Makoto Koizumi

Role of shear band in texture control of Al-Mg alloys

Shear bands formed in Al-Mg alloys during cold rolling are nucleated on grain boundaries. Their mechanism of formation is different from that already proposed in the case of single crystals of the same alloy. Since recrystallized grains of non-cube orientations are nucleated on these shear bands during annealing, the development of cube recrystallization texture can be strongly suppressed by enhancing shear banding during cold rolling. Control of shear band thus provides a new fundamental technological tool to improve drawability of Al alloy sheets. In a microscopic scale, deformation in grain boundary regions also plays here a very important role, as in the case of the formation of {111}uvw recrystallization textures in low carbon steel sheets.

Graded Material of Diamond Dispersed TiB2-Si Composite by SHS/Dynamic Pseudo Isostatic Compaction

A graded dispersion of diamond in TiB 2 /Si cermet (90vol% diamond layer diamond graded dispersed layers / matrix) was achieved by dynamic pseudo isostatic compaction (DPIC) just after self-propagating high temperature synthesis (SHS). The DPIC was performed using commercial casting sand as the pressure transmitting medium for the densification of the cermet. The process enabled to simultaneously synthesize and densify the cermet matrix within a few minutes. Diamond (an average particle size, approximately 30μm) mixed with the reactant was fixed in the matrix produced after the SHS. The maximum combustion temperatures were controlled to be approximately 2000 K to prevent the diamond to graphite transformation The diamond particles were found to be strongly fixed in the matrix even after lapping with a diamond abrasive by SEM. A simple calculation of residual stress based on the graded volume ratio of diamond in the matrix was also performed.

Formation of FGM Coating by the New Method of Thermoreactive Electrospark Surface Strenthening (TRESS)

This work describes the method of Thermoreactive Electrospark Surface Strengthening (TRESS) The physical essence the TRESS method is that the electrode presents a mixture of chemical reagents which can interact with each other on the substrate with a high heat evolution after a local heat initiation of the synthesis reaction by the electric discharge energy. Thus the process of coating formation becomes a less energy consuming one as compared to the basic technology of the electrospark alloying. The opportunities of TRESS method are exposed with the example of the FGM wear and heat resistant coatings formation on the base of NiAl, TiAl and its composites with carbides, borides and other solid fillers. The opportunity of FGM diamond containing coatings production by TRESS is presented. Masstransfer kinetics, coating structure and properties were studied.