Sustainable end-of-life vehicle recycling: R&;D collaboration between industry and the U.S. DOE

Approximately 15 million cars and trucks reach the end of their useful life in the United States each year. More than 75% of the materials from end-of-life vehicles are profitably recovered and recycled by the private sector; automotive materials recycling is a success story. To achieve greater fuel efficiency and safety, today’s cars incorporate an increasing share of innovative light-weight materials. While these materials greatly enhance efficiency during vehicle use, they can present special challenges for recycling. These challenges will persist as automotive designs and the mix of materials used in vehicles continue evolving to further improve safety and performance. To meet the challenges of automotive materials recycling, the U.S. Department of Energy has recently expanded its collaborative research with industry in this area. This article discusses this collaborative government/industry approach to sustainable end-of-life vehicle recycling. For more information, contact Edward J. Daniels, Argonne National Laboratory, 9700 S. Cass Avenue, Building 362, Room C393, Argonne, IL 60439-4815; (630) 252-5279; fax (630) 252-1342; e-mail edaniels@anl.gov.     

Microstructure and properties of TiB/Ti-6Al-4V coatings produced with laser treatments

TiB/Ti-6Al-4V metal-matrix composite (MMC) layers were produced on Ti-6Al-4V substrates by laser cladding. A TiB₂/Ti powder mixture was used as a precursor to obtain a dispersion of TiB needles in the Ti alloy matrix, with the aid of an exothermic reaction between TiB₂ and Ti. A eutectic microstructure was obtained that consisted of an extremely homogeneous dispersion of TiB eutectic needles in the Ti alloy matrix, having a volume fraction as high as 0.33. Also, an equilibrium-like microstructure was found, consisting of a dispersion of both primary and eutectic TiB needles inside the Ti alloy matrix. An analysis of the geometry of the layers was performed and proved successful in determining the percentage of B. Further, it correctly predicted the variation of atomic B content as a function of laser power. The relative wear resistance coefficient, defined as the wear coefficient of the uncoated matrix divided by that of coating, shows an improvement by a factor as high as 1500 for the eutectic microstructure. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appeared on pp. 411–18 of the Proceedings.     

The real-time,high-resolution x-ray video microscopy of solidification in aluminum alloys

The directional solidification of thin alloy sheets in a Bridgman furnace has been studied by x-radiography using high-brilliance synchrotron x-radiation in combination with a low-noise, fast-readout camera. Spatial resolutions down to 1.5 μm and a temporal resolution of about 0.15 s have permitted real-time video microscopy of microstructural evolution during columnar and equiaxed dendrite growth and eutectic and monotectic growth. The technique has also allowed for direct observations of important solidification phenomena such as dendrite fragmentation and porosity formation, primarily in aluminium alloys. As a result, insights have been gained into mechanisms of dendrite fragmentation, criteria for dendrite tip kinetics and interface stability during transient growth, and microstructure formation mechanisms during monotectic solidification. The results are expected to be important for validation of dendrite growth models. This paper presents a review of the technique as well as examples of images obtained during solidification of aluminum alloys.     

Effect of joint design on mechanical properties of AL7075 weldment

The effects of joint design on the mechanical properties of AL7075-T6 aluminum sheet were studied on the latest automated gas-tungsten arc-welding system. Using ER5356 filler metal, full-penetration welds were made on workpieces with various included joint angles. Testing of the mechanical properties of the joints was done in the as-welded, naturally aged, and postweld heat-treated conditions. The results show that by using crack-resistant filler, and by selecting the proper joint design and postweld heat treatment, strong, dependable welds can be produced on thin AL7075 sheet material. An elasticity model of the weld joint was established to help understand the mechanical behavior of the joints. An undermatched joint design is shown to be capable of achieving a joint strength that matches the strength of the base alloy.     

