가스아토마이징된 $Al_{87.3}misch$ $metal_{8.3}Ni_{4.4}$ 분말의 냉각속도와 수지상 가지 가격에 관한 고찰

A Study on Cooling Rate and Dendrite Arm Spacing of Gas Atomized $Al_{87.3}misch$ $metal_{8.3}Ni_{4.4}$ Powder

The present work is an attempt to evaluate the relationship between dendrite arm spacing and average cooling rate in gasatomized $Al_{87.3}misch$ $metal_{8.3}Ni_{4.4}$ powder by means of the following methods. One is calculation of heat transfer coefficient and average cooling rate, which are derived from estimated particle velocity during gas-atomization. The other is measurement of secondary dendrite arm spacing, which are observed on the particle surface. Then, we make experimental equation for this relationship in case of permanent mold casting and compare it with similar equation in case of rapidly solidified powder. Both average cooling rates and solidification rates are considered to represent the variance of dendrite arm spacings in two types soidification route. Even though there is a considerable difference in each average cooling rate, the dendrite arm spacing values are similar in two cases; particle diameter, $100\;{\mu}m$, and casting width, 2.05 mm. It is because that each solidification route has similar solidification rate.