Failure of Zr61Ti2Cu25Al12 bulk metallic glass under torsional loading

The torsional properties of the Zr₆₁Ti₂Cu₂₅Al₁₂ BMG have been tested using cylinder samples, including the shear yield strength, shear elastic strain limit and shear modulus. Under torsional loading, the BMG fails via a major shear band, without obvious macroscopic plasticity on the specimen surface. The shear band maintained stable propagation by a distance of ∼300 μm (∼20% of cylinder radius) before final catastrophic failure, owing to the constraint of stress gradient along the radial direction. The combined tensile, compressive and torsional properties of the Zr₆₁Ti₂Cu₂₅Al₁₂ BMG suggest that recent ellipse criterion and eccentric ellipse criterion are more appropriate than other well-known ones in describing the yield behavior of this BMG. The cooperative shear model underestimates the shear elastic strain limit, because of its default assumption that the yielding behavior follows the Tresca yield criterion.     

Heating characterization of the thickness-through fatigue crack in metal plate using sonic IR imaging

In sonic IR imaging, a major problem is exploring the heating characteristics of crack vicinity to guide the optimization of the test conditions. In this paper, the crack's heating characteristics of the metallic plate with an artificial fatigue crack has been studied. Experimental results showed that the during ultrasonic excitation the temperature rise of crack vicinity at the plate's excitation side is higher than that at its opposite side, whereas the total heating efficiency of the crack face appears to be stable. Through the profile mapping of the crack face, the frictional heating is mainly concentrated near the excitation side. Based on this phenomenon, we built a mathematical heat transfer model to calculate the temperature distribution of the crack vicinity and investigated the heating features of crack faces. Additionally, the mathematical model gives a quantitative relation between the depth of the heat source and the ratio of the temperature distribution of the crack vicinity at opposite side to that at the front side. This study aims to provide a quantitative evaluation method for locating the frictional heating areas in sonic IR imaging.     

Micropatterning of Ni-based metallic glass by pulsed wire electrochemical micro machining

The technique of wire electrochemical micro machining (WECMM) is proposed firstly for the micropatterning of Ni-based metallic glass in this paper. Metallic glass (MG) exhibits many outstanding properties such as high hardness and strength, which enable it to be used as functional and structural materials in micro electromechanical systems (MEMS). A significant limitation to the application of MGs is the challenge of shaping them on micro scale. WECMM is a non-traditional machining technique to fabricate microstructures that has some unique advantages over other methods, which will be a promising technique for micro shaping of metallic glass structures. Taking the example of a Ni-based glassy alloy, Ni₇₂Cr₁₉Si₇B₂, the polarization and fabrication characteristic in dilute hydrochloric acid electrolyte were investigated. Changes in the machined slit width in terms of several experimental parameters were investigated to find the optimal ones. Finally, the optimal machining parameters: HCl electrolyte concentration of 0.1 M, applied voltage of 4.5 V, pulse duration of 80 ns, pulse period of 3 μs and feed rate of 0.3 μm s⁻¹ were employed for the fabrication of microstructures. Such as a micro square helix with a slit width of 14.0 μm, standard deviation of 0.2 μm and total length up to 2000 μm, along with a micro pentagram structure with side length of 90 μm and sharp corner of 36°, were machined with a high level of stability and accuracy.     

金属腐蚀性能导数预测方法

工程中金属材料腐蚀性能的预测具有十分重要的意义,但是长期腐蚀性能预测的精度问题始终未能得到很好解决。文中提出一种金属腐蚀性能导数预测方法,建立新的三参数指数函数预测模型。该方法首先对原始腐蚀试验数据进行加权累加变换,使其最大限度呈现出指数函数规律,然后采用三参数指数函数预测模型描述加权累加后数据的变化规律,并通过导数最小二乘法确定模型中的待定参数。从而能够同时对腐蚀性能曲线及其导数进行拟合,很好把握腐蚀性能曲线的变化趋势,实现对金属长期腐蚀性能的高精度预测、大量对比试验结果表明,与传统方法相比,可以大大提高预测精度．文中给出两个实例。     

