Alternative Title摩擦攪拌プロセスによるZn-22Al超塑性合金の革新的機能の創成
Note (General)J-GLOBAL ID : 201801016373837352
This dissertation is a systematic study on the developments of innovative functions for Zn-22Al superplastic alloy through friction stir processing (FSP), which is a type of friction stir welding (FSW).Superplastic materials are fine-grained polycrystalline solids that have recently gathered interest because of their excellent tensile elongation and behavior in superplastic forming (SPF) technology. SPF is a forming method that produces complex shaped parts in a single forming process. The grain size, which is one of the most important superplastic parameters, affects the strain rate and ductility in grain boundary sliding (GBS). In GBS, a smaller grain size leads to a larger grain boundary area that results in higher elongation and therefore more favorable superplastic behavior.In the present study, we concentrated on Zn-22Al, a commercial superplastic alloy having a wide range of applications in different fields of studies. Zn-22Al has a seismic property, which makes it applicable in buildings for energy absorption during earthquakes. Zn-22Al is also used for electronic enclosures, cabinets and panels, business machine parts, and medical and other laboratory tools. Zn-22Al has the characteristic of reaching its highest superplasticity at a relevantly lower temperature comparing other conventional superplastic alloys and can be used for superplastic forming and diffusion bonding purposes. However, applications of Zn-22Al receive some limitation especially in structural industries such as easily deformation under constant pressure due to its high strain rate sensitivity. Therefore, methods of improving mechanical properties of Zn-22Al, also developing new techniques for manufacturing new composites of this alloy would become essential.The FSP technique, which is a relatively new processing method requiring fewer processing parameters, was used in the present study to refine the grain structure and improve the mechanical and superplastic properties of Zn-22Al. The results revealed FSP can achieve fine grains and improve the superplastic properties of Zn-22Al.In addition, FSP was used for a novel forming method, known as friction stir forming (FSF), to produce multi-functional superplastic composites. By using the FSF technique, perforated steel sheet was mechanically interlocked between Zn-22Al sheets to produce a superplastic damping sheet with outstanding damping capacity. Moreover, insulated copper wire was mechanically interlocked within Zn-22Al alloy to produce a multi-functional superplastic alloy with the ability to transfer information or energy.Finally, FSF can improve the mechanical properties of Zn-22Al superplastic alloy by interlocking the stainless steel strands within the alloy. Using the friction stir based technique can have a significant scientific impact on the production of functional composites with respect to both mechanical engineering and electrical engineering.
平成29年度
application/pdf
Collection (particular)国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
Date Accepted (W3CDTF)2018-08-03T23:36:01+09:00
Data Provider (Database)国立国会図書館 : 国立国会図書館デジタルコレクション