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TESTING 1-2-3


The Impact of Chill Materials on Solidification and Physical Properties


A team of researchers investigated whether the benefits of composite chills in aluminum castings outweigh the added design complexity. A MODERN CASTING STAFF REPORT


reduce shrinkage porosity. Chill materials such as aluminum, copper and iron are chosen to maximize specific mechani- cal and microstructural properties. For example, though iron and copper have similar heat capacities, copper’s sig- nificantly higher thermal conductivity leads many casting engineers to use it in chills for casting areas that require more aggressive chilling capabilities. In an effort to quantify such differ-


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1 2 3


ences, a team of researchers compared the ADDING IT ALL UP Breaking down the latest research is as easy as 1-2-3.


“Effect of Different Chill Materials on Aluminum Casting Solidification and Mechan- ical Properties”Steve Robison, AFS, Schaumburg, Ill.; Stephen Gonczy, Gateway Materials Technology, Mt. Prospect, Ill.; Kai Hartman, Denison Industries, Deni- son, Texas; Robin Foley, University of Alabama, Birmingham, Ala.


Background—Chill materials are chosen to maximize certain mechanical and microstructural properties. Copper has high thermal conductivity, so it often is used to chill casting areas that require high heat extraction. The researchers compared the effects of iron and aluminum-copper chills on a set of uniformly produced castings. Procedure—The aluminum plates were cast with two sections with different thicknesses. Test bars from 1-in. and 2-in. thick sections were evaluated to assess the effects of the chills. The broken bars were evaluated for elonga- tion values, ultimate tensile strength, yield strength and secondary dendrite arm spacing. Results and Conclusions—There was little difference in the mechanical properties between the two chills. The composite chill provided somewhat higher elongation values. However, since the ultimate tensile and yield values were comparable, the differences in the two chills were insignificant and out- weighed by the potential added complexity related to composite chills.


etallic chills are commonly used in the produc- tion of aluminum castings to control solidification and


final mechanical properties and micro- structure of aluminum castings when using copper-aluminum composite and cast iron chills. Te results appear in the paper, “Effect of Different Chill Materials on Aluminum Casting Solidification and Mechanical Properties” by Steve Robison, American Foundry Society, Schaumburg, Ill.; Stephen Gonczy, Gateway Materials Technology, Mount Prospect, Ill.; Kai Hartman, Denison Industries, Denison, Texas; and Robin Foley, University of Alabama, Birmingham, Ala.


Question What effect does chill material have


on the solidification profile and mechan- ical properties of an aluminum casting?


that copper chills are preferable in areas of a casting that require high heat extraction. In this case study, the research team tested two different chill materials to determine if a copper- based chill would produce preferable mechanical properties and microstruc- ture. Researchers believed the results from this aluminum case study might be applicable to other cast metals. Tis study was part of a larger


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program to establish statistically vali- dated allowable mechanical properties for aluminum alloy E357-T6 sand castings for inclusion in the Metallic Materials Properties Development and Standardization (MMPDS) hand- book, an industry recognized source for aerospace component design allow- ables. Te AFS Cast E-357 Alumi- num Statistical Properties program was accomplished by a consortium of casting users, aerospace casting facili- ties, suppliers and industry support organizations. Tis group assisted in the design of the test casting, gating, chill and riser practice, melt treatment, pouring guidelines, heat treatment parameters and evaluation. Tree different plate castings were


developed, each with two section thicknesses. • Casting 1: 0.187 x 0.5 in. (4.75 x 12.7 mm)


• Casting 2: 1 x 2 in. (25.4 x 50.8 mm) • Casting 3: 1.5 x 2.5 in. (38.1 x 63.5 mm) Project participants were concerned the composite chill package could


November 2013 MODERN CASTING | 45


Background Due to copper’s ther-


mal conductivity, it has been accepted among many aluminum casting engineers


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