Fundamental knowledge about the microstructural phenomenoma during the production chain is required to be able to render the desired material properties. Apart from experimental studies, numerical methods have shown their capability to predict characteristic material properties. Hence, a phase-field model incorporating free energies from CALPHAD database is employed to analyse curvature-driven shape-instabilities, in the absence of any phase transformations, leading to morphological evolution. This study is meant to extend previous works [Kubendran et. al 2018a, Kubendran et al. 2018b] to capture the influence of the neighbouring rods on the volume-diffusion governed transformation of finite 3-dimensional rods. Analytical expressions predicting the transformation kinetics of these lamellar structures are obtained from the phase-field simulations. It is observed that the terminal rods strongly influence the transformation mechanism. Besides, it is identified that the neighbouring rods introduce a significant change in the carbon redistribution. The interplay between those two aforementioned effects induces a shift of the critical aspect ratio, above which the spheroidization involves the breaking-up of rods ('ovulation'). In addition, it is shown that the magnitude of this shift relates to the interlamellar spacing.