This study employs 3D molecular dynamics simulations to investigate deformation-induced martensitic transformation (DIMT) in both chemically homogeneous and heterogeneous austenite grains, with particular emphasis on the distinctive role of chemical boundaries. Our findings reveal three fundamental differences between chemical boundaries and conventional interfaces: (i) they do not serve as nucleation sites for martensite formation, (ii) they effectively arrest propagating martensite, yet (iii) they exhibit negligible influence on stacking fault transmission. In the Fe-Ni model system, we demonstrate that DIMT behavior in compositionally graded core-shell austenite grains is predominantly governed by local Ni concentration, where increased Ni content significantly enhances phase stability. These insights demonstrate that precisely engineered chemical heterogeneities offer an effective pathway for controlling DIMT behavior, providing a novel paradigm for designing next-generation steels containing retained austenite with tunable mechanical properties.