温度和加载速率对位错发射影响的原子级模拟

以Ａｌ为研究对象，采用ＥＡＭ势实施分子动力学模拟，在Ｉ型和Ⅱ型加载条件下，研究了温度和取向对位错发射，裂纹脆性及韧性扩展的影响，模拟结果表明，升高温度计等发射位的临界应力强度因子按指数规律降低，加载国速度在一定范围内将影响临界应力强度因子，临界应力强度因子随着加载速度的增大而增大。     

BaAl12O19高温热稳定材料制备方法

ＢａＡｌ１２Ｏ１９是一种被用于高温催化燃烧的β－Ａｌ２Ｏ３型材料．在其制备过程中可采用柠檬酸盐无定形前驱体法．它在１３０℃的分解反映出硝酸盐与自由羰基的相互作用；３６０℃的分解对应于柠檬酸盐的氧化；在８００℃时，ＢａＣＯ３分解并生成ＢａＡｌ２Ｏ４．ＢａＡｌ２Ｏ４的产生并没有抑制ＢａＡｌ１２Ｏ１９的形成．形成ＢａＡｌ１２Ｏ１９的另一条途径是γ－Ａｌ２Ｏ３同分散相Ｂａ２＋之间的反应     

强化冷却下正交切削Ti6Al4V合金的有限元分析

为正确分析切削介质的强化冷却对金属切削过程的影响，应用通用商业有限元软件Deform-2D，对航空用钛合金Ti6Al4V进行了强化冷却条件下的正交切削有限元模拟．通过几何建模、网格划分、边界条件的设定以及材料本构模型的选取等，模拟了Ti6Al4V合金锯齿状切屑的形成过程；文中还分析和探讨了不同强化冷却条件下的切屑形成、切削力以及切削温度的变化．结果表明：随着换热系数的增大，刀具前刀面的平均温度逐渐减小，而换热系数的高低对切削力及前刀面最高切削温度的变化无显著影响．     

莫来石结合铝锆质耐火浇注料及制品

超细粉结合超低水泥耐火浇注料，具有良好高温性能，成本较低，但抗热震性能不理想．莫来石结合锆刚玉浇注料含有较多ZrO2(30％以上)，耐高温抗热震，抗蚀性能优良，但其成本高，除特殊情况外，难于大批量推广应用，耐火浇注料(Al2O3)中引入少量ZrO2可以大幅度改善耐火浇注料抗热震性能，且成本增幅不大。     

粉末冶金Al-10%Ti复合材料的力学和耐磨性能

文章采用“冷压烧结+热挤压”的粉末冶金法制备出Al—10％Ti复合材料,研究了Al—10％Ti复合材料的孔隙率、抗拉强度、伸长率、硬度和耐磨行为。结果表明:与Al相比,Al-10％Ti复合材料的孔隙率较高,抗拉强度和伸长率较低,硬度和耐磨性较高;Al-10％Ti复合材料的磨损体积损失分别是Al的1/22.3及Qsn6.5-0.4的1/14.8,其磨损表面呈Al基体+Ti颗粒+孔隙的耐磨组织。     

原位颗粒含量对半固态7075铝合金组织的影响

制备具有不同原位TiC颗粒含量的喷射沉积7075铝合金,在610℃和620℃进行二次加热并保温30min,淬火固定半固态组织.采用扫描电镜观察其组织,利用平均截线法统计其晶粒尺寸,分析不同颗粒含量对喷射沉积7075铝合金半固态组织的影响规律.结果表明:当TiC颗粒含量达到2.91%(体积分数)时已经产生良好的钉扎效果,使得合金基本保持喷射沉积组织特征,能够满足后续的半固态成形工艺要求;TiC颗粒含量超过2.91%后,晶粒尺寸会进一步减小,但晶界上的颗粒明显增多并呈网状分布;TiC颗粒含量小于2.91%时,局部区域发生晶粒的异常长大现象,使合金组织的均匀化程度下降.     

