Evolution of Bimodal Microstructure and High-Temperature Wear Resistance of Al-Cu-Ni Alloys
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INTRODUCTION A superior material index (strength/density ratio) at room and elevated temperatures are essential for structural materials in the aerospace and automotive industry. In comparison to steels, aluminum (Al) alloys are
SHUBHADEEP MAITY, BIJAY KUMAR SHOW, and SUPRIYA BERA are with the Department of Metallurgical and Materials Engineering, National Institute of Technology, Durgapur 713209, India. Contact e-mail: [email protected] DIPAK KR. CHANDA is with the School of Materials Science and Nano Technology, Jadavpur University, Kolkata 700032, India. PARTHIBAN RAMASAMY is with the Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, 8700 Leoben, Austria. JU¨RGEN ECKERT is with the Erich Schmid Institute of Materials Science, Austrian Academy of Sciences and also with the Department of Materials Science, Montanuniversita¨t Leoben, Jahnstraße 12, 8700 Leoben, Austria. Manuscript submitted May 3, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
superior in density (four times lower than steels) but have lower yield strength (three times lower than steels).[1–3] Hence, a lot of work has been carried out to improve the strength of Al alloys at elevated temperatures (< 400 C).[4–6] Several Al-based hightemperature phases like ordered phases (NiAl, Al3Ni2, and AlNi3) and in situ grown metal-intermetallic composites (e.g., eutectic Al-Al2Cu, Al-Al3Ni, Al-Al3Sc, Al3Zr, and Al-Al3Fe phases) play a crucial role to accomplish the requirements.[3,7–10] It is well known that application of Al-based high-temperature materials is restricted due to inadequate room-temperature ductility.[11,12] Recent studies have proven that a high-volume fraction of ordered phases, intermetallics, or eutectics with nano-/ultrafine length-scale combined with soft primary dendrites enhances the strength while maintaining moderate ductility due to enhanced dislocation activity.[3,8,13,14] Furthermore, the addition of ternary alloying elements can improve ductility.[3,8] Such ternary additions either yield a combination of two types of eutectics with different length-scale or refine the eutectics and form colonies. Several types of alloys, for example, Al-Cu-Ni, Al-Ni-Cr, Al-Cu-Ag, Al-Ni-Fe, and Al-Ni-Zr,[3,8,15–18] have been developed based on the above considerations. Mainly, Al-Cu-Ni alloys are attractive due to the formation of high-temperature ordered phases and intermetallics (e.g., NiAl, Al3Ni2, AlNi3, and Al7Cu4Ni) and in situ grown metal-intermetallic eutectics (Al-Al2Cu, Al-Al3Ni).[3,7,8,10,18] However, limited data are available on the mechanical property analysis of Al-Cu-Ni alloys.[3,25] Furthermore, vacancy ordered phases (VOPs) is formed in Al-Cu-Ni systems which have a high potential for high-temperature applications due to their high melting point and a high degree of ordering.[19] So far, studies are restricted to fundamental phase analysis of VOPs in Al-Cu-Ni alloys[19–24] due to their monolithic structure. However, it is also interesting to engineer structures to utilize VOPs f
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