Study on modification of joining layer structures of ceramic/metal bondings with heat treatment

为了获得耐热和高断裂强度的陶瓷/金属连接，通过对焊料和中间层材料的筛选试验，最终选择了Ti(1.5um)-Cu(20um)-Ni(镍中间层的一部分)和Ni(T)-W(t=1 mm)-Ni(t=1 mm)三层结构作为候选焊料和中间层材料。结果表明，当镍中间层厚度为1.3 mm左右时，室温下的断裂强度最大，为240 Mpa。断裂强度随试验温度的升高而增加，在400ﾟC时达到290 Mpa左右，然后逐渐下降，但在800ﾟC时仍高于180 Mpa。在真空中加热1000ﾟC至100小时后，断裂强度和拉伸粘结层结构变化不大。在氧化气氛中，如在空气中，发现这种结合的高断裂强度为k…。当温度达到600ﾟC及以上时，由于钨层的选择性氧化，断裂强度迅速下降。为了替代钨，必须开发一种具有抗氧化性能的中间层，目前正在研究中。利用超声显微镜对陶瓷与金属结合时表面产生的热残余应力进行了无损评估。该方法的原理是测量泄漏声表面波的速度，其速度随应力条件的变化而变化，即速度随拉应力的减小而减小，反之则随应力的变化而减小。这一新技术使我们能够测量陶瓷/金属连接界面附近的应力分布。得到的结果是合理的，除了几个新的发现是无法用现有知识解释的。为了理解这些新的结果，需要进一步的理论和实验研究，我们的实验室正在进行这些研究。较少

To produce ceramic/metal bondings with heat resistance and high fracture strength, five items were experimentally investigated and could be summarized as follows: From screening tests of solder and interlayer materials for depression of thermal residual stress, triplex layer structures of Ti(1.5um)- Cu(20um)-Ni(a part of nickel interlayer) and of Ni(t)-W(t=1mm)-Ni(t=1mm) were finally selected as candidate solder and interlayer materials. It was found that a maximum fracture strength of 240MPa was obtained at room temperature when a thickness of nickel interlayer is about 1.3mm. This fracture strength increased with increase in test temperatures and reached about 290MPa at 400ﾟC and then decreased gradually, but it is still higher than 180MPa at 800ﾟC. The bonding was heated at 1000ﾟC up to 100hr in vacuum and showed little change in fracture strength and raction bonding layer structures. In oxidizing atmospheres as in air it was found that a high fracture strength of this bonding was k … More ept up to 600ﾟC and above this critical temperature a fracture strength decreased rapidly due to the selective oxidation of the tungsten layer. Instead of tungsten an interlayer with anti-oxidation property has to be developed and is now under progress.A ultra-sound microscope was used for non-destructive evaluation of thermal residual stress developed on the ceramic surface when it was joined to metals. The principle of this method is to measure velocity of leaky surface acoustic wave, which changes dependent on stress conditions, namely, the velocity decreases with tension stress and the reverse case is for compressive stress. This novel technique enables us to measure stress distribution in the vicinity of ceramic/metal bonding interface. The results obtained are reasonable, except several new findings which is unexplainable using existing knowledges. In order to understand these new results further theoretical and experimental investigations should be required and are under progress in our laboratory. Less