Akira Ikenaga’s research while affiliated with Osaka Prefecture University and other places

In the expendable pattern casting (EPC) process for the aluminum alloy casting, the thermal decomposition rate of the expendable pattern is smaller than the cast iron, therefore the misrun by the temperature drop at the melt surface occurs easily. This study takes account of the control of the heat release to the mold to investigate numerically and experimentally the effect of the coat permeability on the molten aluminum alloy temperature during mold filling in the EPC process. An aluminum alloy plate was cast by the EPC process, and the temperature change of the melt surface to the melt flow direction was measured. The use of high permeability coat led to a higher melt velocity and a smaller temperature drop at the melt surface than the case of the normal permeability coat. The temperature of molten metal filling into the cavity was numerically simulated, and the obtained temperature drop at the melt surface agreed relatively well with the experimental values. [doi:10.2320/matertrans.M2011242]

Cast irons are thought to be superior in corrosion resistance to plain steels. The differences between cast iron and plain steel are mainly in the existence of graphite and the amount of silicon. The graphite nobility for the matrix results in the electric potential difference between graphite and matrix. Thus the study of the effect of graphite morphology on corrosion resistance in cast irons under mild corrosive environments is needed. In this study, ductile cast irons with different graphite nodule size are austempered, their corrosion potentials are measured and their anodic polarization tests are carried out in 0.01N HCl aq. . The results show that : (1) In ductile cast irons, the smaller is the graphite nodule size, the lower is the corrosion resistance. In ADI, however, the graphite nodule size has a littIe effect on the corrosion resistance. (2) In ADI, the amount of retained austenite and the corrosion resistance decrease as the austempering time increases.

Four flaky graphite cast irons of different graphite structures with a pearlitic matrix were prepared to clarify the graphite structure's influence on the dry sliding wear property. Two melts of cast iron with different carbon contents were solidified at two different cooling rates. The four resultant samples had type A flaky graphite or type D eutectic graphite structure with different graphite volume fractions and fully pearlitic matrixes. A pin on the disc type wear test evaluated the four samples' dry sliding wear properties. Results showed that the type D graphite structure wore down faster than the type A graphite structure did. The type of graphite morphology influenced the specimen wear rate as strongly as the graphite volume fraction did in flaky graphite cast irons of this experimental range.

The effective surface treatment method for steel insert composited with Al base metal by expendable pattern casting (EPC) process and the bonding interface between steel insert and Al base metal were investigated. It was found that Zn plating on steel insert was effective on improving the bonding property between steel insert and Al base metal in EPC process. Zn is thought to promote the formation of diffusion layer. But almost none content of Zn was observed in the boundary which had been plated on the steel insert. A diffusion layer consisting of Al, Si and Fe was formed at the insert/alloy interface and its hardness was higher than the steel insert as matter of course Al base metal. This layer turned out to be intermetallic compounds of Al-Si-Fe system. Higher pouring temperature promoted the diffusion of Fe into Al alloy, so Fe content in intermetallic layers increased at higher pouring temperature. The layer nearest to steel disappeared due to applied pressure.

We focused on the surface reinforcement of ligth weight casting alloys with Ni-Al intermetallic compounds by in-situ combustion reaction to improve the surface properties of non-ferrous casting components. In our previous works, green compact of elemental Ni and Al powders were reacted to form Ni 3 Al intermetallic compound by SHS (Self-propagating high temperature synthesis) reaction with the heat of molten Al alloy and simultaneously bonded with Al casting alloy. But some defects such as tiny cracks and porosities were remained in the reacted compact. So we applied pressure to prevent thermal cracks and fill up the pores with liquid Al alloy by squeeze casting process. The compressed Al alloy bonded with the Ni 3 Al intermetallic compound was sectioned and observed by optical microscopy and scanning electron microscopy (SEM). The stoichiometric compositions of the intermetallics formed around the bonded interface and in the reacted compact were identified by energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). Si rich layer was formed on the Al alloy side near the bonded interface by the sequential solidification of Al alloy. The porosities observed in the reacted Ni 3 Al compact were filled up with the liquid Al alloy. The Si particles from the molten Al alloy were detected in the pores of reacted Ni 3 Al intermetallic compact. The Al casting alloy and Ni 3 Al intermetallic compound were joined very soundly by applying pressure to the liquid Al alloy.

