Microstructure in A356/AA6xxx after bimetallic casting with flux coating

Joint 5th International Conference on Advances in Solidification Processes;5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining

土木建筑工程;计算机科学

Opsal Bakke, Aina^1 ; Arnberg, Lars^1 ; Li, Yanjun^1

Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim, Norway^1

关键词: Chemical treatments;    Energy dispersive X ray spectroscopy;    Metallic bonding;    Metallurgical bonds;    Microstructure characterization;    Preheating temperature;    Solidification structure;    Wrought aluminum alloy;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/529/1/012024/pdf
DOI  :  10.1088/1757-899X/529/1/012024

来源: IOP

【 摘 要 】

This work focuses on bimetallic casting between A356 alloy melt and profiles of AA6xxx wrought aluminum alloys through a gravity casting process, with the aim to improve the component's mechanical properties. However, combining two aluminum alloys is difficult due to the stable aluminum oxide present on the surface of the aluminum inserts and the advancing liquid melt front. The oxide layer strongly reduces the wettability between aluminum melt and solid metal. It will also prevent diffusion and formation of a metallurgical bond. In order to obtain sound metallic bonding between the two alloys, different surface treatments, including flux coating and chemical treatments of the profiles have been tested. The influences of preheating temperature and melt flow modes on the quality of the bimetallic casting have been addressed. Based on a detailed microstructure characterization of the bonding layer in the casting, by using Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), the solidification structure development at the interface has been discussed. Results showed that when flux coating was applied, magnesium diffused to the insert surface and prevented formation of a metallurgical bond. Without flux coating, a metallurgical bond was achieved due to slight melting of the insert surface.