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Electroless Nickel-Phosphorus Deposits
Published in Fabienne Delaunois, Véronique Vitry, Luiza Bonin, Electroless Nickel Plating, 2019
Suman Kalyan Das, Prasanta Sahoo
Electroless nickel deposits contain internal stresses. These stresses are caused by atomic and crystallographic defects such as dislocations (Taheri 2003). There are numerous theories offered to explain the internal stresses in electroless nickel deposits. The mechanical and corrosion resistance properties of electroless nickel coatings are correlated with the state of the internal stress, which has been studied by many researchers. Although the results obtained are in conflict in some cases, they all agree on the significant effect of internal stress on the mechanical properties of electroless nickel deposits. Internal stresses in electroless nickel plating primarily depend on the coating composition, especially the amount of phosphorus in the deposits. Neutral, compressive stresses are developed when steel is coated more than 10 wt% P (Krishnan et al. 2006). At the same time, phosphorus content below this value produces tensile stresses due to the difference in thermal expansion between the deposits and substrate. The high levels of stresses in these coatings promote cracking and porosity. Structural changes during heat treatment at temperatures above 220°C cause volumetric shrinkage of electroless nickel deposits 4–6 wt%. This volumetric shrinkage increases tensile stresses and reduces compressive stresses.
Improved strength-ductility synergy of directed energy deposited AZ31 magnesium alloy with cryogenic cooling mode
Published in Virtual and Physical Prototyping, 2023
Xinzhi Li, Mugong Zhang, Xuewei Fang, Zhanxin Li, Genghao Jiao, Ke Huang
Since crystallographic information cannot be obtained by optical micrographs, we subsequently analysed the crystallographic orientation and crystallographic defects using EBSD technology, also scanned on the cross-sections (XOZ plane). As presented in Figure 4, the results of grain evolution from EBSD data are consistent with those from optical micrographs. It is worth mentioning that there is almost no twinning in the AC component, while twinning is apparent for the CC component. Those multiple heating and cooling cycling process inherent to WAAM is accompanied by volume expansion and contraction, which in turn accumulates residual stresses within the components (DebRoy et al. 2018). There exists an enforced cooling effect of liquid nitrogen in the CC component, thereby causing greater degree of residual stress. AZ31 Mg-alloys with the low stacking fault energy (SFE) of ∼27.8 mJ/m2 generally relieve residual stress via twinning (Li, Huang, et al. 2022; Zhang et al. 2017).
Influence of tin precursor concentration on physical properties of nebulized spray deposited tin disulfide thin films
Published in Journal of Asian Ceramic Societies, 2018
N. Anitha, M. Anitha, J. Raj Mohamed, S. Valanarasu, L. Amalraj
The dislocation is an irregularity in the crystal structure. It can strongly affect many properties of the materials. Crystalline materials contain a periodic structure with the molecules or atoms placed in repeating fixed positions and this periodicity can be determined by the unit cell parameters. The dislocation or the crystallographic defects interrupt the regular periodic lattice structure. The dislocation density (δ) can be evaluated using relation [27].