Influence of Effective Laser Energy on the Structure and Mechanical Properties of Laser Melting Deposited Ti6Al4V Alloy

Abstract

The laser energy density (ED) is often utilized in many additive manufacturing (AM) processes studies to help researchers to further investigate the process-structure-property correlations of Ti6Al4V alloys. However, the reliability of the ED is still questionable. In this work, a specific empirical calculation equation of the effective laser energy (Ee), which is a dimensionless parameter in laser melting deposition (LMD) processing, was proposed based on the molten pool temperature. The linear regression results and the coefficient of determination prove the feasibility of the Ee equation, which indicates that Ee can more accurately reflect the energy-temperature correlations than the commonly used laser energy density (ED) equation. Additionally, Ti6Al4V components were fabricated by the LMD process with different Ee to investigate the influence of Ee on their structure and mechanical properties. Experimental results show that the detrimental columnar prior β meso-structure can be circumvented and the uniform α + β laths micro-structure can be obtained in LMD Ti6Al4V by a judicious combination of the process parameter (P = 2000 W, V = 12 mm/s, and F = 10.5 g/min) and Ee (7.98 × 105) with excellent tensile strength (1006 ± 25 MPa) and elongation (14.9 ± 0.6%). Overall, the present work provides an empirical calculation equation to obtain a clearer understanding of the influence of different process parameters and indicates the possibility to fabricate the Ti6Al4V alloy with excellent mechanical properties by parameter optimization in the LMD process.