全层状TiAl合金层片生长及其影响因素

利用光学显微镜(OM)和TEM，研究了全层状TiAl合金的层片间距的影响因素及与各因素的关系。实验结果表明，全层状TiAl合金的层片间距与冷却速度和合金中铝含量有关，层片间距与冷却速度呈反比关系，并随着合金中铝含量的增加而增加。同时，以层片生长的台阶机制为基础，推导出了全层状TiAl合金在连续冷却过程中层片间距的数学表达式，推导结果与实验结果相符。     

纯铝等径角挤技术（I）——显微组织演化

研究了纯铝在 3种 (A、B和C)不同等径角挤工艺中的显微组织演化。结果表明 :纯铝经过等径角挤压变形后 ,其显微组织特征与加工路线有很大的关系。提出了立方元素扭转模型 ,分析了 3种不同加工路线的剪切面和剪切方向 ,较好地解释了采用 3种不同路线挤压后材料显微组织的演化规律。在路线C(各道次挤压间试样旋转 180°)中 ,每次挤压样品总是在相同的剪切面上发生剪切 ,每相邻道次之间的剪切方向相反 ,前一次变形产生的剪切应变被随后紧接着的下一次挤压所抵消 ,这导致了多余的剪切应变 ;在路线A(各道次挤压间试样不旋转 )中 ,有两个相交成 6 0°的剪切面 ,剪切交替地在两个剪切面上进行 ;在路线B(各道次挤压间试样旋转 90°)中 ,存在 4个不同的剪切面和剪切方向 ,挤压交替地在 4个剪切面上进行 ,X ,Y和Z平面上的晶粒都发生了剪切 ,这有利于等轴晶结构的形成     

Effects of can parameters on canned—forging process of TiAl base alloy（Ⅱ）——Mechanical behavior

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Ti-Al基合金中的Hall-Petch关系及影响因素分析

研究了全层片状组织Ti-Al基合金的室温拉伸性能与品团尺寸的关系。Ti-Al基合金的室温拉伸屈服强度和断裂强度与晶团尺寸成Hall-Petch关系。当合金中添加替代元素Cr和Nb时，其Hall-Petch斜率不变；而添加间隙元素C和B时，其Hall-Petch斜率增加。Ti-Al基合金的室温延伸率与晶团尺寸不满足Hall-Petch关系。     

Electrodeposition of Ni-Co-Fe2O3 composite coatings

Ni-Co-Fe₂O₃ composite coatings were electrodeposited using cetyltrimethylammonium bromide (CTAB)-modified Watt’s nickel bath with Fe₂O₃ particles dispersed in it. The effects of the plating parameters on the chemical composition, structural and morphological characteristics of the electrodeposited Ni-Co-Fe₂O₃ composite coatings were investigated by energy dispersive X-ray (EDS) spectroscopy, X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results reveal that Fe₂O₃ particles can be codeposited in the Ni-Co matrix. The codeposition of Fe₂O₃ particles with Ni-Co is favoured at high Fe₂O₃ particle concentration and medium stirring, and the deposition of Co is favoured at high concentration of CTAB. Moreover, the study of the textural perfection of the deposits reveals that the presence of particles leads to the worsening of the quality of the observed 〈220〉 preferred orientation. Composites with high concentration of embedded particles exhibit a preferred crystal orientation of 〈111〉. The more the embedded Fe₂O₃ particles in the metallic matrix, the smaller the sizes of the crystallite for the composite deposits.     

Electrocatalytic properties of Ni-S-Co coating electrode for hydrogen evolution in alkaline medium

Amorphous Ni-S-Co alloy was prepared by means of chemical electro-deposition method on the foam nickel matrix. The surface morphology and microstructure of Ni-S-Co coatings were studied usmg SEM and XRD, and the electrochemical properties were tested by electrochemical methods. The results show that the coating has amorphous structure and the particles of the surface are fine with large specific surface area. The Ni-S-Co alloy is more active with lower potential for hydrogen evolution, higher exchange current density and lower activation energy compared with Ni and Ni-S electrode. Its hydrogen evolution reaction（HER） is enhanced, the size of particles of surface decreases and the surface area increases after being activated by KOH alkaline solution.     

