Prof. Hisaki Watari
Tokyo Denki University, Japan
Biography: Hisaki Watari has received his PhD in Mechanical System Engineering, from Gunma University, Japan in 2006. He has been researching into properties of magnesium alloy by rapid cooling by using twin roll casting in these fifteen years in Gunma University and Oyama National Colleague of Technology in Japan, in UMIST in the UK. He is now the chair of the Japan Association of Aluminum Forging Technology. He has published more than 130 papers in journals and conducting works relating metal forming of light metals, such as aluminum and magnesium alloys.
Speech Title: Future possibilities of Magnesium alloys in the transportation industry
Abstract: A total weight reduction approach has been a key issue for car manufacturers to cope with more and more stringent requirements for the protection of the planet. In recent years, production of magnesium alloy sheet still remains at a very low level, although production of magnesium has risen dramatically. The aim of the study is to confirm future possibilities of practical use of magnesium alloys by using hot forging technology to manufacture alloy producs, which will contributes to dramaticlally reduce proidust CO2 emission. Characteristic feature of hot forging of twin roll cast magnesium alloys which have relatively high aluminium content has been investigated. High tensile strength magnesium alloys containing 9 to 12% aluminum, such as AZ91, AZ101, AZ111, and AZ121 have been developed by rapid cooling process using a horizontal twin roll caster. A new experiment was performed for hot forging of high strength magnesium alloys with high aluminum content. From the results, using magnesium alloys with high aluminum content yielded less compressive deformation resistance than conventional magnesium alloys. It was also demonstrated that hot forging of magnesium alloys with high aluminum content produces small magnesium crystals (about six micro meters) and crystallized substances. The mean grain size of the microstructure of AZ121 forged at 623K was less ten micrometers although that of the AZ91 was about thirty micrometers. The small beta phase which precipitates in the twin roll cast AZ121 was distributed uniformly comparing to AZ91. Microscopic observation of the forged products, it has been cralified that the Hall-petch rule between mean grain size of forged materials and Vickers hardness has been proved. The effects of the dynamic recrystallization on the microstructures of the twin roll cast products has been disucussed. It has also been clarified that high aluminium content magnesium alloys could be used for original materials for hot forging. It has been found that the effects of aluminum content affects pricipitaion of beta phase as well as grain size.