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

烧结性能取决于陶瓷原料和添加剂。不同种类的陶瓷或添加剂含量不同的陶瓷的适当组合可以在烧结件中产生残余应力，使零件坚韧。在本研究中，在不同的烧结条件下，烧结速率和烧结过程中的应变速率进行了研究。此外，还研究了绿色模制品在脱蜡过程中的变形特性，发现在注射成型过程中，特别是在高剪切速率区，会产生相当大的变形，结果如下：（1）发现在模制品中会产生与聚合物分子的伸长或收缩相对应的残余应变。在脱蜡过程中，零件受热会产生较大的变形。(2)烧结率，或密度率，取决于。烧结添加剂的量，例如在氧化铝材料的情况下的MgO。在1400 ℃的温度下，与烧结添加剂的不同对应的烧结速率的差异变大。C-1，500。C.烧结速率在1600时饱和。C. (3)通过对简支梁自重变形的测量，研究了烧结阶段应变率与应力的关系，并给出了一个简单的表达式。(4)通过两阶段注射成型制备三柱试样，其中每个柱包含不同量的添加剂。在脱蜡和烧结之后，通过应变计检查每个柱中的残余应力。最后发现，添加剂含量高的一个柱体中存在残余拉应力，而添加剂含量低的另一个柱体中存在残余压应力。这表明，通过适当的添加剂分布，可以使零件表面产生残余压应力。

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.