Prediction of the contact time through modeling of heat transfer and fluid flow in compound casting process of Al/Mg lig
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i Farzadi Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran 15875-1774, Iran
Seyed Reza Alavi Zaree Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz 61357-83151, Iran (Received 22 December 2016; accepted 13 March 2017)
In this study, the time that molten magnesium is in contact with the aluminum insert before solidification was predicted by solving the conservation equations of mass, momentum, and energy during compound casting of dissimilar Al/Mg couples. For this purpose, a three-dimensional transient model and FLOW-3D software were utilized and distributions of temperature and velocity vectors in the fluid over time were obtained. Then, the contact time at the bottom, middle, and top of aluminum insert in its interface with the magnesium melt was calculated. The results of simulation show that the contact time decreases from about 1.7 s at bottom to 1.6 s at middle and 0.8 s at top of the interface, respectively. This is consistent with the experimental metallographic observations which indicate a decrease in the thickness of formed intermetallic compounds from bottom to middle and top of the Al/Mg interface.
I. INTRODUCTION
Compound casting is one of the economic techniques used for producing different metallic couples.1–8 In this process two metallic materials—one in solid state, the other in liquid state—are brought into contact with each other. In this way, a diffusion reaction zone forms at the interface and joins two materials together.9 In the compound casting process, period for which the insert is in contact with the melt (contact time) is a very important parameter to achieve a good joining between two metals. When the contact time is too short, good bonding cannot be achieved while a long contact time can lead to melting of the insert or form extra harmful intermetallics at the interface. There are many factors that can affect the contact time, such as the volume ratio of the melt and the insert, size of the insert and cast, pouring temperature, preheat temperature, and gating system.2,10 Considering all these factors together for the prediction of the contact time is too difficult and needs so many try and error experiments. Heat transfer and fluid flow simulations can be helpful for estimating the contact time and hence the
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.113
state of bonding at the interface in the compound casting process. Few efforts have been performed to simulate the compound casting process. Noguchi et al.2,11 applied solidification simulation to predict the temperature distribution during compound casting of steel/cast iron couples. They examined different gating systems and found that the necessary contact time to achieve a good bonding between steel inserts and cast iron melts is 50–100 s. They also simulated the effect of sample size (with same volume ratio) on contact times for differ
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