Charge-discharge process of MnO2 supercapacitor

Mechanochemical synthesis of α-MnO2 was carried out with KMnO4 and Mn（CH3COO）2 in 1：1 mole ratio. The electrochemical performance of MnO2 electrode was investigated by cyclic voltammograms and alternating current impedance. The charge-discharge process of MnO2 supercapacitor in 6 mol/L KOH was studied within 1.2 V at 200 mA/g, suggesting that it displays double-layer capacibility in low potential scope and pseudo-capacitance properties in high potential scope. It is found that Mn3O4, an electrochemical inert, mainly forms in the initial 40 charge-discharge cycles. During cycling, the pseudo-capacitance properties disappear and the discharge curves are close to ideal ones, indicating double-layer capability. The maximum capacitance of MnO2 electrode is as high as 416 F/g, and retains 240 F/g after 200 cycles. The equivalent series resistance increases from 17 to 41Ω.     

HA/Ti composite for biomedical application by mechanical milling

In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti,HA/Ti composites with various compositions were prepared by mechanical milling.The effects of milling condition and the composition on the microstructure,the density and the hardness of the composites were studied.The results show that during the ball milling process.Ti particles are refined and the homogeneity of the HA/Ti mixtures is improved;HA will partially decompose due to the existence of Ti and high sintering temperature.The microstructure of HA/Ti composites is highly dependent on the milling condition and the composition.In the microstructure.Ti phase connects to be a continuous network,and HA/Ti mixtures disperse in the network.The longer the milling time,the finer the network will be.The density of HA/T composites decreases with the content of HA increasing and the milling time prolonging,because HA deteriorates the sinterability of Ti.The hardness of HA/Ti composites increases firstly with the content of HA increasing,and then drops when the content of HA exceeds 30%.Addition of HA will strengthen the HA/T composite but will decrease the density of the composite,which accounts for the effect of HA on the hardness of the composites.     

Performance of positive and negative electrodes in amorphous manganese oxide supercapacitor

Using potassium permanganate and acetic manganese as the reactants, amorphous manganese oxide was prepared with mechanochemical method. XRD was used for microstructure characterization, while cyclic voltammetry and constant current charge-discharge were used for electrochemical performance testing. The positive electrode （PE） and negative electrode （NE） were investigated respectively in amorphous manganese oxide supercapacitor, aiming to find their different performances in charging-discharging. The results show that the crystalline structure is destroyed in both the PE and NE material during charge-discharge process. Thereinto, the NE suffers a bit more seriously. When cycling, the PE potential scope diminishes while the NE potential scope enlarges. The increased inner resistance makes the NE curves almost bended to be a right angle, but not the PE curves. The cell＇s equivalent series resistance （ESR） is more dependent on the NE, and the capacitance is mainly determined by the rapid descent of the NE potential range. The capacitances of the NE are highly rate-dependent, decreasing from 121.3 to 53.1 F/g, by 56.2%, over the range of 5-25 mV/s. However, the PE appears to be weakly dependent and its capacitance is only dropped by 22.1%.     

纯铝等径角挤技术(Ⅱ)--变形行为模拟

通过有限元模拟和坐标网格，对纯铝等径角挤过程的变形行为进行了模拟和试验。结果表明，纯铝在单道次等径角挤压过程中所需的载荷随着样品位移的增加大致可分为快速增加、缓慢增加、快速增加、载荷值趋于稳定、载荷下降5个阶段。由于样品外部在主要变形区的流动速率比样品内部的快，因而样品在等径角挤压过程中会出现不均匀变形，样品底部沿宽度方向的塑性变形量明显少于样品顶部和中部的，坐标网格法实验结果也证明了这一点。在等径角挤压过程中，样品不同部位的应力状态不一致，样品内部存在压应力→拉应力的转变，样品外部存在压应力→拉应力→压应力的转变。摩擦消除后，有效应变有所增加，但并不能降低样品变形的不均匀性；采用尖角模具既能产生更大的剪切应变，又能提高变形的均匀性。