In-situ investigation on the deformation mechanism of duplex microstructure of a near α titanium alloy

•The equiaxed α particles and colonies have discrepancies in hardness, movement slip systems and dislocation level.•The deformation of the duplex microstructure is accommodated largely by the equiaxed α particle.•The colony microstructure is more anisotropic than that of equiaxed α particles.•Dislocation networks and dislocation tangle prevailed in the equiaxed α particle.