【作者】 张龙；

【导师】 李剑中；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2012， 硕士

【摘要】 陶瓷材料因其优良的物理化学性能,在微机电系统、微零件和微结构中具有广泛的应用需求。结合微细刀具在线制作和陶瓷预烧结体加工,可以较快地加工出陶瓷微细结构。其中,预烧结可提高坯体强度,有利于减小微细加工对象的边缘破损,但强度过高将加剧刀具磨损。目前对陶瓷预烧结体强度随预烧结条件的变化规律尚未完全明了,急需针对微细加工特点设计合理的预烧结体强度。对于陶瓷粉末压坯的烧结,烧结温度和烧结时间对颗粒间烧结颈的生长有着重要影响,而烧结颈的大小又决定着陶瓷坯体的强度变化。本文对氧化铝生坯进行了不同温度和不同时间下的预烧结,并参照三点弯曲法对得到的预烧结体(坯体)进行强度测试；同时对颗粒间的烧结颈进行了理论估算,借鉴粉末冶金中的强度模型预测了陶瓷预烧结体的强度。从抗弯强度测试结果可以看出,坯体强度随着预烧结温度的增加几乎呈指数关系而快速增加,但随着预烧结时间的增加却增加缓慢；根据强度理论预测的结果,实测值和预测值的变化趋势完全一致,且相符程度较好。从而在理论上建立了坯体强度与预烧结温度和时间的关系,为微细加工中坯体强度的设计和预烧结条件的合理选择奠定了理论基础。陶瓷微细加工中,坯体强度的大小直接影响边缘质量和刀具磨损,刀具磨损则直接影响微结构的尺寸精度,所以坯体强度的合理设计对于微细加工非常重要。本文结合不同加工参数下的试验探索,对不同强度的预烧结坯体进行了微细长槽加工,通过定量表征微细结构的边缘破损尺寸以及刀具轴向磨损量和其端部形状变化程度等,确定了坯体预烧结强度对边缘破损程度和刀具磨损的影响规律,为在微细加工中优化选择坯体的预烧结强度提供了依据。通过实际加工实验证实,在本文实验条件下,如果综合考虑边缘质量和刀具磨损,坯体强度以7.302-9.404MPa为好,且走刀速度不宜过小,主轴转速越小越好。其中,选择上限有利于提高微细结构的边缘质量,且走刀速度越小越好；选择下限,则可提高预烧结体的制备效率,同时减小加工过程中的刀具磨损。所有研究结果表明,综合考虑加工条件、以及坯体预烧结强度对边缘破损和刀具磨损程度的影响,对强度进行优化选择,进而通过坯体强度理论预测模型合理设计预烧结工艺,进而获得理想的坯体强度,是提高陶瓷微细加工质量和效率的有效方法。更多还原

【Abstract】 Ceramics is widely used in micro components and micro features because of its excellent properties such as resistance to erosion and high temperature. Ceramic micro structure can be easily processed by machining pre-sintered compact. In the machining process, the strength of pre-sintered compact has a significant impact on edge quality and tool wear. However, the relationship between compact strength and pre-sintering condition is not clear. It is also necessary to select the optimal strength of pre-sintered alumina for micro machining.Pre-sintering temperature and time are key factors that affect the strength of ceramic compact by controlling the growth of sintering neck between particles. In this paper, alumina green compacts were pre-sintered, and then three-point flexure strength tests were carried out. Meanwhile, the theoretical strength of pre-sintered compact was obtained by calculating the size of sintering neck. From experimental results, it can be seen that strength is an exponential function of pre-sintering temperature and is also a logarithmic function of pre-sintering time approximately. And theoretical strengths match well with the experimental values. Therefore the model and be used to select the proper strength and its pre-sintering condition.In micro-machining, the edge quality of machined micro features and tool wear are directly influenced by the strength of alumina. In this paper, experiments of under different machining parameters and strength were carried out. The evaluation parameters such as damage extent of edge length, width of edge damage, length of tool wear and shape change of tool end was also been established. And the relationship between evaluation parameters and strength provides a basis for optimal selection of strength. The experimental results show that7.302-9.404MPa is the proper choice when both edge quality and tool wear are taken as the evaluation parameters. The higher strength will improve edge quality. And the lower strength will improve the efficiency of preparing pre-sintered alumina and reduce the tool wear.In summary, it is an effective way to improve the machining equality and efficiency that optimizing pre-sintering conditions and strength selection, which are respectively based on the theoretical prediction model and the relationship between strength and evaluation parameters.更多还原