Hisaki Watari is a Professor in Divion of Mechanical Engineering at Faculty of Science and Technology of Tokyo Denki University (Hatoyama Campus) since April 2015. From 2017 to the present, he served as Division Chair of the Division of Mechanical Engineering of the Faculty of Science and Technology at Tokyo Denki University. He received a B.Engng. from Kyushu University in Naval Architecture, 1985 in the School of Engineering at Kyushu University. He received his Ph.D. in Mechanical System engineering from Gunma University in Japan, 2006. Since April in 1988, he worked at Oyama National College of Technology as a Research Associate, Lecturer and Associate Professor until November 2006. Between 1999 and 2000, he visited at UMIST as a visiting researcher of Japanese Government. From November 2006 to March 2015, he worked as a Associate Professor and a Professor at Gunma University. From April 2015 to the present, he has been working at Tokyo Denki University as a full-time Professor. He has served as a chair of the Japan Association of Aluminum Forging Technology since 2014.
His research interests span both manufacturing process and material science. Much of his work has been on improving the understanding, manufacturing, material processing, mainly through the application of casting of magnesium alloys and aluminum alloy, shaping such as cold roll forming and hot forging. In the roll casting of magnesium alloys, he has worked on characterizing the casting of rapid cooling of magnesium alloys by twin-roll casting. He is now the chair of the Japan Association of Aluminum Forging Technology. He has published a lot of research papers in journals and conducting works relating materials processing technology of light metals, such as aluminum and magnesium alloys.
Title of Speech: Improvement of Room Temperature Formability of Twin-Roll Cast Magnesium Alloy by Adopting Repeated Bending and Heat Treatment
Abstract: Magnesium alloy has excellent specific stiffness among lightweight materials, so it is suitable as a material replacement for structural parts such as press-formed plate products. However, most magnesium alloy materials used in production was AZ91 for diecasting. In this paper, twin-roll cast Mg-9mass%Al-1 mass%Zn with 2 mass% Sn alloy was used for the purpose of fabricating for wrought magnesium alloy which can be bent at room temperatures. An appropriate solution annealing condition was investigated in order to reduce beta phase precipitation, which may cause cracking without coarsening of crystal grain size while for improving cold formability of twin-roll cast Mg-9mass%Al-1 mass%Zn-2 mass% Sn alloy.
The purpose of this study is to fabricate thin sheet plate for the practical use for plastic forming in the room temperature by using twin-roll cast Mg-9mass%Al-1 mass%Zn-2 mass% Sn alloy, which have possibilities to improve mechanical properties and corrosion resistance by applying heat treatment after twin-roll casting. Pre-strain to the solution treated twin-roll cast material was given and anealing was performed. A V-bending test has been conducted in order to eastimate cold fromability at room temperature.
A twin-roll cast material with a thickness of 2.4 mm and a width of 100 mm was prepared using Mg-9.0 mass%Al-0.72 mass%Zn-1.85 mass%Sn-0.21 mass%Mn (AZT912). After twin roll casting of AZT912, the twin-roll cast strip was solution heat treated. The solution-treated AZT912 twin-roll cast material was polished. The repeated bending process was performed by bending to a bending radius of R = 15 t using a three-roll bender. Then, the bending in the opposite direction to R = 15 t, and then annealing for 1 h in a hot press heated to 406 °C and heat distortion correction, and hot water quenching, the twin-roll cast AZT912 material was repeatedly bent twice will be referred to as AZT912 repeatedly bent material.
The cold formability of the fabricated AZT912 repeatedly bent material was improved by adopting repeated bending and heat treatment. As a result, it has been found that the limiting bent ratio, bent radius R and thickness t R/t was less than 2.0 at room temperature.