掺杂MgAl2O4的Al2O3陶瓷材料研究

将MgO以MgAl2O4的形式掺杂到Al2O3中,研究MgAl2O4的掺杂量及其在不同烧结工艺条件下,对Al2O3陶瓷烧结性能和显微结构的影响.结果显示在氧化气氛1 640℃下烧结,掺杂MgAl2O4的Al2O3陶瓷烧结性能较掺杂MgO的Al2O3陶瓷差.而在氢气氛1 640℃下烧结,掺杂MgAl2O4的Al2O3陶瓷烧结性能优于掺杂MgO的Al2O3陶瓷,Al2O3陶瓷的相对密度可达99.1%,但晶粒尺寸分布不均匀,在3 μm～7 μm之间.当采用先在氧化气氛1 450℃下一次烧结后,再在氢气氛1 640℃下进行二次烧结时,发现不仅可以获得致密掺杂MgAl2O4的Al2O3陶瓷材料,而且还可以制备出存在大量长柱状晶粒的Al2O3陶瓷.     

烧结助剂Y2O3和Pr6O11对Al2O3陶瓷相对密度和热导率的影响

采用高分子网络法制备混合纳米粉体,研究稀土氧化物Y2O3和Pr6O11加入量对Al2O3陶瓷相对密度和热导率的影响。采用阿基米德方法测定样品的体积密度,利用激光脉冲法测量试样的热扩散率并计算得出热导率。结果表明:两种添加剂都可以降低Al2O3陶瓷的烧结温度,提高Al2O3陶瓷的热导率,其中Y2O3的促进作用较强;当保温时间相同、烧结温度为1 500~1 650℃时,Al2O3陶瓷的相对密度和热导率都随烧结温度的升高而增大;当烧结温度相同、保温时间为30~120 min时,Al2O3陶瓷的相对密度和热导率也随保温时间的延长而增大。     

TiB2含量和烧结温度对B4C/Al2O3基复合陶瓷的影响

利用原位反应热压工艺制备了B4C/Al2O3基复合陶瓷,研究了TiB2含量和烧结温度对B4C/Al2O3基复合陶瓷力学性能和微观结构的影响.结果表明,当TiB2含量低于8.7％时,随原位反应生成的TiB2含量的增加,有效的促进了B4C/Al2O3/TiB2复合陶瓷的烧结,提高相对密度,改善了力学性能.当烧结温度低于1900℃时,其力学性能随烧结温度增加而提高;当超过1900℃时,其力学性能随烧结温度的提高而降低.在1900℃,60 min时,B4C/Al2O3/TiB2复合陶瓷获得最佳综合力学性能,其硬度、断裂韧性和抗弯强度分别为24.8 GPa、4.82 MPa·m1/2和445.2 MPa.     

晶粒尺寸对Al_2O_3/LiTaO_3复合陶瓷中电畴结构的影响

用氮气保护热压烧结工艺制备了Al2O3/LiTaO3复合陶瓷,研究了第二相Al2O3和基体LiTaO3的晶粒尺寸对Al2O3/LiTaO3复合陶瓷中电畴结构的影响.结果表明,Al2O3和LiTaO3的晶粒尺寸变小后,Al2O3/LiTaO3复合陶瓷电畴数量和密度明显变少,而且畴区也较大,只有在晶粒变形较大的地方才会出现典型的非180°电畴结构,但复合陶瓷中电畴结构类型、形貌没有变化.     

Fe3Ai纳米粒子增强A12O3陶瓷的制备及性能

用热压烧结法制备了纳米Fe3Al粒子增强Al2O3基复合材料.研究了1 450～1 600 ℃不同烧结温度下纳米Fe3Al的加入量与材料的致密度、力学性能及显微结构的关系.结果表明纳米Fe3Al的加入可使Al2O3晶粒的生长受到抑制, 使复合材料的烧结温度提高.Fe3Al/Al2O3纳米复合材料有良好的力学性能, 其抗弯强度最高可达832 MPa, 断裂韧性最高可达7.96 MPa*m1/2.     

