Formation Mechanisms and Microstructure Characterization of Al/Al 3 Ni In-situ Composite by Compound Casting
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INTRODUCTION
AL/Ni bimetal composites are suitable for practical applications which need high strength, fatigue, creep resistance, and good ductility and toughness.[1–3] The method by which the composite is produced directly affects the size, shape, and distribution of the intermetallic reinforcing particles. Various researches have been made to fabricate Al–Al3Ni composites. These methods include low-pressure infiltration,[4,5] friction stir processing,[6] mechanical alloying,[7] and accumulative roll-bonding.[8] These methods are expensive due to high energy consumption and/or higher price of equipment compared to compound casting. Compound casting is mainly used for joining two dissimilar metals to each other. In this method, two metallic materials, one in the solid state and the other in the liquid state, are brought into contact with each other. An intermediate intermetallic layer at the interface of the two metals is formed, which provides the bonding between the metals. This method, however, can be used as a cost-effective process for the production of complex structures. By knowing the formation
M. SISTANINIA, H. DOOSTMOHAMMADI, and R. RAISZADEH are with the Department of Metallurgy and Materials Science, School of Engineering, Shahid Bahonar University of Kerman, Jomhoori Eslami Blvd., Kerman, Iran. Contact e-mail: [email protected] Manuscript submitted April 29, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
mechanisms of intermetallics at the interface and their distribution in a metallic matrix, a method to produce in-situ composites can be developed. In recent years, different metal pair systems, such as Al/Mg,[9] steel/aluminum,[10] Al/Al,[11] and Al/Ti,[12] have been subjected to investigations. The bonding between Al and Ni couples by compound casting method has not been studied so far. This paper focuses on the in-situ fabrication of Al/Ni composite by the compound casting process. This method is based on the interaction of liquid Al and solid Ni followed by the formation and distribution of intermetallic particles within the Al matrix.
II.
EXPERIMENTAL PROCEDURE
Commercially pure Al (99.71 wt pct) and commercially pure Ni (99.99 wt pct) were used as the initial casting materials. A cubic core with the dimensions of 15 9 10 9 85 mm was machined from a Ni ingot. Its surfaces were then ground with silicon carbide papers up to 1200 grid, rinsed with acetone and placed within a cylindrical cavity of a silica sand mold with 90 mm diameter and 65 mm height. An open feeding system was used for avoidance of shrinkage voids. Initially, Ni solid core was inserted vertically in the sand in the bottom of mold. Thereafter, Al ingot was melted in an electric resistance furnace. The molten Al with a temperature of 973 K, 1073 K or 1173 K (700 °C, 800 °C, or 900 °C) was poured into the gating system where Al passed the gating system and filled the mold
completely under normal atmospheric condition. Figure 1 shows the schematic sketch and the dimensions of the mold used in this research. To study the interfacial mic
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