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The factors influencing the preparation of silica glass coating on the brass substrate and the effect of coating on the undercooling and the structure of Al-12.5%Si alloy have been investigated. It is shown that a uniform sel-gel coating can be formed on the brass substrate when the molar ratios of H2O and ethanol to TEOS are higher than 7-8, the molar concentration of HC1 in the sel is lower than 6 × 10 ~4 and the withdrawal rate of the brass substrate from the sel is lower than 5 mm/s. The temperature for changing sel-gel coating to glass coating is 360℃ . The effects of silica glass coating on the degree of undercooling and the structure of Al-12.5 % Si alloy depend on the melt state. The silica glass coating does not influence the undercooling and structure of alloys with lower undercooling tendency; while this coating can gain the undercooling and refine the structure of the alloys with higher undercooling tendency.
The factors influencing the preparation of silica glass coating on the brass substrate and the effect of coating on the undercooling and the structure of Al-12.5% Si alloy have been investigated. It is shown that a uniform sel-gel coating can be formed on the brass substrate when the molar ratio of H2O and ethanol to TEOS are higher than 7-8, the molar concentration of HC1 in the sel is lower than 6 × 10 ~ 4 and the withdrawal rate of the brass substrate from the sel is lower than 5 mm / s. The effects of silica glass coating on the degree of undercooling and the structure of Al-12.5% Si alloy depend on the melt state. The silica glass coating does not influence the undercooling and structure of alloys with lower undercooling tendency; while this coating can gain the undercooling and refine the structure of the alloys with higher undercooling tendency.