Abstract
We developed a fabrication technique for microdies made of titanium superplastic alloy. This technique consists of the following three processes: (1) microshapes are formed on Si substrates by a micromachining technique, (2) a functionally gradient layer of TiN/Ti is deposited on the Si base structures by sputtering, and (3) the Si base structures are imprinted with a Ti alloy using a vacuum hot press machine. In the third process, the functionally gradient layer is diffusion bonded to the Ti alloy simultaneously. In this technique, superplastic working of Ti alloy (SP700) is carried out to realize high precision forging at the microlevel. In addition, the functionally gradient layer of TiN/Ti is bonded over the Ti alloy to attain a surface roughness at the nanolevel. In this study, to satisfy these requirements of the Micro Electro-Mechanical Systems device, the working conditions such as working temperature, strain rate, final reduction in height of the Ti alloy specimen and thickness of the sputtered layer of TiN/Ti were optimised.
