Dual-Alloy Sand Mold Casting: Main Principles and Features

Abstract

The multi-material injector casting (MMIC) process allows the production of castings with two different alloys in a single process. The metal is introduced into the mold through a ceramic down sprue (injector) that moves with the rising surface of the melt. This results in a beneficial temperature distribution in the casting with enhanced filling and feeding properties. Combining two alloys in one casting affects the chemical composition, microstructure, and mechanical properties, which differ from those of the original alloys. The main goal of producing the dual-alloy castings is to adapt the alloy locally in the mixing zone according to the application needs. The original composition and characteristics of both alloys have to be ensured as much as possible. This article discusses the peculiarities of dual-alloy sand mold casting, considering the oxidation processes of the components under different conditions and the microstructure of the resulting ingots. The results of thermodynamic simulation, experimental dual-alloy sand mold casting, chemical composition, and macrostructure of the resulting castings are given in the article. The following factors have been investigated: the method of pouring two alloys (AlSi12 and AlSi9Cu3), which simulate two injector positions; the time between pouring each alloy (60, 90, and 120 s); the influence of a directional solidification with the bottom chill. The mixing zone was identified by the changes in the content of Cu measured by spark spectroscopy and EDS.