Cold spray additive manufacturing (CSAM) uses a high-speed collision of micrometric powder to produce a deposit via an intense and highly localized plastic deformation accompanied by large strain gradients, that strongly governs the microstructural changes in the powder particles upon impact, and thus the mechanical properties of the deposit. Here, an AlSi10Mg deposit is fabricated using high-pressure cold spraying, where AlSi10Mg powder particles are accelerated by helium onto an Al 7075-T6 substrate. To investigate the microstructure-sensitive deformation and the dislocation evolution, a representative volume element (RVE) is built and coupled with a crystal plasticity (CP) constitutive framework that accounts for a dislocation-mediated hardening and predicts spatially resolved statistically stored dislocation (SSD) along with geometrically necessary dislocation (GND) densities. The RVE consists of a Voronoi cellular architecture made of coarse-grained (CG) inside a grain, and grain-boundary-affected zones. This model considers a mixed transition region to capture strain incompatibility and anisotropy arising from the interactions among recrystallized ultrafine grains (UFG), precipitates, and deformed CG domains. Simulations reveal pronounced strain partitioning between the UFG-rich transition zone and the CG domains due to microstructural heterogeneity. Plastic strain localization is driven by the accumulation of incompatible plastic slip across interfaces, leading to elevated GND densities concentrated near the domain boundaries, whereas SSD density increases within highly strained grain zones inside the grains. This CP-RVE framework links strain gradients to dislocation structures and mechanical macroscopic response.