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Understanding of stress and its correlation with microstructure near the layer continuous limit in nano‐scaled multilayers
Author(s) -
Majhi A.,
Pradhan P. C.,
Jena S.,
Singh M. N.,
Nayak M.,
Rai S. K.,
Udupa D. V.
Publication year - 2019
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576719001092
Subject(s) - materials science , residual stress , microstructure , composite material , compressive strength , stress (linguistics) , ultimate tensile strength , nanocrystalline material , nanotechnology , philosophy , linguistics
The evolution of residual stress and its correlation with microstructure are investigated systematically in nano‐scaled periodic W/B 4 C multilayers (MLs) as a function of individual layer thicknesses at the ultra‐thin limit (∼0.4–3 nm). Details of the microstructure are accessed through hard X‐ray reflectivity and X‐ray diffuse scattering (rocking scan) measurements. To understand the contributions of stresses in the layers of each type of material to the total stress in ML films, both the total stress in MLs and the stress in nanocrystalline W layers are analyzed and correlated. It is observed that the physical properties of the materials as well as their interfacial morphology undergo significant modification as the layer thickness varies from the continuous to the quasi‐discontinuous regime. A non‐monotonic variation of compressive total residual stress in the MLs is observed as a function of thicknesses of W and B 4 C and explained using a model of the mechanism of film growth. The observed value of in‐plane total compressive residual stress of W/B 4 C MLs is less than the residual stress in W layers in the MLs, which indicates that the net combined stress from B 4 C layers and interfaces is tensile in nature. The observed compressive stress and the increase of lattice spacing with respect to the stress‐free structure in W layers provide evidence of a peening effect. The observed higher surface density of grains with smaller average size and phase formation also provide high compressive stress in W layers.