反应合成AgSnO₂材料组织均匀化过程的材料应力状态研究

【作者】 许福太；

【导师】 陈敬超；

【作者基本信息】 昆明理工大学 ， 材料学， 2009， 硕士

【摘要】 AgCdO材料曾一度被认为是最好的电接触材料,它具有优良的灭弧性能,在中等负荷开关中具有“万能触点”之称。然而,随着电器开关不断对电触点提出的小型化、高可靠性、长寿命等苛刻的性能要求,AgCdO材料不仅在抗磨损、抗熔焊、耐电弧浸蚀等性能指标上已显露明显不足,而且AgCdO触点燃弧产生的Cd蒸气有毒,不符合环保要求。AgSnO2由于其优良抗电弧侵蚀性、耐磨损性、开关运行特性和更好的抗熔焊性而成为最有希望代替AgCdO的一种材料。但是,相对AgCdO而言,采用常规方法制备的AgSnO2的加工性能要差得多,在线材拉丝时很容易出现断线的情况。使得规模生产无法得到有效保证,而且在铆钉的打制过程中也较容易出现开裂现象。本课题利用有限元方法,模拟AgSnO2的挤压过程,分析了挤压过程中第二相颗粒的分布情况、应力应变行为、速度位移情况以及挤压力变化情况；并与实验结果相比较,分析变形规律,为AgSnO2材料的产业化生产提供有效的理论依据。本文利用MSC.Marc有限元软件,模拟了纯银的挤压过程,AgSnO2的传统一次挤压和多梯度变径一次挤压过程,以及真应变为4、7.25、10、12.5的挤压过程。从纯银的挤压模拟过程中可以看出,金属的流动情况与实际非常相似,并分析了银的应力、应变情况。AgSnO2的传统一次挤压和多梯度变径一次挤压的模拟结果表明：在挤压过程中,应力主要集中在Sn02颗粒上,且变化较大,而Ag基体所受到的应力较小且较为平稳；Ag基体的塑性应变要比Sn02颗粒的塑性应变大,在挤压过程中,Sn02颗粒几乎不变形；随着挤压比的增大,挤压力增大；相对于传统一次挤压,多梯度变径一次挤压过程中材料的边部的速度与中心材料的速度的差值没有传统一次挤压的差值大,这将有利于减少材料的缩尾的现象的产生；相对于同一挤压变形量而言,多梯度变径一次挤压的挤压力要比传统一次挤压的挤压力小。比较真应变为4、7.25、10、12.5AgSnO2的挤压模拟结果可出：随着挤压真应变的增大,Sn02颗粒的分布情况如下：Sn02颗粒围成环状,渐渐被挤压成扁椭圆、带状,经过多次的挤压后,最后均匀地分布在Ag基体中,达到理想的效果。更多还原

【Abstract】 AgCdO material was once considered to be the best electrical contact material. it has fine performance of extinguishing arc, which was called the "universal contact" in the field of middle-load switches. However, with the harsh performance requirements such as going miniaturization, high-reliability, long life on the electrical contact, AgCdO material has shown the obvious insufficiency in anti-attrition, anti-melt weld, arc erosion-resistant and so on. Moreover, as its toxin, does not meet the environmental protection requirement. Because of its fine anti-arc erosion, wearability, switching and better anti-melt welds, AgSnO2 becomes the most promising substitute for AgCdO material.However, the machinability of AgSnO2 which was made by the conventional method is much worse than AgCdO. It is very prone to break in the wiredrawing situation. It will be unable to ensure the scale production. Moreover, It will be also more prone to crack in riveting process.The finite element method was used in this object. The extrusion process of AgSnO2 material was simulated. The distribution of particles, the relation of stress and strain, the velocity and displacement, and the force were analyzed. The last, comparing with experimental results, analyzing the law of deformation, it will offer an effective theoretical foundation for the industrialization manufacture of AgSnO2 material.In this paper, MSC.Marc finite element software was used to simulate the extrusion of pure silver. Traditional one extrusion and multi-gradient adjustable radius one extrusion of AgSnO2 were simulated. As well as extrusion processesing were simulated which the true strain is 4,7.25,10 and 12.5.It can be seen from the silver extrusion simulation processing that the flowing of metal was very similar to the actual situation. The stress and the strain of silver were analyzed.Result of the traditional one extrusion and multi-gradient adjustable radius one extrusion of AgSnO2 extrusion simulation show that:In the course of extrusion,the stress is concentrated on the SnO2 particles mainly, and changes, quickly. And the stress of the Ag matrix is smaller and more stable; The equivalent of plastic strain of the Ag matrixs is greater than SnO2 particles. In the course of extrusion, the SnO2 particles do not deform nearly; With the extrusion ratio greater, the force of extrusion is greater too. Comparing with traditional one extrusion, the margin of the velocity between the surface part of the ingot and the center of the ingot is less in multi-gradient adjustable radius traditional one extrusion. It will help to reduce the phenomenon of shrinking in the end of material. Compared to the same deformation, the force of multi-gradient adjustable radius one extrusion is less than one extrusion.Comparing with the result of AgSnO2 extrusion simulation which the true strain is 4, 7.25,10,12.5, with the true strain increasing, we can find out that those SnO2 particles which reprent as the ring-type,are extruded gradually into the oblate or fibriform shape, through a series of extrusion, uniformly distributed in a Ag matrix, achieving the ideal effect finally.更多还原