A Study on the Formation of Intermetallics During the Heat Treatment of Explosively Welded Al-Ti Multilayers
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MATERIALS like intermetallic compounds that are solid at high temperatures and have high values of strength-to-weight and stiffness-to-weight ratios are in demand for high-temperature structural, aircraft, and aerospace applications.[1] Intermetallics such as Ti3Al and Ni3Al maintain their strength and even develop reasonable ductility at elevated temperatures. Low ductility at room temperature, though, has impeded further development of these materials.[2] Titanium aluminide intermetallic compounds offer an attractive combination of low density and good oxidation and ignition resistance with unique mechanical properties. Thus, these compounds belong to the few classes of emerging materials that have the potential to be used in demanding high-temperature structural applications
FARZAD FOADIAN, Research Assistant, is with the Institute of Metallurgy, Clausthal University of Technology, 38687 ClausthalZellerfeld, Germany. MANSOUR SOLTANEIH, Professor, and MANDANA ADELI, Assistant Professor, are with the Center of Excellence for High Strength alloys Technology (CEHSAT), School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Narmak, 1684613114 Tehran, Iran. Contact e-mail: [email protected] MAJID ETMINANBAKHSH, Technical Manager, is with the Hezar Azar Company, Shahab Bldg., ValiAsr Street, 1511735115 Tehran, Iran. Manuscript submitted August 7, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS A
whenever specific strength and stiffness are of major concern.[3] The five main intermetallics in the Ti-Al phase diagram are Ti3Al, TiAl, Ti2Al5, TiAl2, and TiAl3.[4] There are many methods for producing intermetallics and intermetallic composites; the final properties of the product dictate the production methods.[4] Various melting processes like vacuum arc melting,[5] plasma arc melting,[6] induction skull melting,[7] casting processes,[8] rapid solidification,[9] thermal spraying,[10] solid state processes,[11–15] powder metallurgy,[16–18] and thin layer synthesis[19,20] have been applied as the production routes for these group of materials. Among the titanium trialuminide-based composites, the multilayer ‘‘metallic–intermetallic laminate’’ (MIL) composites should be emphasized, which possess a unique set of mechanical properties. An important advantage of the multilayer composites is the possibility of combining the properties of both the hard and refractory intermetallics and the ductile matrix.[21] Explosive welding is an interesting bonding process for producing bimetallic and multilayer compounds with high mechanical properties, which offers an excellent alternative for joining dissimilar metals and alloys with varying physical and metallurgical properties. The high strength and fracture toughness of explosively welded materials are due to the particular structural state of the welds formed by the dynamic interaction of the work pieces.[22] It is a solid state metal-joining process that produces a weld joint by high velocity oblique impact, aided by controlled detonation with
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