薄板激光拼焊工艺研究

汽车薄板的激光拼焊可以减轻整车质量和制造成本,对提高汽车设计的灵活性具有重要意义.通过对汽车用冷扎薄钢板和镀锌板的激光拼焊的实验研究,表明虽然激光焊接接头的塑性有所下降,但其焊接强度与母材差不多,且焊接影响区小,对汽车覆盖件和地板等零件的焊接获得很好的效果.     

High-rate capability of spinel LiNi0.05Mn1.95O4 cathode for Li-ion batteries prepared via coprecipitated precursor

Spinel LiNi0.05Mn1.95O4 cathode material for lithium ion batteries was synthesized by solid-state reaction from coprecipitated Ni-Mn hydroxide precursors and characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and galvanostatic charge-discharge tests. It is found that LiNi0.05Mn1.95O4 powder has an ordered cubic spinel phase （space group Fd3m） and exhibits superior rate capability. After 450 cycles, the LiNi0.05Mn1.95O4/carbonaceous mesophase spheres（CMS） Li-ion batteries can retain 96.0% and 93.3% capacity at 5C and 10C charge/discharge rate, respectively, compared with 85.3% （5C） and 80.5% （10C） retention for LiMn204 batteries. However, the initial discharge capacity of LiNi0.05Mn1.95O4/CMS batteries at 1C charge/discharge rate （96.20 mA.h/g） is slightly lower than that of the LiMn2O4 batteries （100.98 mA.h/g） due to the increased average oxidation state of Mn inLiNi0.05Mn1.95O4.     

Creep behavior and microstructure evolution of directionally solidified superalloy IC 10 at high temperature

The creep behavior of directionally solidified （DS） superalloy IC 10 was investigated under 192 MPa and 218 MPa at 980 ℃. Under the testing conditions, the marked creep characteristic of the superalloy is that the creep curve has a short primary and secondary stage and a long tertiary stage. Another creep characteristic is that the superalloy has excellent plasticity at high temperature. To study the creep behavior, the microstructure was observed by SEM and TEM. Different from other microstructure of Ni-base superalloys, superalloy IC10 forms incompletely rafted γ＇ phase during the creep processes. To understand the creep deformation mechanism of superalloy IC10, the movement of dislocations was analyzed. The results show that the dislocations moving in the γ matrix and climbing over the γ＇ precipitates is the main deformation mechanism under the experimental conditions.     

The Study of Plasma Nitriding of AISI304 Stainless Steel

This paper presents results on the plasma nitriding of AISI 304 stainless steel at different temperatures in NH3gas. The working pressure was 100～200 Pa and the discharge voltage was 700～800V. The phase of nltrided layer formed on the surface was confirmed by X-ray diffraction. The hardness of the samples was measured by using a Vickers microhardness tester with the load of 50g. After nitriding at about 400℃ for two hours a nitrided layer consisting of single γN phase with thickness of 51.tm was obtained. Microhardness measurements showed significant increase in the hardness from 240 HV (for untreated samples) up to 950 HV (for nltrided samples at temperature of 420℃). The phase composition, the thickness, the microstructure and the surface topography of the nltrided layer as well as its properties depend essentially on the process parameters.     

Microstructure and tensile properties of magnesium alloy modified by Si/Ca based refiner

Microstructure and mechanical properties of pure magnesium and AZ31 alloy with Ca/Si based refiner addition were investigated. The results indicate that addition of Ca/Si based refiners to pure magnesium and AZ31 alloy results in remarkable microstructure refinement. With proper amount of refiner addition, the grain size in as cast ingots can be one order of magnitude lower than that without refiner addition. Small amount of refiner addition to AZ31 alloy increases both ultimate strength and yield strength significantly,while the ductility of the alloy with refiner addition is similar to that without refiner addition. Addition of refiner improves the deformability of AZ31 alloy and extruded or hot rolled specimens （rods or sheets） with refiner addition exhibit higher surface quality and mechanical properties than those without refiner addition.     

低碳钢箔片氧化原因探讨

介绍了用低钢箔片（挂片）在对Unicase密封箱式炉进行炉内碳势定碳分析时存在被氧化的情况。经过分析后认为低碳钢箔片的氧化（除操作失误外）是由于以下两种原因造成：（1）箔片在冷却腔冷却过程中其腔内的温度下降导致压力下降，从而空气进入冷却腔，而此时箔片的温度尚未冷却到200℃以下，箔片发生氧化。（2）由于冷却水的作用，使冷却腔的温度降至露点以下，冷却腔内气氛（与炉内气氛相同）中的水蒸气被凝结，液态的水对炽热的箔片造成了氧化，在此基础上，提出了改进措施。     

铸件热应力及热裂的数值模拟研究

铸件在铸造凝固过程中热应力场及热裂的数值模拟在实际的生产实践中起着十分重要的作用。本文综合国内外对铸造凝固过程中热应力及热裂数值模拟研究的现状，结合中北大学铸造工程研究中心的实际情况，指出了今后的研究方向和重点：建立适合铸造过程应力场数值模拟的模型，采用有限元软件ANSYS实现铸件热应力场的模拟分析，并计算残余应力。     

Fe-66.7%Si合金液滴落管实验的动力学和传热学计算

从动力学和传热学角度对Fe-66.7%Si（原子分数）合金液滴在充入不同种类和压力保护气体的落管中下落的运动过程和温度变化情况进行了计算分析.从重力水平和熔体冷却速率等方面对该合金液滴落管凝固实验的保护气体种类和压力选择进行了讨论.     

注塑产品动态装配模型的集成知识模型研究

基于MBR(基于模型的推理)技术，建立了注塑模具动态装配结构模型；基于RBR(基于规则的推理)技术，应用面向对象的规则模型(OOR)，建立了动态装配规则的知识表示模型。最后，该文将两种知识表示模型集成，建立了完整的知识模型，为整个系统的后续工作奠定了基础。