Development of controlled fracture forming process for advanced functional materials

由于传统的塑性加工方法不适用于陶瓷、金属间化合物及其复合材料的脆性加工，因此，近净成形是处理这些材料的必要选择。通常的粉末成形技术有时不足以生产出性能均匀或形状均匀的高质量功能性产品。通过三年的研究，我们开发了陶瓷复合线材和板材的可控断裂成形工艺（简称CFFP）。在基础研究的基础上，我们发现：(1)直径均为300mum的Ni/SUS316-alphaAl_2O_3丝材可制得长度为10 m的丝材；(2)从初始密度较低的α - al_2o_3预烧结坯料开始，CFFP大部分由剪切断裂过程控制，断裂颗粒在压缩压力约束下重排和流动；(3)接丝和板形的平均临界减量接近90-95%。(4) cffp诱导的显微组织控制可获得良好的烧结性能，降低烧结温度100-200℃，抑制晶粒长大，最终密度可达到99%以上。因此，该生产技术应被推荐为未来的候选成形方法，以实现无粘结剂和玻璃精细陶瓷的近净成形和微观结构控制。

New alternative near-net shaping is indispensable to deal with ceramic, intermetallics and their composite materials since the conventional plastic working cannot be applied to these types of brittle materials. Usual powder forming technologies are sometimes insufficient to yield good-quality functional products with homogeneous properties or uniform shapes. Through our three year research project have been developed the controlled fracture forming process (abbreviated by CFFP) for ceramic composite wires and plates.On the basis of the fundamental studies, we have found that(1) Ni/SUS316-alphaAl_2O_3 wires with uniform diameter of 300mum can be produced up to 10 meters,(2) starting from the lower initial density alpha-Al_2O_3 pre-sintered billet, most of CFFP is governed by the shear fracture process with the fractured particle rearrangement and flow under the compressive pressure constraint,(3) the average critical reduction both in wiring and plate forming approaches 90-95%, where the green density of mass becomes 90-92% T. D. and the average particle size 0.3mum for the initial particle diamete 0.9mum,(4) good sinterability is attained by CFFP-induced microstructural control : the sintering temprature can be lowered by 100-200ﾟC, the grain growith is surppressed, and final density reaches 99% T. D. and more.Hence, this productive technology should be recommended as the candidate future forming method to realize nearnet shaping together with microstructural control for fine ceramics without binders and glasses.