Microstructural Evolution and Mechanical Properties of Nanointermetallic Phase Dispersed Al 65 Cu 20 Ti 15 Amorphous Mat
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DEVELOPMENT of lightweight structural materials with high specific strength is always of great importance for technological advances in the transportation and aviation industry. Mosumoto[1] predicted that the strength of aluminum alloys could be significantly enhanced from about 600 MPa in the age-hardened condition to over 1500 MPa in the rapidly quenched amorphous alloy or nanocrystal dispersed amorphous matrix composite. Hence, considerable success was achieved in the recent past in synthesizing Al-based engineering alloys in amorphous state or nanointermetallic phase dispersed amorphous matrix condition either by mechanical alloying or rapid solidification.[2–10] D. ROY, Assistant Professor, is with the Materials and Metallurgical Engineering Department, National Institute of Foundry and Forge Technology, Ranchi 834003, India. R. MITRA, Professor, is with the Metallurgical and Materials Engineering Department, Indian Institute of Technology, Kharagpur 721302, India. O.A. OJO, Professor, is with the Mechanical and Manufacture Engineering Department, University of Manitoba, Winnipeg, MB R3T 2N2, Canada. W. LOJKOWSKI, Professor, is with the Polish Academy of Sciences, Institute of High Pressure Physics (UNIPRESS), Sokolowska 29/37, Warszawa 01-142, Poland. I. MANNA, Director, is with Central Glass & Ceramic Research Institute, Jadavpur, Kolkata 700032, India. Contact e-mail: [email protected] Manuscript submitted October 11, 2009. Article published online April 2, 2011 2498—VOLUME 42A, AUGUST 2011
However, these novel materials are available only in the form of ribbon, wire, film, or powder, and are therefore difficult to consolidate into bulk components of large dimensions. Among different possibilities, hot/ warm pressing or extrusion is a possible method to fabricate the bulk sample from mechanically alloyed powders. During pressing at high pressure and temperature, there could be partial crystallization of the amorphous phase or grain coarsening of the nanocrystalline aggregate.[8,11] It is known that mechanical properties of nanocrystalline materials are highly sensitive to the presence of internal defects, heterogeneities, and grain size distributions[12–14] caused during the consolidation of the nanocrystalline powders. Hence, the consolidation process needs to be optimized for the production of dense nanocrystalline materials with reasonably narrow grain size distributions. In recent years, the hot isostatic pressure was successfully used to obtain dense and near-net-shape bulk products from nanometer-size powders.[15,16] Hot isostatic pressing (HIP) involves simultaneous application of high pressure (usually through an inert gas) at an elevated temperature in a specially constructed vessel.[17] The pressure is applied isostatically using a gas in order to fabricate near-net-shape components. Under suitable conditions of heat and pressure, internal pores or defects within a solid body collapse and weld up.[18] The HIP process needs a much shorter time for complete METALLURGICAL AND MATERIALS TRANSACTIONS A
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