A specialty superalloy is engineered with the following atomic composition and…
CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
A specialty superalloy is engineered with the following atomic composition and corresponding atomic radii.
Element Atomic fraction / % Atomic radius / pm
Ni 90 124
Mo 6 139
B 4 87
In the solid alloy, nickel’s face-centred cubic lattice is preserved.
Use the data to analyse the roles of molybdenum and boron in the alloy.
(a) For each minor element (Mo and B), identify whether its atoms primarily occupy lattice sites or interstitial sites. Classify each as participating in a substitutional mechanism, an interstitial mechanism, or both.
(b) Justify each classification in part (a) by referencing quantitative comparisons of atomic radii and discussing the extent of local lattice distortion expected.
(c) Predict, with reasoning, which of the two minor elements will have the greater effect on the alloy’s yield strength. Your argument should connect atomic-scale structural features to macroscopic mechanical behaviour.
(d) Considering the combined presence of both Mo and B, evaluate how simultaneously operating substitutional and interstitial mechanisms might influence the overall electrical conductivity of the alloy relative to pure Ni. Provide a brief explanation rooted in electron scattering or lattice vibration arguments.