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The β→α transformation is a crucial and fundamental phase transformation in titanium and its alloys. This work investigated the effect of elastic compressive stress (ECS) on the microstructure and mechanical property during cooling from β phase region to α + β phase region in Ti-6Al-4V alloy. Results indicated that ECS in this process results in significant refinement and increased aspect ratios of α lamellae (α L) and α colonies (α C). These changes are attributed to the enhanced phase transformation driving force to promote nucleation of α lamellae. The ECS-cooling induced alloy exhibits higher hardness than the stress-free counterpart, mainly resulting from the refined microstructure. This work provides a potential method to tailor the microstructure and improve the mechanical properties of Ti alloys. [Display omitted] • The phenomena of α L refinement are for the first time identified under elastic stress, and the formation mechanism of such phenomena was elucidated. • The elastic compressive stress influences Gibbs free energy are the main reasons for the refinement and variant selection of α lamellae and α colony in Ti-6Al-4V alloys. [ABSTRACT FROM AUTHOR]