Influence of the microstructure on the mechanical properties of Ni/Sn multilayered composites

Ni/Sn multilayer composites with different layer spacings and Sn volume fractions are prepared by electrodeposition, and their mechanical properties are characterized. It is shown that the mechanical properties of these composites greatly depended on their composition (Sn vol%) and layer thickness. The ultimate tensile strength (UTS), yield strength (YS), and Young's modulus of the composites with variable Sn content increased with decreasing Sn volume fraction. The measured UTS and YS values are generally found to be either equal to or greater than the values predicted by the rule-of-mixtures because of the strengthening effect of the multilayered microstructure. Considerable enhancement in the UTS and YS is observed in composites with smaller layer spacing. This enhancement in strength is attributed to pinning of dislocations at the interfaces of the layered structure. The dependence of the YS on the layer spacing followed the Hall-Fetch relation. The Hall-Fetch constants, a, and ii: in the multilayer composites are theoretically calculated and found to be comparable with the experimentally measured values. (C) 1999 Elsevier Science S.A. All rights reserved.