  Functionally graded materials (FGM) eliminate the stress singularity in the
interface between two different materials and therefore have a wide range of
applications in high temperature environments such as engines, nuclear
reactors, spacecrafts etc. Therefore, it is essential to study the mechanical
properties of different FGM materials. This paper aims at establishing a method
for modelling FGMs in molecular dynamics (MD) to get a better insight of their
mechanical properties. In this study, the mechanical characteristics of Cu-Ni
FGM nanowires (NW) under uniaxial loading have been investigated using the
proposed method through MD simulations. In order to describe the inter-atomic
forces and hence predict the properties properly, EAM (Embedded atom model)
potential has been used. The nanowire is composed of an alloying constituent in
the core and the other constituent graded functionally along the outward radial
direction. Simple Linear and Exponential functions have been considered as the
functions which defines the grading pattern. The alloying percentage on the
surface has been varied from 0% to 50% for both Cu-cored and Ni-cored
nanowires. All the simulations have been carried out at 300 K. The L/D ratios
are 10.56 and 10.67 for Cu-cored and Ni-cored NWs, respectively. This study
suggests that Ultimate Tensile Stress and Young's modulus increase with
increasing surface Ni percentage in Cu-cored NWs. However, in Ni-cored NWs
these values decrease with the increase of surface Cu percentage. Also, for the
same surface percentage of Ni in Cu-cored NW, the values are higher in linearly
graded FGMs than that in exponentially graded FGMs. While in Ni-cored NWs,
exponentially graded FGM shows higher values of UTS and E than those in
linearly graded FGM. Thus, grading functions and surface percentages can be
used as parameters for modulating the mechanical properties of FGM nanowires.
