Method of Forming Composite Structure from Different Kinds of Ceramics by Using Injection/Compression Molding

烧结性能取决于陶瓷材料和添加剂。不同种类的陶瓷或不同添加量的陶瓷的适当组合可能会在烧结件上产生残余应力，使零件变得坚韧。本研究考察了不同烧结条件下的烧结速度和烧结过程中的应变速率。此外，还考察了脱蜡过程中毛坯成型件的变形特性，因为在注射成型过程中，特别是在高剪切速率区域发生了相当大的变形。研究结果总结如下：(1)发现成型件中产生了对应于聚合物分子伸长或收缩的残余应变。在脱蜡过程中加热时，会引起很大的变形。(2)烧结率，或密度率，取决于。关于烧结助剂的数量，比如氧化铝材料中的氧化镁。在1,400℃时，烧结助剂的不同所对应的烧结率差异较大。C-L，500岁。C.烧结率在1600℃饱和。C.(3)通过对简支梁自重挠度的测量，研究了烧结阶段应变速率与应力的关系，并用一个简单的表达式表达出来。(4)采用两步注射成型工艺制作了三柱试件，每根试件中含有不同量的添加剂。在脱蜡和烧结后，用应变片检测每根柱子的残余应力。最后发现，在加入大量烧结助剂的立柱中观察到了拉应力，而在其他加入少量助剂的立柱中则观察到了压应力，这表明在零件表面施加适当分布的烧结助剂可以使零件表面产生压应力。

Sintering property depends on ceramics material and additives. Appropriate combination of different kinds of ceramics or those with different amount of additives may cause residual stress in a sintered part and it makes the part tough. In this research, sintering rate and strain rate in sintering process are examined in various sintering conditions. Furthermore, distorsion property of a green molded part in dewaxing process is also examined, because considerable amount of distorsion is found to occur, especially in the region of high shear rate in injection molding process.Results are summarized as follows :(1) It was found that residual strain, corresponding to the elongation or shrinkage of polymer molecules, is generated in a molded part. It causes large deformation, when the part is heated in dewaxing process.(2) Sintering rate, or density rate, depends. on the amount of sintering additives, say MgO in the case of alumina material. Difference of sintering rates corresponding to the difference of sintering additives becomes large at the temperature of 1,400。C-l, 500。C.Sintering rate saturates at 1,600。C.(3) Relationship between strain-rate and stress in sintering stage is examined from measurement of self weight defection of a simply supported beam, and it was expressed by a simple expression.(4) A three pillar specimen, in which each pillar contains different amount of additives, is made by two stage injection molding. After dewaxing and sintering, residual stress in each pillar is examined by strain gages. Finally, it was found that tensile residual stress is observed in a pillar with large amount of sintering additives and in other pillars with small amount of additives compression stress is observed, It suggests that it is possible to make compression residual stress in surface of a part by applying appropriate distribution of sintering additives.