Molten pool and temperature field in CO_2 laser welding

0IntroductionCompared with conventional welding methods,laserwelding has many advantages,such as large penetrationratio,small HAZ,small welding deformation.Another ad-vantage of laser welding is easy to weld complicated com-ponents because laser can be transferred by mirrors andoptical fiber.The laser welding will find wide applicationswith the laser system developing.Induced-plasma,molten pool and keyhole are mainphenomena in study of laser welding process.The varietiesof them indicate the …     

TiB2/Ti-Al复合材料中棒状TiB2晶体的微观特征

用XDTM法制备了TiB2/Ti-Al复合材料并利用XRD、SEM和TEM对复合材料的相组成和微观组织进行了研究.结果表明:复合材料中棒状TiB2的{1010}面存在与[0001]晶向垂直的薄片状凸耳,其厚度一般小于0.2μm,伸出表面高度可达4μm,并且这些凸耳的晶面取向与棒状TiB2本身是相同的;棒状TiB2一般以垂直交叉的十字或数个十字构成的辐射状形式分布于α2/γ层片基体中;在较快的凝固过程中,棒状TiB2固-液界面前沿产生的富Al、Ti边界层和随着棒状TiB2晶体的长大,导致固-液界面上B原子过饱和度不均匀性增加,共同作用使固-液界面失稳,从而形成了棒状TiB2的形貌特征.     

退火对Cu50Zr42Al8非晶合金电阻的影响

采用惠更斯电桥法和X射线衍射技术测试了Cu50Zr42Al8块状非晶合金在不同温度(500~600℃)保温20min和550℃保温不同时间(10~60min)条件下的电阻值与结构变化。研究发现,Cu50Zr42Al8块状非晶合金的电阻值在接近晶化温度Tx的515~520℃温度区间附近增加得较快,呈现出电阻极大现象,且随着退火温度的升高和保温时间的延长,电阻值均呈现出先增大后减小的变化趋势。     

几种液压同步新回路

介绍了几种带补偿措施的串联单杆液压缸新同步回路的结构、原理和特点。在新同步回路中，活塞上的密封圈不易损坏。     

金刚石薄膜涂层钻头加工高硬度钢的实验研究

为提高金刚石薄膜涂层的韧性，避免金刚石薄膜涂层脆性断裂，以自贡硬质合金厂生产ZK-10型号硬质合金钻头为基体，采用厚度大约为3μmTiC作为过渡层，在表面涂覆4μm～5μm厚度的金刚石薄膜制成金刚石薄膜涂层钻头。用于加工硬度为HRC61的经热处理的GCrl5钢板，分别与未涂层硬质合金钻头、TiC-TiN涂层钻头对比，结果表明，金刚石薄膜涂层钻头由于加工速率高，摩擦发热量少，有效地避免了铁元素在高温下将金刚石转化石墨的作用，结果使用寿命比未涂层硬质合金钻头提高10倍以上，同TiC-TiN涂层钻头相比，初期加工性能明显优越，加工速率成倍数提高．但使用过程中，性能衰减更快，导致总体使用寿命同TiC-TiN涂层钻头相差不大。在表面喷砂处理中，金刚石薄膜涂层大部分易于脱落，剩余部分呈岛状分布，说明金刚石薄膜与基体的结合力分布很不均匀，这可能与金刚石薄膜的形核过程密切相关。     

高强度冷矫直机机架结构优化分析

高强度冷矫直机机架由上横梁、立柱、底座用四根拉杆联结而成,对四根拉杆施以预紧力,使之成为预紧机架。由于底座和立柱都采用了薄壁结构,机架的局部变形对整体刚度影响较大,为了使机架具有较高的刚度,结合有限元分析技术对该矫直机机架进行了三维有限元分析及结构优化分析,取得了较好的效果。     

Microstructure and tensile properties of squeeze cast magnesium alloy AM50

High-pressure die cast magnesium alloy AM50 is currently used extensively in large and complex shaped thin-wall automotive components. For further expansion of the alloy usage in automobiles, novelmanufacturing processes need to be developed. In this study, squeeze casting of AM50 alloy with a relatively thick cross section was carried out using a hydraulic press with an applied pressure of 70 MPa. Microstructure and mechanical properties of the squeeze cast AM50 with a cross-section thickness of 10 mm were characterized in comparison with the die cast counterpart. The squeeze cast AM50 alloy exhibits virtually no porosity in the microstructure as evaluated by both optical microscopy and the density measurement technique. The results of tensile testing indicate the improved tensile properties, specifically ultimate tensile strength and elongation, for the squeeze cast samples over the conventional high-pressure die cast parts. The analysis of tensile behavior show that the strain-hardening rate during the plastic deformation of the squeeze cast specimens is constantly higher than that of the die cast specimens. The scanning electron microscopy fractography evidently reveals the ductile fracture features of the squeeze cast alloy AM50.     

Y2O3/TiO2复合空心微球的制备与表征

以表面富载羧基的聚(苯乙烯-丙烯酸酯)(PSA)阴离子乳胶粒为模板制备了PSA乳胶粒/钇盐水解产物/钛盐水解产物复合核壳微球,在空气中一定温度下煅烧后得到550 nm左右的内镶Y2O3的TiO2空心微球.用SEM、TEM、TG-DTG、IR和XRD对样品进行了分析表征.结果表明当钇盐水解产物包覆量/钛盐水解产物包覆量比值很小时,复合核壳微球煅烧后得到Y2O3/TiO2复合空心微球,当钇盐水解产物包覆量/钛盐水解产物包覆量比值较大时,煅烧复合核壳微球后得到新相Y2Ti2O7,导致球壳大部分破碎成小粒子.     

The integrated intelligent system for welding seam error and penetration depth identification

A integrated intelligent system for seam tracking and penetration control is given. The system received information of welding seam error and penetration depth from only one sensor, then, it realized seam tracking and penetration control simultaneously. This paper introduces constitution of the system, methods of information recognition, design of the neuralfuzzy controller and results practically.     

不同介质微束水蒸气等离子弧的切割性能

采用不同介质的水蒸气等离子弧进行了切割试验研究，试验研究表明，不同介质的水蒸气等离子弧具有不同的切割特点，乙醇或丙酮的加入，使水蒸气等离子弧切割性能得到明显的改善。