Structural deformation and transformation of θ′-Al2Cu precipitate in Al matrix via interfacial diffusion

•Deformation and transformation of θ′-Al2 Cu precipitate in Al matrix is studied.•Directional dependence of diffusion properties is reported.•Mechanism of possible phase transformation from θ′-Al2 Cu to θ -Al2 Cu is unraveled.•Metallurgical technique is proposed to maintain the precipitate stability.