STRENGTH ENHANCEMENT IN THIN-LAYERED AL-CU LAMINATES

Multilayered Al-Cu laminates were prepared by vapor deposition in vacuum onto NaCl substrates. The 25 °C stress-strain characteristics were measured for laminates having total thicknesses of 1.0 and 2.0 μm and layer thicknesses ranging from 20 to 1000 nm. For layer thicknesses ≲70 nm, the yield stress of the laminates is 4.2 times larger and the tensile fracture stress is 2.4-3.4 times larger than the values given by the rule of mixtures for Al and Cu. These strength increases are related to the basic physical properties of the metals and are in good agreement with Koehler's theoretical predictions.