84th Magnetic Materials Center Seminar
August 20, 2008, 9:00-
7th floor small seminar room, Sengen
Microstructure and Mechanical properties of Al-Zr nanocomposite produced by mechanical alloying and spark plasma sintering
B. S. Rao
High strength Al-base alloys has become a great deal of interest because of their good strength to weight ratio and good corrosion resistance. Al-Zr alloys were studied to realize a high-strength with good plasticity values. At first nanocrystalline Al was produced with different zirconium content (2.2, 3, 4 and 4.7 at.%) through mechanical alloying and subsequently sintered with spark plasma sintering technique. Mechanical properties of these materials were tested in compression mode at room temperature. A compressive strength value of 1GPa with a plasticity of 10% was obtained. Detailed microstructure characterization has been done with the help of scanning electron microscopy as well as electron microscopy.
The microstructure consists of nanocrystalline Al with a grain size of 50 to 100nm with Al3Zr (L12) phase having a size of 50 to 70nm distributed along the grain boundaries and coarse grain Al-phase at the particle boundaries was formed. The high strength of the current alloy was due to nano-grain structure and reasonably good plasticity was due to the presence of coarse grain Al-phase.

Local structure analysis of amorphous by nano-beam diffraction
T. Ohkubo
In order to analyze amorphous structure, X-ray and neutron diffraction techniques are commonly used. However both techniques can get only averaged information. Therefore, if the scale is nano-meter size, it is impossible to analyze by such methods. In functional devices, nano-scale amorphous structure often appears. When we need to analyze such nano-region, nano-beam diffraction analysis is very useful. In this talk, I will explain what the bases are, what the procedure is, what the limit is, what the demerits and merits are.

Microstructure characterization of HDDR processed Nd-Fe-B powders with different DR time
H. Sepehri Amin
The controlled hydrogenation decomposition desorption recombination (HDDR) is a well known method to produce anisotropic Nd-Fe-B magnet powders. It is proved that the different parameters of HDDR procedure affect inducement of anisotropy and increasing of magnetic properties of these powders. Change of specific properties of these magnets can be determined by their microstructure. In tomorrow seminar, the reason of coercivity increscent of Nd-Fe-B HDDR powders with different desorption recombination time using microstructure characterization will be presented.