Achieving isotropic microstructure in an additively manufactured Ti-6Al-4V alloy enabled by dual laser processing

With the development of science and technology and the popularization of intelligent manufacturing, laser additive manufacturing of titanium alloys is being attractive in industrial adoption due to its advantages of nearnet shape and cost-saving features, and especially laser melting deposition is an effective additive manufacturing technique for large-scale and lightweight components such as TC4 alloy. However, inside the as-prepared alloy, large scale columnar crystals are formed along the forming direction, which will lead to anisotropic macroscopic properties of the alloy parts, further affecting their service life. In view of this, we report an innovative strategy of dual laser processing integrating laser melting deposition and laser shock peening, which can be used to achieve isotropic microstructure along three building directions in Ti-6Al-4V alloy. Interestingly, the isotropic microstructure is basket-weave structure of ultrafine & alpha; and nanometer & beta; lamellar colonies together with abundant nanometer & beta; fragments/particles distributed dispersedly inside ultrafine & alpha; matrix. Especially, the as-fabricated alloy exhibits approximately isotropy of mechanical properties along three building directions, and circumvents the strength-ductility trade-off of Ti-6Al-4V alloy with different microstructures reported so far. This study validates the feasibility of manufacturing high performance complex structural components by coupling technology of laser melting deposition and laser shock peening, for grain refinement and isotropic microstructure of additive manufactured titanium alloys in a low-cost and effective method.Impact statement: The proposed dual laser processing technology integrating additive manufacturing of laser melting deposition and synchronous laser shock peening, can provides insight into fabricating isotropic metal components with higher performance through additive manufacturing of one-step forming.