AA-TP1 (Standard Test Procedure for Aluminum Alloy Grain Refiners; TP-1 test) is one of the evaluation tests of aluminum grain refiner. Although it is the most well-maintained test at present, it is not easy to perform the test by academic institutions because it requires a large amount of molten metal. In this study, we propose new evaluation method of grain refining performance of aluminum cast using TP-1 test mold. Effects of temperature of molten metal, holding time after addition of refiner (Al-5%Ti-1%B) and preheating temperature of the mold for microstructure of as-cast pure Al were examined. Obtained results were compared with the microstructure obtained by conventional TP-1 test.

The casting defects such as shrinkage porosities and hot tears are reduced by grain refinement in cast products. The Al-Ti-B grain refiner is added to the molten aluminum during casting process to achieve the fine grain structure. The Al-Ti-B grain refiner shows good grain refinement effectiveness, however the risk of increase the inclusions involve. Therefore, it is required to reduce the usage of grain refiner. The optimization of the usage of grain refiner is difficult, because the inoculation efficiency fluctuates with the manufacturer, content and lots. Free growth model, which is proposed by Greer, suggested the TiB₂ particle size distribution is one of factors that change the inoculation efficiency. On the other hand, the effect of particle size distribution have not been verified in experimentally and calculation by using multiple grain refiners. In this study, a grain size prediction model was developed to clarify the cause of variation of inoculation efficiency. The calculation results were compared with experimental data which was obtained by TP1 test.

This paper proposes a technique for evaluating the nucleation sequence and grain refinement phenomena during solidification of a metallic alloy. Time-resolved and in-situ transmission imaging using a monochromatized X-ray in a synchrotron radiation facility, SPring-8, showed wave-like nucleation events, in which nucleation sequentially occurred along the temperature gradient, in an Al-4mass%Si alloy with addition of TiB₂ (Al-3mass%Ti-1mass%B alloy). The position and time of nucleation events were measured to analyze the nucleation wave. The wave motion, which was calculated from the measured data, was used to evaluate the difference of nucleation temperature for each dendritic grain from the wave front. The standard deviation of the temperature difference in the Al-4mass%Si alloy with TiB₂ particles was evaluated to be as small as 0.25 K. The addition of TiB₂ reduced the standard deviation to more than one tenth. This study shows that the dispersion or the standard deviation is a representative figure for evaluating the potency of nuclei.

Phase diagrams and thermodynamic properties of KCl-KF, KCl-AlCl₃, KF-AlF₃, KCl-KF-AlF₃ systems have been analyzed based on the experimental data. The Gibbs energies of the liquid and halite phases were approximated with the two-sublattice model for ionic liquid and crystal, respectively. The Gibbs energies of other phases were approximated by the line compound model. Most of the experimental information could be reproduced by the present set of thermodynamic parameters. This set of parameters can be predicted from the phase equilibria and thermodynamic properties at full range of composition in KCl-KF-AlF₃ system.

It is well known that inclusions in molten aluminum cause defects such as cracks. In order to remove such inclusions, it is important to understand the behavior of inclusions in the melt. In present study, a water model experiment on pseudo heterocoagulation, for example, collision between flux and inclusions was performed in turbulent condition. The experimental results were compared with the model calculation results to analyze the heterocoagulation behavior. As a result, the model calculations for heterocoagulation agreed with the experimental values on change in particle number density with time. Furthermore, it was suggested that heteroaggregates were preferentially produced when the particle size ratio between different particles was small. On the other hand, it is difficult to generate heteroaggregates because the coagulation coefficient decreases in the case of large particle size ratio.

Extremely low levels of hydrogen concentration in molten aluminum cast alloy has been required for the production of high-performance alloys. AC2B (Al-5.0～7.0mass%Si-2.0～4.0mass%Cu) alloy, which is one of the typical aluminum casting alloys, is mainly used for the automobile industry. It is expected that vacuum treatment of molten alloy can lead to small oxidation loss of metal and excellent hydrogen removal. In order to clarify the hydrogen solubility and removal mechanism of vacuum degassing, hydrogen concentrations of AC2B alloy after hydrogen injection at the temperature of 973 to 1123K and vacuum treatment of 5×10² Pa at 1023K were investigated in this study. It was found that hydrogen solubility of molten AC2B aluminum alloy can be described by the following equation:

log(S(cm³/100g-Al))=1/2log(p_H2(mmHg))-4891/T(K)+3.165

An A1050 aluminum sheet was collided against a steel mold with a small V-shaped through-thickness groove by magnetic pulse forming (MPF), and the deformation structure was investigated. The local changes in strain rate,strain and temperature during MPF were investigated by using a series of numerical analyses. Almost no change in grain morphology was observed at the mid-thickness area of the sheet. In contrast, an extremely large intensive deformation occurred at the aluminum sheet surface located in the groove. The ultrafine grains of several to several tens of nanometers were observed on the surface of the aluminum sheet. The changes in strain rate, strain and temperature were also investigated by using ANSYS AUTODYN. The simulation results revealed that the sheet flew into the groove at an extremely high local strain rate exceeding 10⁷ s^‒1. Furthermore, a large temperature increase exceeding 1000 K at the sheet surface was estimated by the simulation. The cooling process was also reproduced by OpenFOAM. It was revealed that the rapid cooling of 10⁸～10⁹ K/s order occurred on the sheet surface. It is considered that the ultrafine grains observed at the sheet surface resulted from the local melting and the successive rapid cooling.

Stress Corrosion Cracking (SCC) of magnesium alloys is commonly observed in corrosve environments such as NaCl solutions. In this paper, the effect of aluminum content on SCC of magnesium alloy ingots, AM60B and AZ91D, is evaluated using Slow Strain Rate Testing (SSRT) in two environments: (1) air and (2) 5%NaCl solution controlled from pH10 to pH11 with Mg (OH）₂. The result shows that AM60B is less susceptible to SCC than AZ91D. In AZ91D specimens, accelerated corrosion is observed around Mg₁₇Al₁₂ compounds in microstructures adjacent to the fracture surface. To investigate the relationship between Mg₁₇Al₁₂ compounds and this susceptibility to SCC, heat treatment was applied to AZ91D and the solution-treated AZ91D specimen showed the same susceptibility to SCC as the as-cast specimen of AM60B alloy ingot. However, at peak-age condition, AZ91D specimen showed a 22% higher susceptibility to SCC than the as-cast AZ91D alloy ingot. Consequently, susceptibility to SCC of the Mg-Al alloys tested in the 5%NaCl solution, is found to depend on the amount of their Mg₁₇Al₁₂ compounds.

Porous aluminum includes a large number of pores inside its base material. Sintering and dissolution process are among the process in the fabrication of porous aluminum which has open-cell structures. The pore size and porosity of porous aluminum can be easily controlled by sintering and dissolution process. The shape of sodium chloride (NaCl) is transferred to the pores. In this study, granular NaCl was used as the spacer. It was shown that granular NaCl was necessary for fabricating porous aluminum. In addition, the removal time of NaCl was markedly shortened when using granular NaCl compared with that when using general crystalline NaCl.