Tensile Property of Cold-Rolled Foils of Ni-Based and Co-Based L1 2 Intermetallic Alloys
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0980-II05-25
Tensile Property of Cold-Rolled Foils of Ni-Based and Co-Based L12 Intermetallic Alloys Yasuyuki Kaneno1, Takayuki Takasugi1,2, and Tadamichi Myoki1 1 Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 5998531, Japan 2 Osaka Center for Industrial Materials Research, Institute for Materials Research, Tohoku University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 5998531, Japan
ABSTRACT Polycrystalline L12-type Ni3(Si,Ti), Co3Ti and Ni3Al alloys prepared through the thermomechanical process from arc-melted ingots were successfully cold-rolled to thin foils with a thickness of below 200µm. The cold-rolling with over 90% reduction in thickness was possible without providing intermediate annealing. The cold-rolled foils showed high tensile strength (~2GPa) at room temperature due to heavily cold rolling although no plastic elongation was observed. Room temperature tensile elongation increased with increasing annealing temperature, and reached to ~30-40% by high temperature annealing at 1173K. Among three kinds of intermetallic alloys, the Ni3(Si,Ti) foil annealed around at 900K exhibited an extremely high tensile strength and yield strength (over 2GPa) with a reasonable tensile elongation. The observed tensile properties, especially tensile strength at low temperature for the present intermetallic foils were found to be superior to those for the conventional alloys such as nickel based alloys and stainless steels. INTRODUCTION In most of intermetallic compounds and related alloys, plastic deformability especially at low temperature is very poor because slip deformation is difficult due to their complex crystal structures. By contrast, L12 structure derived from A1 (fcc) structure is composed of a relatively simple crystal lattice, and therefore slip deformation is expected to occur even at low temperature. In fact, the Ni3Al, Ni3(Si,Ti) and Co3Ti alloys with L12 structure have fairly good plastic deformability, and thereby fabrication by cold rolling has been applied to these L12 ordered alloys. Hirano et al. have recently fabricated thin foil of boron-free Ni3Al with a thickness of below 100µm by cold rolling using directionally solidified single crystals [1,2]. More recently, it has been reported that a nanocrystalline Ni3Al foil was produced from an ascast coarse-grained sheet by heavy rolling at liquid nitrogen temperature and subsequent recrystallization [3]. However, whether or not other L12 ordered alloys such as the Ni3(Si,Ti) and Co3Ti alloys are fabricable to thin foils has not been yet reported. In this study, we employed conventional polycrsytalline ingots of the Ni3(Si,Ti), Co3Ti and Ni3Al alloys as starting materials. These ingots were thermomechanically treated and then coldrolled to thin foil with a thickness of below 200µm. The purpose of this paper is to present roomand high-temperature tensile properties of the cold-rolled and annealed foils of these L12 ordered alloys.
EXPERIMENTAL The nominal compositions of t
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