几种无铅汽油抗爆剂作用机理及工业应用

叙述了金属汽油抗爆剂和非金属汽油抗爆剂的抗爆震机理,介绍了ＭＭＴ,ＴＫＣ、ＡＲＤ－Ｊ、ＦＡ－９０四种抗爆剂的辛烷值感受性工业试验结果。     

提高硅烷试剂溶液稳定性的研究

硅烷试剂（SA）在金属防腐蚀和提高表面外涂层附着方面的应用是一崭新应用领域，本工作研究了该技术工业化的关键问题之一SA溶液的稳定性，针对提高稳定性的外加试剂进行了探讨；通过对溶液状态和电导率及其它一些相关参数与稳定时间关系的研究，得出可有效提高SA稳定性的添加剂，同时由相应的工艺试验，检验在这些影响因素下稳定性对硅烷膜的耐蚀性及再处理能力的影响。     

Sn对ZrTiNiCuAl非晶合金玻璃形成能力的影响

研究了固溶元素Sn掺杂对Zr52.5Ti5Ni14.6Cu17.9Al10非晶合金玻璃形成能力（GFA）的影响，结果发现，掺杂不同含量的Sn会使玻璃化温度Tg,晶化温度Tx不同程度地向高温移动，但对合金熔化温度Tm温度不大。当Sn的摩尔分数为1．86％时，合金玻璃化温度Tg提高了17℃，晶化温度Tx提高了36℃，从而使△Tx提高了19℃，玻璃化温度与合金熔点温度的比值Trg由0.63提高到0.65分析了Sn元素对Tg,Tx及玻璃形成能力的影响。     

半固态金属铸造的新进展——注射成形

介绍了半固态金属铸造的最新发展趋势———注射成形 ,它将塑料的注射成形原理应用于半固态金属铸造中 ,集半固态金属浆料的制备、输送、成形等过程于一体 ,较好地解决了半固态金属浆料的保存输送和成形控制等问题。通过简述几种半固态金属注射成形工艺方法的原理及特点 ,试图展示半固态金属铸造技术工程应用的关键及发展方向     

MO对B2O3-Al2O3-SiO2系统玻璃析晶性能的影响

研究了添加BaO、CaO、MgO对B2O3-Al2O3-SiO2系统玻璃析晶性能的影响。用DSC测试了玻璃的析晶温度，用XRD分析了玻璃析晶后的晶相组成，用SEM观察了析出晶粒的形貌特征。结果表明：BaO、CaO均可有效促进BAS玻璃的形成，而MgO易导致玻璃分相。MO-BAS玻璃的析晶温度在770～810℃之间。添加BaO时析出的主晶相为硼酸铝（Al18B4O33）和少量勃来石（Al16B6Si2O37），以针柱状晶为主。用CaO替代BaO，析出的主晶相不变，但析晶能力增加，以细小的粒状晶为主。添加MgO时析出的主晶相为偏硼酸铝（Al4B2O9）和勃来石，晶粒较粗大。     

Interfacial Structures Governed Plastic Deformation Behaviors in Metallic Multilayers

In this work, we have investigated the mechanical properties of Cu/Ta, Ag/Cu and Ag/Nb multilayers with different heterogeneous interfaces. The results suggest that when individual layer thickness(h) is larger than 5–10 nm, the hardness/strength of three different multilayer systems has the similar length scale effect with decreasing layer thickness,while when h B 5 nm, the three multilayer systems show remarkably different plastic deformation behaviors. The strength curves exhibit the variation trends of unchanging, softening and increasing corresponding to Cu/Ta, Ag/Cu and Ag/Nb multilayers, respectively. The microstructure analysis shows that three kinds of multilayers have totally different interfacial structures, which lead to the different strengthening or softening mechanisms.