Microstructure Evolution and Rheological Behavior of Cooling Slope Processed Al-Si-Cu-Fe Alloy Slurry
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AL-Si alloys offer a number of benefits such as excellent castability, high specific strength, low thermal expansion coefficient, and good corrosion resistance, thus making them suitable for automotive applications. Moreover, these alloys reduce vehicle weight and improve fuel economy in return.[1–3] However, in case of components subjected to high mechanical and thermal cyclic stresses prevailing during service, Al-Si binary alloys become unreliable mainly because of the presence of solidification defects[4] in the cast parts such as macro and micro pores, which become preferential sites for crack nucleation. Al-Si-Cu alloys have shown potential for usage in safety-critical applications pertaining to automobile and aviation industries. In these alloys, copper increases the mechanical strength of the cast parts by precipitating Cu-based intermetallic compounds, both at room and elevated temperatures.[5,6] On the other hand, addition of Fe as an alloying element to these alloys improves their castability and generates thermally stable Fe-based intermetallics. In view of the above, Al-Si-Cu-Fe (A380) alloy has emerged as potentially useful for aerospace and automobile appliances PROSENJIT DAS, Scientist, is with the NNMT Group, CSIRCentral Mechanical Engg. Research Institute, Durgapur 713209, India, and also with the Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India. SUDIP K. SAMANTA, Scientist, is with the NNMT Group, CSIR-Central Mechanical Engg. Research Institute. SUPRIYA BERA, Assistant Professor, is with the Department of Metallurgical and Materials Engineering, National Institute of Technology, Durgapur 713209, India. PRADIP DUTTA, Professor, is with the Department of Mechanical Engineering, Indian Institute of Science. Contact e-mail: [email protected] Manuscript submitted April 2, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
where a combination of mechanical and thermal properties is desirable. Moreover, it combines the benefits associated with the binary Al-Si and Al-Cu alloys, where Si increases strength, fluidity and Cu provides higher ductility compared to binary Al-Si alloys.[7,8] In order to further avoid casting defects associated with the conventional casting techniques, semi-solid casting has emerged as a potential manufacturing technique for automobile and aviation industries.[1–3] The primary goal behind semi-solid processing is to achieve near-spherical grains in the cast parts, by preparing semi-solid slurry having independent islands of spheroidal primary particles. Among the various techniques reported in literature to prepare semi-solid slurry,[9–11] the cooling slope method has gained popularity in recent times owing to its lower costs and ease of operation. Although the cooling slope has been used to generate semi-solid slurry of several types of aluminum alloys,[12–18] very little work has been reported on its application on Si-Cu-Fe (A380) alloy.[7,8] In view of this, the present work has been taken up to investigate the semi-solid processab
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