Atomic-scale computer simulation for early precipitation process of Ni75Al10V15 alloy

The kinetic model for a ternary system is introduced based on the microscopic diffusion form of the phase-field equations for a binary alloy. The equation is solved in the reciprocal space. This model is used to investigate the early precipitation process of Ni75-Al10V15 by simulating the atomic pictures of the two ordered phases and calculating the order parameters of γ′(Ni3Al) phase. Simulation results show that the γ′ ordered phases precipitate from the disordered matrix by a non-classical nucleation mechanism, and the nonstoichiometric γ′ ordered phase appears first and then transforms into the stoichiometric one. Clusters of V atoms appear at the γ′ phase boundaries followed by the formation of the nonstoichiometric θ ordered phase. The farther the location from γ′ phase boundary is, the lower the order degree of θ phase is. There exist two kinds of DO22 ordered domains: a horizontal one and a vertical one, related to their adjacent γ′ phase boundaries. The model could describe the atomic ordering and composition clustering simultaneously, and any a priori assumption about the new phase structure and precipitation mechanism etc. is unnecessary.     

Computer simulation for the precipitation process of Ni75Al7.5V17.5 alloy

The precipitation mechanism of Ni75Al7.5V17.5 alloy above the L12 instability line, between the L12 and D022 instability lines and below the D022 instability line are studied using microscopic phase-field kinetic equation. This paper is aimed at investigating the effect of temperature on precipitation mechanism and morphological evolution of the alloy. Our simulations demonstrate that the precipitation is a mixed mechanism of non-classical nucleation growth and spinodal decomposition above the L12 instability line. It needs certain thermal fluctuations for nucleation and the number of θ phases is small at this temperature. The precipitation mechanism of γ'phase is congruent ordering followed by spinodal decomposition, and θ phase is a mixed mechanism of non-classical nucleation growth and spinodal decomposition between the L12 and D022 instability lines. The mechanism below the D022 instability line is similar to that between the L12 and D022 instability lines. With the decrease of the temperature, ordering and phase separation becomes fast, the dimension of γ'phase becomes small, the shape transforms from equiaxed to block, the dimension of θ phase becomes large and the shape transforms from strip to circle.     

Effects of Ca on the distribution, structure and morphology of aluminum species in polyaluminum chloride

The flocculation efficiency of polyaluminum chloride (PAC) is closely related to the distribution and structure of its AI species, and Al13 is the optimal species in PAC for flocculation. A series of PAC containing Ca was prepared by adding Ca before and after the basifying reaction. The effects of Ca on the Al species were studied by ^27Al nuclear magnetic resonance (NMR) and atomic force microscope (AFM) techniques. The experimental results show that the introduction of Ca increases the content of Alm and Al13 in PAC and decreases their chemical shifts in NMR spectra due to the electric repulsion between the positive Ca species and AI species and the formation of AI-O-Ca complexes.With the rise of Ca/AI molar ratio, the AI species in PAC tend to scatter. It is observed that the formerly branch-aggregated clusters are tending to form granule-aggregated ones whose diameter gets smaller and smaller, and the floccule aggregates are formed at a higher Ca/Al molar ratio. The introduction of Ca to PAC, which increases the Al13 content, is certainly to enhance the flocculation efficiency of PAC in water treatment.     

多层喷射沉积制备耐热铝合金管坯热流分析(Ⅱ) --沉积过程热流分析

通过建立沉积阶段热流分析模型，对多层喷射沉积制备耐热铝合金管坯过程中喷射流沉积后的凝固和冷却进行了分析．喷射流沉积后与基体／沉积坯的传导热交换占热输出率的90％以上，在沉积过程中，沉积面的温度变化呈周期性的升降．计算结果表明，多层喷射沉积采用移动坩埚式扫描方式，延长了喷射流沉积时间间隔，喷射流沉积后可以获得10^3K／s以上的冷却速度。