spinel adjoined by a very thin and even discontinuous layer of CrTaO₄-rich oxide, and an inner -Al₂O₃ layer. The inner -Al₂O₃ layer provided good protection. No internal oxides or nitrides were observed below the inner -Al₂O₃ layer after 1000 hr at 1000°C, and after 200 hr at 1100 and 1150°C.     

稀土La对Al-Si合金复合材料凝固组织与溶质偏析的影响

利用挤压铸造法制备了Al2O3/Al-Si-La复合材料;研究了稀土La对复合材料凝固组织以及基体合金凝固时溶质偏析的影响。结果表明,稀土La可细化基体合金的凝固组织,La富集在界面附近,有利于改善铝合金液对氧化铝短纤维的润湿性,但是未发现任何富稀土相在界面上形成。稀土La对基体合金中镁的偏聚没有明显的影响,镁和稀土La均在界面处富集,且它们的分布位置大致近似。     

高铁三水铝石型铝土矿的烧结特性

以Al2O3含量为26.35%,总Fe含量为31.22%,铝硅比为3.17的某高铁三水铝石型铝土矿为原料,研究了碱度、焦粉用量、混合料水分等对烧结矿质量指标的影响。结果表明:烧结矿碱度增加时,其转鼓强度和成品率下降,烧结矿自粉化程度加重;焦粉用量增加时,烧结矿转鼓强度和成品率提高;当混合料水分为9.0%、焦粉用量为8.0%、烧结矿碱度为4时,烧结矿转鼓强度为69.1%,成品率为81.2%,垂直烧结速度为30 mm/min,利用系数为1.2 t/(h.m2);烧结矿碱度为4时,样品存放2天粉化率为5%,烧结矿平均粒度由22.2 mm减小到21.9 mm,延长存放时间,烧结矿自粉化率增大,平均粒度显著减小。该烧结矿的冶金性能能基本满足高炉冶炼的要求。     

Conductivity enhancement in transparetn ZnO films via Al-dopping produced by CW-CO2 laser-induced evaporation

Highly conductive transparent aluminium-doped ZnO (ZnO:A1) films were successfully deposited by CW-CO₂ laser-induced evaporation. Optimisation of evaporation parameters was based on laser power, substrate temperature, O₂ partial pressure in the vacuum chamber and amount of Al in the ZnO source pellet. ZnO:A1 films with an electrical resistivity as low as 6.6 × 10⁻²Ω·cm and an optical transmission of 80% at 500nm were obtained at laser power of 15 W, substrate temperature of about 200°C, O₂ partial pressure of 6—7 × 10⁻⁴ Torr and 5wt.% Al. Conductivity of ZnO films can be increased one order via Al-doping in ZnO films. The films obtained by laser-induced evaporation have compared quite favorably with the high quality films obtained by sputtering.     

Tool wear and chatter detection using the coherence function of two crossed accelerations

Tool wear and chatter have been found to be the main causes of rejects in the machining of super alloys. A novel detection technique to identify both tool wear and chatter in turning a nickel-based super alloy is introduced. It uses the coherence function between two crossed accelerations from the bending vibration of the tool shank. The value of the coherence function at the chatter frequency reaches unity at the onset of chatter. Its values at the first natural frequencies of the tool shank approach unity in the severe tool wear stage. The results are interpreted using the analysis of the coherence function for a single input-two output model. The advantage of using this method is that the thresholds for detecting severe tool wear and chatter can be easily set, since values of coherence function are normalized to a range of between zero and unity, and are also not so susceptible to changing cutting conditions, because the value of the coherence function is close to unity at the onset of chatter and severe tool wear.     

HOMOGENIZATION TREATMENT OF Mg-Al-Zn(MM)MAGNESIUM ALLOY INGOTS

The Mg-Al-Zn series AZ31 and AZ31 MM alloys are homogenized at 673, 723 and 753K respectively. The hardness of alloy ingots at different heat-treated states is measured and the micro structures are observed. The optimum annealing temperature is 723K and the time is 12h.     

低压铸造凝固模拟中时间步长的实用算法

针对低压铸造凝固模拟计算过程中存在的收敛性问题，提出了一种能够处理复杂边界条件的简单算法，准确地给出了临界时间步长，避免了计算发散的现象，同时减少了计算的工作量。     

快速低温固体S—C—N三元共渗工艺研究

以木炭、尿素和硫化铁为渗剂,用稀土化合物CeCl_3作催渗剂,于570℃进行固体S-C-N三元共渗。试验结果表明,在相同时间内加催渗剂的渗层深度比不加催渗剂的有大幅度提高,且硬度及耐磨性亦有较大提高,硬度梯度较平缓。离子探针分析表明,稀土元素Ce亦被渗入钢的表面,它不仅起到活化渗剂的作用,同时在提高钢的性能方面还起到微合金化的作用。