Strength Enhancement in Thin-Layered Metal-Metal Laminates.

摘要

The concept of obtaining high strength/weight ratios and resistance to brittle fracture from thin-layered metal-A/metal-B laminates, in which metal A has a high dislocation-line energy and metal B has a low dislocation-line energy, was proved. Multilayered Al-Cu laminates were prepared by vapor-deposition in vacuum onto NaCl substrates. The 20C stress-strain characteristics were measured for Al-Cu laminates having total thicknesses of 1.0 and 2.0 micrometers and individual layer thicknesses of 10, 20, 30, 40, 50, 60, 80, 100, 200, 500, and 1000 nm. For layer thicknesses approximately less than or equal to 70 nm, the yield stress of the Al-Cu laminates was 420% larger, and the tensile fracture-stress was 250-320% larger, than the values calculated from the rule of mixtures for Al and Cu. Epitaxial growth of the Al and Cu layers was shown to be feasible for substrate temperatures > 100C, but at these temperatures intra-layer diffusion may affect the sharpness of the interfaces between layers. A series of Al-Ni laminates was prepared, but 200-250C substrate temperatures that were necessary to obtain internal-stress-free Ni layers caused excessive intra-layer diffusion.