Yoshimi Watanabe is currently a Professor of Engineering in the Department of Physical Science and Engineering at Nagoya Institute of Technology. He earned a Bachelor of Engineering in Metallurgical Engineering from Nagoya Institute of Technology in 1985, Master of Engineering in Materials Science and Engineering from Tokyo Institute of Technology in 1987, and a Ph. D. in Materials Science and Engineering from Tokyo Institute of Technology in 1990. After that, he worked at Kagoshima University as a research associate at the Department of Mechanical Engineering from 1990 to 1992, at Hokkaido University as a research associate at the Department of Metallurgical Engineering from 1992 to 1995, at Shinshu University as an associate professor at the Department of Functional Machinery and Mechanics from 1995 to 2005. In 2005, he moved to Nagoya Institute of Technology as a full professor. He was worked at Lawrence Berkeley National Laboratory as a visiting scientist from 1997 to 1998. His current research interests are functionally graded materials (FGMs), grain refiner of cast aluminum, metallic 3D printing, severe plastic deformation, Fe based shape memory alloy.
Abstract: It is well accepted that an effective refiner contains heterogeneous nucleation site particles having a smaller lattice mismatching with the metal matrix. It is known that alloying with a certain amount of a transition element, Me, such as Cr, Mn, Fe, Co, Ni, Cu, or Zn causes the transformation from the D022-type tetragonal structure of Al3Ti into a high-symmetry L12 cubic structure. This transformation increases the symmetry of Al3Ti intermetallic compounds. Moreover, by changing the alloying element, the lattice constant of the L12 modified (Al1-xMex)3Ti intermetallic compounds is controllable. In our previous studies, it has been shown that L12 modified (Al1-xMex)3Ti intermetallic compounds show good grain refining performance, since L12 modified (Al1-xMex)3Ti intermetallic compounds have a smaller lattice mismatching with the metal matrix. In this study, our recent results on grain refining performance of Al-Al2.5Cu0.5Ti, Al-Al2.7Fe0.3Ti and Al-Al2.7Ni0.3Ti refiners will be reviewed.
The L12 modified (AlxMe1-x)3Ti intermetallic compound particles (Me = Cu, Fe and Ni) were spark plasma sintered (SPSed) with pure aluminum particles. The grain refining performance of obtained Al- L12 modified (AlxMe1-x)3Ti refiners were studied. It is found that the smaller grains are observed for the aluminum casts fabricated with the Al- L12 modified (AlxMe1-x)3Ti refiners. Therefore, the L12 modified (AlxMe1-x)3Ti particles can act as effective heterogeneous nucleation sites for primary aluminum in the solidification.