Al-5Zr中间合金初生Al3Zr相三维形貌及其对浇注温度的依赖性

Three-Dimensional Morphology of Primary Al3Zr Phase in Al-5Zr Master Alloy and Its Dependence on Pouring Temperature

摘要:

采用熔盐反应法制备了Al-5Zr中间合金并利用强碱腐蚀获得了初生Al3Zr相的三维形貌，分析了Al3Zr相的长大机理，研究了降温过程中浇注温度（1 250、1 050、950、800 ℃）对合金中初生Al3Zr相三维形貌、尺寸及数量的影响，利用JMatPro软件和面积法分别计算了Al-5Zr中间合金的理论固相率和实际固相率。结果表明：Al-5Zr中间合金中Al3Zr相的三维形貌呈现厚板状、薄片状、花瓣状及搭桥状形貌，这些形貌的形成可以追溯到二维晶核和成分过冷综合作用机制。随着浇注温度降低，Al3Zr相形貌由薄片状逐渐转化为厚板状，薄片相尺寸减小、数量减少；厚板相尺寸增大、数量增多，两种形貌相的总数量减少。利用JMatPro软件计算合金的理论固相率与面积法计算合金的实际固相率基本吻合。从合金固相率看，随着浇注温度降低，厚板Al3Zr相的相对含量增多。

Abstract:

The Al-5Zr master alloy was fabricated by direct melt reaction technique in the Al-K2ZrF6 system. Three-dimensional morphologies of the primary Al3Zr phase in Al-5Zr master alloy were acquired by the alkali corrosion and their formation mechanisms were analyzed. The effects of pouring temperature (1 250, 1 050, 950, 800 ℃) on the morphology, size and the amount of primary Al3Zr phase in the cooling process were investigated. The theoretical and experimental values of solid fractions were calculated by JMatPro software and area-method, respectively. The results show that the morphologies of Al3Zr phase in the master alloy display thick-plate, thin-flake, petal and cross-bridge shapes; and the formation of these morphologies are resulted from two-dimensional nucleus growth and constitutional supercooling. With the decrease of pouring temperature, the morphologies of Al3Zr phase are changed from thin-flake to thick-plate, the size and the amount for the thin-flake phase decrease, while the size and the amount for the thick-plate phase increase, but the total amount of Al3Zr phase reduces. The theoretical value of solid fraction agrees well with experimental value. With the decrease of pouring temperature, the relative content of thick-plate Al3Zr phase increases in terms of the solid fraction.