The effects of cooling profiles immediately after solution treatment on the state of solute elements in JIS AC4CH aluminum casting alloys were investigated. Three types of specimens (L.C., A.C.1, and A.C.2) with different cooling profiles in the temperature range from 560℃ to 250℃ were prepared. The L.C. specimen was cooled under a constant rate of about 6.5℃ /s. On the other hand, the A.C.1 and A.C.2 specimens were cooled with a high cooling rate in the high temperature region and a low cooling rate in the low temperature region. There were no clear differences in hardness and electrical conductivity after cooling at the indicated conditions among the three specimens. Changes in hardness and electrical conductivity during the artificial aging treatment and DSC curves suggested that the A.C.2 specimen has a larger amount of solid solution atoms than the L.C. specimen. Observation using SEM revealed that the formation of precipitates during cooling differs depending on the cooling profiles. Rod-like precipitates measuring several tens of nm in diameter and several hundreds of nm in length were observed in the second dendrite (DAII) for the A.C.2 specimen. In the primary dendrite (DAI), granular-precipitates measuring several tens of nm in diameter were observed together with the rod-like precipitates detected in the DAII. In the L.C. specimen, however, only the rod-like precipitates were observed in both the DAI and DA II. The number density of the rod-like precipitates of the L.C. specimen was smaller than that of the A.C.2. These differences in the precipitation state are thought to be due to the amount of solid solution atoms and the cooling rate in the temperature range causing the formation of each precipitate.

  This research aimed to evaluate the erosion-corrosion resistance of lead-free copper alloys depending on the flow rate of the test solution using jet-in-slit tests. JIS CAC411 and JIS CAC804 were used as lead-free copper alloy specimens. JIS CAC703, JIS C3771, and JIS CAC406, which are conventional valve materials, and pure copper were also tested. The results were described as follows : In case of JIS CAC411 and JIS CAC406 which have higher Sn concentration than the other specimens, the damage depth by erosion-corrosion was smaller than those of the other copper alloy specimens, and hardly increased with increasing flow rate of test solution. In case of JIS CAC804, erosion-corrosion occurred around the center of the specimen, and the damage depth increased with increasing flow rate. However, the damage depth on the outside of the specimen was more or less independent of the flow rate except for 0 L·min-1. The damage depth of JIS C3771 on the outside of the specimen was almost independent of the flow rate in the same way as JIS CAC804, when the flow rate was lower. For both the JIS CAC703 and Cu specimens, the damage depth at the center and on the outside of the specimen severely increased with increasing flow rate.

  The purpose of this study was to investigate the effects of melting at temperatures higher than the AIP crystallization temperature on the microstructure in hypereutectic Al-Si alloys containing phosphorus in the range of 0.001 to 0.008%. Al-17%Si-0.004%P alloy was used as one of the experimental alloys. The experiment included melting 6kg of the alloy at 1473K in a high-frequency induction furnace, holding the melt for 20min, casting it into a steel mold by gravity casting, remelting the gravity die castings at 1023K in a electric furnace, and casting the melt into a steel mold by gravity casting. As a result of this experiment, it was found that the high temperature melting and the addition of phosphorus resulted in the refinement of both the primary and eutectic silicon.