Thermal stability of a nanolayered metal joint

Recently, the first microstructure-preserving approach to metal joining of physical vapor-deposited nanolaminates was introduced. In a subsequent study, this metal lap joint is exposed to annealing cycles with target temperatures of 100°C, 200°C, 400°C and 800°C. The thinning-out ends (wedges) of the laminate and overlapping laminate of the lap joint provide challenges as well as new insights into thermal stability of nanolaminate. Energy dispersive x-ray spectroscopy mapping in the Scanning Transmission Electron Microscope (STEM) of the joint cross section proves that melting of the Cu-layers initiates at the tip of the wedges, where the laminate interface is as susceptible to melting as the lamina interface. A Melting Point Depression curve for the Cu/Nb nanolayered metal joint is established. The article further introduces the protective effect of covering laminate as the Shielding Effect and discusses the counteracting phenomena Melting Point Depression and Shielding Effect.