Acquisition of special shape molten pool in laser deep melting of titanium alloy under the action of modulated laser

Abstract Some interesting phenomena were ignored by regular modulation of the output of laser energy in laser deep melting process. In this paper, the morphology of laser deep melting pool was studied under three different processing parameters, continuous laser, 2kHz and 20kHz modulated laser. And high-density modulation laser deep melting process parameters with high aspect ratio (D/W=1.49) were obtained. The modulation laser deep penetration repair of 3mm deep incision was realized, and the longitudinal section of the repaired area was high density and no air hole. By studying the XRD phase analysis, metallographic microstructure and microhardness distribution of the repaired area, the mechanism of dislocation strengthening and grain refinement under the effect of modulated laser high frequency shock was revealed. Comparison of tensile tests of specimens contained with repaired areas showed that, the comprehensive mechanical properties were not lower than the substrate after repair by modulation laser.