GRAIN REFINEMENT IN BULK UNDERCOOLED Ni-BASED ALLOY

Fluxing of 5 g bulk melt Ni77Si13B10 permits high undercoolings to be attained prior to nu-cleation onset.Investigations of grain refinement in the bulk undercooled alloy as a function ofundercooling,recalescence behavior and cooling rate have been reported.A significant inhomo-geneity of reduction in grain size of a bulk sample is observed,which is caused by the different so-lidification conditions:(1)recalescence process,and(2)the followed plateau in which the heatrelease and extraction rates are equal.It is concluded that the homogeneous refined microstructurecan be achieved if the initial undercooling prior to nucleation,or cooling rate after recalescence isfurther increased.     

激光退火对Inconel 718微观组织和硬度的影响

研究激光退火对Inconel718时效合金的显微组织和硬度的影响.一台2.5kW的CO2激光机被用来照射试样的表面.在激光能作用下,试样表面层被加热后空冷.通过控制激光工艺参数,在表面不发生熔化的前提下,能够使一定厚度表面层内的硬度降低到标准退火合金的水平,而不影响试样内部母材的硬度.显微组织观察显示表面层的基体强化相(γ″和γ‘)在激光照射过程中被固溶,而其它二次相没有变化.γ″和γ‘的固溶被确定是表面层硬度下降的原因.在其它试验条件不变时,确立了退火层生成时由激光散焦距离和扫描速度描述的工艺参数范围.     

钎焊-热轧复合工艺制备不锈钢/碳钢复合板

针对不锈钢/碳钢复合板爆炸-轧制复合工艺存在的主要问题,提出了钎焊-热轧制备新技术,研究了主要工艺参数对钎焊复合板结合强度的影响,分析了钎焊复合板热轧的结合机理,测试了复合板的主要力学性能.结果表明,采用自制的银基钎料可以实现不锈钢/碳钢有效的钎焊结合,理想的钎焊工艺参数为:钎焊温度755～770 ℃,钎焊时间2.5～3 min.热轧过程中钎料层表现出了良好的塑性,压下率为40%时,轧后钎料层未出现断裂、分层.轧制中钎料层同基体形成的金属键显著提高了不锈钢/钎料界面的结合强度,热轧复合板的抗剪强度达到了342.6 MPa.     

激光熔覆镍基粉末涂层的研究

分析了激光熔覆表面处理技术对镍基自熔性合金粉末材料性能的要求，研究了合金粉末的化学成分、微观组织及熔覆层的性能，并对涂层的耐磨性进行了分析。     

基于计算机视觉的焊点缺陷检测系统的设计

在点焊机的焊接生产线上,由于焊接工艺的不成熟,往往会导致虚焊、漏焊、焊穿等现象,会极大地影响产品的使用寿命、美观等,需要对其进行质量检测.针对传统检测方法的低效率,提出采用机器视觉的方法来对焊点进行检测,并给出一种图像处理方法:对图像进行平滑处理,然后使用Otsu方法对图像进行阈值分割,并对得到的图像做倒三角距离变换,将像素点信息转化为灰度信息,采用分水岭算法准确地分割出焊点,最后通过面积等特征计算对焊点缺陷进行分类.实验证明,该方法较传统的检测方法,能有效地检测出多种不同排列的焊点,提高了工业生产效率.     

基于小波包变换与Wiener滤波的SMT焊点图像去噪技术

针对目前SMT(surface mount technology)焊点图像去噪效果不理想的问题,提出了一种基于小波包变换与wiener滤波的SMT焊点图像去噪新方法.利用小波包对图像进行分解,可以同时对SMT焊点图像的低频和高频部分进行多层分解,有利于保留图像信息,减少噪声对图像的影响.通过对图像的小波包系数的分析,对小波包树高频系数进行Wiener滤波,保留低频系数;然后进行小波包反变换,重构得到SMT焊点去噪后图像.实验表明,提出的方法不仅可以有效地去除SMT焊点图像的噪声,而且能很好地保留原图像的边缘信息,与传统方法相比,去噪性能和去噪声效果有一定的提高.     

SOD-323型双端器件焊点防开裂技术研究

针对某电源模块产品中的SOD-323型双端器件在环境试验中出现焊点开裂的失效问题,对其焊点开裂机理进行研究。结合三防漆的温度特性,对其进行仿真和多种条件下的应力试验摸底。根据试验结果,提出了针对SOD-323型双端器件焊点开裂的应用解决方案。     

Ni元素对Sn-9Zn-3Bi无铅钎料显微组织和性能的影响

利用真空箱式电阻炉制备了Sn-9Zn-3Bi-xNi无铅钎料合金,并对其显微组织和主要性能(熔点、熔程、抗氧化性、润湿性、剪切强度)及钎焊接头断口形貌进行了分析。结果表明,少量Ni的加入可以细化Sn-9Zn-3Bi合金的显微组织,而对其熔点影响较小。当Ni添加量为0.1%和0.5%时,钎料的熔程变化不大,Ni添加量为1%时,钎料的熔程增大比较明显。随着Ni添加量增多,无铅钎料的抗氧化性能和润湿性能提高。Ni添加量在0.1%和0.5%时,钎焊接头的剪切强度变化不大,但韧性增加;Ni添加量在1%时,钎焊接头的剪切强度略有增大,但韧性降低。     

Stress dependence of the creep behaviors and mechanisms of a third-generation Ni-based single crystal superalloy

Elevated temperature creep behaviors at 1100℃ over a wide stress regime of 120–174 MPa of a thirdgeneration Ni-based single crystal superalloy were studied. With a reduced stress from 174 to 120 MPa,the creep life increased by a factor of 10.5, from 87 h to 907 h, presenting a strong stress dependence.A splitting phenomenon of the close-(about 100 nm) and sparse-(above 120 nm) spaced dislocation networks became more obvious with increasing stress. Simultaneously, a_0010 superdislocations with low mobilities were frequently observed under a lower stress to pass through γ'precipitates by a combined slip and climb of two a_0110 superpartials or pure climb. However, a_0110 superdislocations with higher mobility were widely found under a higher stress, which directly sheared into γ'precipitates.Based on the calculated critical resolved shear stresses for various creep mechanisms, the favorable creep mechanism was systematically analyzed. Furthermore, combined with the microstructural evolutions during different creep stages, the dominant creep mechanism changed from the dislocation climbing to Orowan looping and precipitates shearing under a stress regime of 137–174 MPa, while the dislocation climbing mechanism was operative throughout the whole creep stage under a stress of 120 MPa, resulting a superior creep performance.     

微电子封装中焊锡接点的界面应力奇异性

采用界面力学理论计算了不同形状的含铅/无铅焊锡接点界面应力奇异性指数,建立了焊锡接点的有限元模型,计算了线弹性、弹塑性和Johnson-cook材料模型的界面应力分布.结果表明:随着焊锡接点接触角的增加,界面应力奇异性增强;Sn37Pb/Cu界面比Sn3.5Ag/Cu和Sn3.0Ag0.5Cu/Cu界面的应力奇异性明显;弹塑性变形和应变率效应降低界面应力.