Tensile properties of a free-standing Cu/Zr nanolaminate (or compositionally-modulated thin film)

• Published in: Scripta materialia Vol. 41; no. 9; pp. 929 - 935
• Main Authors: Nieh, T.G, Barbee, T.W, Wadsworth, J
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 08.10.1999; Elsevier Science
• Subjects: Applied sciences; COMPOSITE MATERIALS; Condensed matter: structure, mechanical and thermal properties; COPPER; COPPER ALLOYS; DEPOSITION; Exact sciences and technology; LAYERS; MATERIALS SCIENCE; Mechanical and acoustical properties; METALLIC GLASSES; Metals. Metallurgy; Physical properties of thin films, nonelectronic; Physics; STRAIN RATE; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); TENSILE PROPERTIES; ZIRCONIUM ALLOYS; Thin films; Zirconium; Mechanical properties; Copper; Experimental study; Microstructure; Stress-strain relations; Laminates; Nanostructured materials; TEM; Tensile properties
• ISSN: 1359-6462; 1872-8456
• DOI: 10.1016/S1359-6462(99)00240-7

A novel, free standing nanocrystalline Cu/amorphous Cu sub 4 Zr sub 3 laminate has been produced by a sputter deposition method. The material possesses a very high yield and tensile strength while still retaining a reasonable tensile elongation (approx4%). For example, the yield and tensile strengths of the nanolaminate at a strain rate of 2x10 exp -3 s exp -1 are 600 and 1120 MPa, respectively. These values are significantly higher than the yield and tensile strengths of nanocrystalline Cu, which are only 180 and 275 MPa, respectively. The high strength properties of the nanolaminate are attributed to the fact that the amorphous layers are constrained by interfacial bonding to deform in conformity with the Cu layers. Therefore, the neck instability that normally occurs in an amorphous material during tension is suppressed; the amorphous layers can be elasticially stretched to an appreciable degree of strain without fracturing. This allows the full utilization of the high strength property of the amorphous phase. In addition to the high strength properties, Cu-Zr nanolaminates show a strong work hardening characteristic (Napprox0.55) and significant strain rate dependence (mapprox0.044). The exact description of the stress-strain behavior of the nanolaminate needs a theory that is beyond the isostrain model.