Characterisation of the K-state in Ni-33at.%Cr

The presence of chemical short-range order (SRO) in alloys has long been established and known to influence a range of material properties and phenomena. Whilst historically SRO was identified primarily through changes in the electrical and lattice properties, this can present serious limitations in fully characterising local effects, and with underlying mechanisms not fully understood, local ordering is only implied. However, recent advancements demonstrate Total Scattering as a valuable direct probe for local order in alloy systems. Of specific interest is the ordering of Ni-Cr systems, in which the transformation into a long-range ordered Pt2Mo superlattice has drawn much attention due their use in lifecycle critical components in aerospace or thermocouple applications. As such, understanding the evolution of local order in these systems is critical to current alloy research and the development of novel materials. Previous X-ray studies have been unable to fully capture the extent of ordering in Ni-Cr system due to similar X-ray form factors. However, preliminary work using neutrons has identified the formation of superlattice after as little as 100hrs ageing, implying the occurrence of short-range affects across shorter time scales. To fully investigate this, we propose the assessment of Ni-33at.%Cr treated ex-situ at a series of ageing times to capture the local order evolution through the random to short-range to long-range transformation.