Applying brittle intermetallic compound coating on metals can enlarge the range of their use. In this instance, the properties of the coating layer are influenced by the constituent phases of intermetallic compound coating layer.In this study, the mixtures of Ni and Al powder have been reacted at different heating rates in an induction furnace in order to obtain the intermetallic compound coating layer with a single phase structure on a ductile cast iron. The microstructures and mechanical properties of the coating layer are investigated and the effects of heating rate in the induction furnace on the properties of intermetallic compound coating layers are evaluated.It was found that the ignition temperature and the maximum temperature increase significantly with increasing heating rate. It was also found that the coating layer is composed of single phase NiAl corresponding to the initial composition of mixed powder and adhesion qualities with substrate are improved with increasing heating rate.

[ ], is a well-known metal sulfide applied as solid lubricants and an additive to prolong the life of sintered bearings under severe conditions. However, the high price of limited its wide application. This study is aimed to investigate the possibility far application to solid lubricants for as a substitute of . Bronzes added and , are produced by powder metallurgy in this study, and then evaluated their friction and wear properties., as well as sintered bronze. The sliding wear test using pin-on-disc type machine, was conducted at several sliding speeds for three type test pieces sintered bronzes added and , and sintered bronze without lubricants. Addition of to bronze leads to relatively good friction properties, although it is not so good as addition of . However, the wear properies of sintered bronze added are better than that of sintered bronze added .

Combustion synthesis coating layer of Ti-Al based intermetallic compounds was produced onto a spheroidal graphite cast iron substrate using high frequency induction heating. This paper examines the influence of various heating rates on the combustion synthesis reaction, and evaluates the microstructure, adhesive strength, hardness and wear resistance of the coating layer. The heating rate was found to have a great influence on the combustion synthesis reaction. A large amount of Ti-Al intermetallic compounds formed in the coating layer at the higher heating rates tested, while the unreacted phase abounded at a lower heating rate. Fully-densified coating layers with good adherence to the substrate formed and diffusion layers were observed at the bonding interface in the entire specimens. The high adhesive strength of the coating layer needed appropriate thickness of the diffusion layer, which indicated that the adhesive strength of the coating layer closely related to the heating rate. All coating layers exhibited higher hardness and more excellent wear resistance than the substrate. In addition, the hardness and wear resistance of the coating layer improved at a high heating rate.

The effects of alloying elements on the as-cast microstructures and mechanical properties of heavy section ductile cast iron were investigated to develop press die material having high strength and high ductility. Measurements of ultimate tensile strength, 0.2% proof strength, elongation and unnotched Charpy impact energy are presented as a function of alloy amounts within 0.25 to 0.75 wt pct range. Hardness is measured on the broken tensile specimens. The small additions of Mo, Cu, Ni and Cr changed the as-cast mechanical properties owing to the different as-cast matrix microstructures. The ferrite matrix of Mo and Ni alloyed cast iron exhibits low strength and hardness as well as high elongation and impact energy. The increase in Mo and Ni contents developed some fractions of pearlite structures near the austenite eutectic cell boundaries, which caused the elongation and impact energy to drop in a small range. Adding Cu and Cr elements rapidly changed the ferrite matrix into pearlite matrix, so strength and hardness were significantly increased. As more Mo and Cr were added, the size and fraction of primary carbides in the eutectic cell boundaries increased through the segregation of these elements into the intercellular boundaries.

A magnesium alloy was adopted to an evaporative pattern casting (EPC) process to combine advantages of each. In the present study, foam patterns were cast at a top gating system under atmospheric and reduced pressure to evaluate casting characteristics of AZ91D to develop a complete EPC process for high productivity of magnesium alloy castings. Filling time and temperature of molten metal were measured during mold filling. It was recognized that the average filling velocity was affected by the difference of the coating material and the degree of reduced pressure. The grain size of the magnesium alloy was slightly dependent on the degree of reduced pressure. It was considered that the application of the high reduced pressure, which changed the shape of melt surface from convex to concave, was related to the occurrence of internal defects such as cold shut laps or folds in the casting.