Die casting, a highly efficient production method, is widely applied to the manufacturing of automotive components. On the other hand, extending the die life is required to meet the needs of ...reducing the production cost because die costs are included in the manufacturing costs. As one of the primary factors leading to die failures, soldering was investigated in this study by observing the adhesion of ADC12 alloy to the die and the reaction between ADC12 alloy and die in die casting process, analyzing the diffusion of concerned elements in ADC12 alloy, and numerically simulating the flow and the solidification of the molten metal. It was revealed that ADC12 alloy adhered to the surface of the die and caused the surface layer of the die castings to remain on the surface of the die by breaking the die castings with shearing stress at the time of ejection. In addition, Al-Si-Fe compounds were found at the interface between the die and the remaining ADC12 alloy layer with the repetition of die casting. These compounds grew gradually with the concentration of Si in the remaining ADC12 alloy layer towards the interface by diffusion with the further increase of shot numbers.
Die-casting is widely applied to the production of automotive components because of its high productivity for manufacturing complex-shaped castings. However, since molten metal is injected into a ...cavity at high speed and it solidifies rapidly under high pressure in this process, many casting defects are liable to occur. Although the most frequent internal defect is gas entrapment, shrinkage porosity also forms in the thick-wall portions of die castings. In order to avoid shrinkage porosity, there is a need to feed adequate molten metal to compensate the shrinkage volume during solidification. Therefore, it is desirable to better understand the feeding behaviors of molten metal under high pressure and rapid cooling conditions in the die casting process. In this study, the permeabilities of Al-Si alloys during the solidification process under die-casting conditions were determined by measuring the pressure transmission of the molten metal from the plunger to the mold cavity so as to obtain the feeding resistance coefficients. The formation of shrinkage porosities in die-castings was proven to be predictable by numerical simulation using the obtained feeding resistance coefficients.
The size of defects in castings affects mechanical properties such as fatigue strength. These properties are the most important properties used for designing aluminum alloy casting components, and ...usually increase with decreasing size of internal defects. Large internal defects mainly form due to the volumetric shrinkage of melt at the last solidified position. In this study, we therefore examined the possibility of generating microbubbles in aluminum alloy melts for dispersing internal defects in castings. Ultrasonic treatment was used for generating nitrogen or argon microbubbles in the melt and was found to be suitable for forming fine gas porosities dispersed in castings. The fine gas remained in the melt for 3600 s, and the generated argon gas was detected from the porosities in the castings. The ultrasonic treatment could also remove inclusions and hydrogen in the melt. Moreover, the fine gas porosities in castings did not decrease the tensile strength of the castings.
To elucidate the segregation behavior of solutes in Al-Si and Al-Cu binary alloys, specimens of several hypo-eutectic Al-Si alloys water-quenched at different stages of solidification or air-cooled ...from melt to room temperature were prepared and the distributions of Si concentration were analyzed across the primary dendrites. The Si distribution in the dendrites of the specimens water-quenched during primary solidification showed that Si concentration declined from the surface toward the center of the dendrite. In contrast, the specimens water-quenched after eutectic solidification or air-cooled from melt to room temperature showed that Si concentration increased from the surface toward the center of the dendrite. The diffusion distance of Si in the dendrites during the cooling process from the finish of solidification to room temperature was calculated according to Fick's second law and showed good agreement with the measured value. Therefore, the segregation behavior with high Si concentration in the center of the dendrite was attributed to the diffusion of Si from the center to the surface of the dendrite, resulting in the precipitation on the adjacent Si phase during eutectic solidification.
Capillary shaping is a novel manufacturing technique for obtaining complicated shaped aluminum frames used for optimizing weight and design of car body structure. This process requires faster ...pulling rate for higher productivity and mechanical properties. However, strong air cooling causes breaking of the melt column which results in the interruption of the pulling process. In this study, we carried out water model experiments and capillary shaping of cylindrical specimens under strong air blowing conditions for investigating the mechanism of the melt column breaking. We found that melt column braking occurred due to negative pressure arising from air blowing in the hollow specimens. We successfully increased the pulling rate using strong air cooling under controlled air pressure in the hollow specimens.
We have developed a new laser ablation type cluster source named `spatiotemporal confined cluster source' (SCCS), which gives well-defined thermo-dynamical conditions for cluster growth with narrow ...size dispersion. A laser-induced shock is controlled to produce a definite mixed gas layer of the silicon vapor and helium gas, which is locally confined in a sub millimeter space, and conserved densely for a time of 160 μs. The generated silicon clusters, which are ionized by an ArF excimer laser for mass analysis without dissociation, show narrow size dispersion with characteristically higher abundance of stable Si
23H
x
(46%), Si
19H
x
(14%), and Si
21H
x
(12%) clusters.
Solid solution elements in the α-Al phase affect dimensional precisions under high temperature circumstances and the mechanical properties of Al-Si alloy castings. However, there is insufficient ...information on the concentration of the solid solution elements in as-cast castings. In this study, we examined the possibility of estimating the concentration of solid solution silicon in the α-Al phases of permanent mold cast Al-Si alloy castings using a theoretical model related to the concentration of the solid solution silicon and the dimensional change arising from heat treatment. Al-1%Si and Al-10%Si alloy castings containing 1.00% and 1.06% solid solution silicon in the α-Al phases, respectively, were prepared for the examination by solution treatment at 805K for 3.3 hours after casting. By comparing the experiment and theoretical dimensional changes of the specimens, it was verified that the theoretical model can be used for calculating the concentration of solid solution silicon in the α-Al of castings. The average concentrations of the solid solution silicon in the α-Al phases of as-cast Al-1%Si and Al-10%Si alloy specimens were also estimated as 0.81% and 0.73% respectively from the dimensional changes of the castings due to heat treatment at 743K, 713K and 473K by the theoretical model.
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