热压烧结工艺对超韧Al2O3-TiC-Co复合陶瓷性能的影响

热压烧结化学镀法获得的Al2O3-Co TiC-Co复合粉体制备超韧Al2O3-TiC-Co复合陶瓷.探讨了烧结温度、烧结气氛和分级保温时间对复合陶瓷微观形貌和力学性能的影响.结果表明,烧结温度为1550℃、真空保护并在750℃和1200℃各保温10 min制备的复合陶瓷力学性能最佳.采用最佳烧结工艺制备的Al2O3-TiC-8%Co复合陶瓷的平均抗弯强度和断裂韧性分别达到782MPa和8.0 MPa·m1/2.     

ZrB2在Al2O3-ZrB2复相陶瓷中的增韧性能

常压烧结制备了Al2O3和20wt%ZrB2/Al2O3复合陶瓷,用XRD和金相显微镜、SEM分析了其相组成、微观结构、断裂形貌,并用压痕法计算了陶瓷的断裂韧性。结果表明：Al2O3陶瓷自1500℃开始其相对密度超过99%,维氏硬度达到1897HV,断裂韧性为5.2?.3MNm-3/2;20wt%ZrB2/Al2O3复合陶瓷在1450℃时相对密度超过98%,维氏硬度达到1807HV,断裂韧性为6.7?.2MNm-3/2。微观形貌观察表明,ZrB2/Al2O3复合陶瓷韧性的增加是由于弥散分布的ZrB2在Al2O3陶瓷基体中起到遏制裂纹扩展和钉扎双重作用的结果。     

纳米SiC和添加剂ZrO2对Al2O3基纳米复合陶瓷显微组织和性能的影响

采用极性分散剂,在微米Al2O3基体中加入微米ZrO2和纳米SiC颗粒,用真空热压法制备出了Al2O3/SiC纳米复合陶瓷,并研究了微米ZrO2和纳米SiC的添加对Al2O3/SiC纳米复合陶瓷显微组织及其性能的影响.结果表明:与纯Al2O3比较,适量微米ZrO2和纳米SiC颗粒的加入阻碍了Al2O3晶粒的长大,使复合陶瓷的显微组织非常细小,纳米复合陶瓷烧结后的力学性能大大提高.     

Fe3Al纳米粒子增强Al2O3陶瓷的制备及性能

用热压烧结法制备了纳米Fe3 Al粒子增强Al2 O3 基复合材料。研究了 14 5 0～ 16 0 0℃不同烧结温度下纳米Fe3 Al的加入量与材料的致密度、力学性能及显微结构的关系。结果表明 :纳米Fe3 Al的加入可使Al2 O3 晶粒的生长受到抑制 ,使复合材料的烧结温度提高。Fe3 Al/Al2 O3 纳米复合材料有良好的力学性能 ,其抗弯强度最高可达832MPa ,断裂韧性最高可达 7.96MPa·m1/ 2 。     

Al2O3,CaO对多元掺杂YSZ电解质材料性能的影响

采用高温固溶法制备了Dy2O3,Sc2O3和Yb2O3多元掺杂YSZ材料,试样高温电导率得到大幅度提高(1000℃,0.18S/cm),但材料烧结性与机械强度有待改善.为此,在多元掺杂YSZ材料中继续掺入少量Al2O3和/或CaO以研究其影响.添加少量Al2O3提高了试样烧结密度( ～4.6%)和机械强度(～30%),而保持电导率变化不大;添加少量CaO虽然使烧结密度略微增大,但却降低了试样电导率(～50%)和机械强度.XRD分析显示试样保持稳定立方萤石结构,且晶格常数发生变化.显微结构分析表明,复合添加剂的掺入促进了晶粒的生长,晶粒尺寸较大.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

THERMODYNAMICS STUDY ON THE DECOMPOSITION OF CHROMITE WITH KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

INFLUENCE OF HEAT TREATMENT ON DAMPING BEHAVIOUR OF THE MAGNESIUM WROUGHT ALLOY AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.