基于PAGM模型的浇注系统对螺旋桨铸件夹渣率的影响

基于分散相粒子运动模型,考虑夹渣在随流运动过程中动态聚合长大现象,构建了夹渣聚合长大模型(PAGM,Particles Aggregation Growth Model)。采用PAGM对铝合金螺旋桨铸件浇注过程中夹渣的运动轨迹、聚合长大行为及最终位置进行了模拟计算和试验验证。在此基础上研究了浇注系统对铸件夹渣分布及夹渣率的影响。结果表明,浇注系统设计对夹渣运动行为及分布有较大影响,PAGM可有效提升对铸件夹渣分布预测的准确性,为铸件优化设计及失效分析提供参考。     

Electrochemical analysis of the microbiologically influenced corrosion of steels by sulfate-reducing bacteria

The differences between the general corrosion and microbiologically influenced corrosion (MIC) of steels were investigated in terms of its electrochemical behavior and surface phenomena. The corrosion potential of steels in the absence of SRB (sulfate-reducing bacteria) shifted to a negative value with the immersion time. However, the potential of the presence of SRB shifted to a positive value after 30 days' incubation, indicating the growth of SRB biofilms on the test metal specimens and the formation of corrosion products. In addition, the color of a medium inoculated with SRB changed from gray to black. The change in color appeared to be caused by the formation of pyrites (FeS) as a corrosion product, while no significant change in color was observed in a medium without SRB inoculation. Moreover, corrosion rates of various steels tested for MIC were higher compared to those of steels in the absence of SRB. In particular, the corrosion current density of TMCP steels in the presence of SRB was larger than that of other steels. Pitting corrosion was also observed at the surface of all steels in the SRB-inoculated medium. The pitting corrosion likely occurred due to SRB that was associated with the increasing corrosion rates through increasing cathodic reactions, which caused a reduction of sulfate to sulfide as well as the formation of an oxygen concentration cell.     

Discharge characteristics of lead dioxide electrode prepared with cementation lead oxide

Lead acid batteries have had restricted applications because of relatively low energy density below 50Wh/kg. Many efforts have achieved lighter battery components such as separators, connections and containers etc. Thus, the most important problem of the lead acid battery is to improve the low capacity of the active material in the positive electrode. The purpose of this study is to improve the utilization of the active material in the lead dioxide electrode for the lead acid battery through the production of lead oxide with better physicochemical characteristics through cementation. A cementation reaction was performed in 1.0wt.%HCl solution using pure magnesium plate as the reductant. We investigated the utilization of the active material and discharge characteristics of the positive electrode with a current density ranging from 3.4 to 108.8mAcm⁻². As a result, the active material utilization was about 72% at 3.48 mAcm⁻² and increased with decreasing current density. The discharge characteristics according to current density are especially very good at high current density     

Durability of Titanium/Dicalcium Silicate Composite Coatings in Simulated Body Fluid

Titanium/dicalcium silicate composite coatings with different ratios (weight ratios as Ca₂SiO₄: Ti = 3:7, 5:5, 7:3) were prepared by plasma spraying. Effects of titanium addition on coating properties, such as bonding strength, flexural modulus, and dissolution in simulated physiological environment, were studied. Results showed that the bonding strength between coating and Ti-6Al-4V substrate increased with increase of titanium content in the composite coatings. It was explained by the narrowed dissimilarity of thermal expansion coefficients between the coatings and substrates. Degradation of mechanical properties after immersion in simulated body fluid was also studied. The dissolution of dicalcium silicate in the composite coatings resulted in the decrease of flexural strength and flexural modulus of the coatings in the simulated physiological environment. The higher titanium content in the composite coatings, the stabler are the composite coatings in the physiological environment.     

水压节流阀口流量特性的实验研究及水压节流阀的研制

本文将介绍作者自行研制的水压阀阀口流动特性的实验装置，用该装置完成了各种典型水压阀阀口流动特性以及空化影响流动特性的实验研究，依据实验的结果完成了水压元件性能试验台所需各类水压阀的研制。     

碳化钨钢结硬质合金渗硼层热疲劳特性的研究

本文对GJW50碳化钨钢结硬质含金进行了粉末渗硼处理，在自约束型热疲劳试验机上进行了25－680℃的效疲劳试验．用光学显微镜和扫描电镜观察了在突变热应力的作用下，热疲劳裂纹在渗硼层萌生、扩展的全过程．试验结果为表面硬化处理在碳化钨钢结硬质含金热作模具上的应用提供了理论依据．