Development of Non-Equilibrium PM Process to Precision Forming of Hard Materials using Pseud-Superplasticity

对Ti/Si系合金和W合金进行了系统的研究，重点研究了非平衡相变到平衡相变等伪超塑性变形行为。结果，观察到了与常规超塑性非常相似的大变形。此外，还证实了该合金在高应变率下发生了低温低应力变形。变形行为可以通过控制显微组织和初始相组成来控制。基于这些基本发现，使用立命馆大学的同步辐射研究设施，并利用同步辐射设施的LIGA工艺对微尺寸零件进行了精密成形。对于初始状态为非平衡状态的Ti-20质量%的碳化硅粉末，非晶相的晶化导致了大量的低温变形。这种现象可能是由于由非晶相加热形成的材料中存在纳米尺寸的颗粒所致。此外，从低温超塑性角度对机械球磨W(W)粉末进行了研究。结果表明，纳米晶控制的W粉末压坯具有良好的压缩变形性能，证明了纳米晶组织控制是一种有效的低温低应力成形工艺。

Systematical researches have been carried out using Ti/Si system alloy and W alloy, focusing especially to a pseudo-superplastic deformation behavior such as non-equilibrium to equilibrium phase transition. As a result, a large deformation very similar to conventional superplasticity was observed. In addition, it was confirmed that a low temperature and a low stress deformation under a high strain rate took place by the phase transition. The deformation behavior was able to be controlled by controlling the microstructure as well as by an initial phase constitution. The synchrotron radiation research facility of Ritsumeikan University was used based on these basic findings, and a precision forming of micro-size parts was applied with the LIGA process of the synchrotron facility. In case of a Ti-20mass%SiC powder with a non-equilibrium at the initial state, crystallization of an amorphous phase enabled a large amount of low temperature deformation. This phenomenon is presumably due to the existence of the nano size grains in the material formed from the amorphous phase by heating. Moreover, mechanically milled W (tungsten) powders were investigated from the point of view of low temperature superplasticity. As a result, nano grain controlled W powder compacts showed outstanding deformation properties by compression test, thus the nano grain microstructure controlling is proved to be an effective process for the low temperature and the low stress forming.