Research On Melting Structure Regulation Of Molten Pool In Arc Powder Additive Manufacture Based On Pulse Laser Oscillation

Additive manufacture of metal components?3D printing?technology is an advanced manufacturing technology that integrates multidisciplinary development of information technology,new material technology and manufacturing technology.However,the application of this technology to product development still faces major challenges.More and more application fields have put forward expectations for the regulation of macro and micro fusion structures of metal components,which require shape control and control of the 3D printing manufacturing process of metal components.In this paper,an experimental system of arc-loaded powder-based additive manufacturing based on pulsed laser oscillation is established.The two methods of PTA and Laser-PTA are studied from the aspects of macroscopic forming morphology,microstructure and mechanical properties.The thermal cycling characteristics and the characteristics of the molten pool oscillations have systematically explored the mechanism of pulsed laser to regulate the melting structure.The main conclusions are as follows:?1?For single-layer fused structures,the addition of a suitable pulsed laser improves the forming quality,improves the metal powder deposition efficiency,and increases the forming coefficient,but has no significant effect on the spread-ability of the molten pool.For multi-layer fusion structures,the pulsed laser enhances the local fluidity of the liquid metal,improves the forming quality,and reduces the tendency of the molten pool to overflow.At the same time,it has a smaller effect on the layer width of the forming,which increases the layer height and improves the powder deposition efficiency.Increasing the forming factor facilitates the forming of thin-walled parts and fine structures.?2?Based on the comparison of samples with and without pulsed laser plasma arc additive manufacturing,it is found that columnar crystals or coarse primary dendrites exist in different regions without lasers,and the crystal grains grow preferentially;after adding an appropriate pulsed laser,the crystals are transformed into equiaxes Crystals or fine dendrites,anisotropy weakens;pulsed laser expands the range of the superheated zone in the interlayer region of the multi-layer fusion structure;weakens the concentration of the precipitate M₂₃C₆ at the grain boundaries;the austenite phase changes from a lath Into a skeletal shape;the microscopic pores at the grain boundaries are significantly reduced,ensuring good compactness.?3?The use of EBSD technology found that the average grain size decreased,the texture strength decreased,the dislocation density decreased after the pulsed laser was added.In particular,the effect of increasing the pulsed laser frequency on the grain size,texture,and dislocation density becomes more significant.The mechanical property experiments found that the pulsed laser enhanced the toughness and tensile strength by fine grain strengthening.?4?Using the thermal cycle temperature curve,it is found that the peak and valley temperatures increase and the cooling rate slows down.The pulsed laser increases the heat input of the arc bath.The high-speed camera was used to analyze the oscillation effect of the molten pool.The addition of pulsed laser caused the obvious oscillation of the arc molten pool.Based on the two solidification mechanisms of grain fragmentation and heterogeneous nucleation,the regulation mechanism of the fusion structure of the molten pool based on the pulsed laser oscillation of the arc powder-loaded additive manufacturing was proposed.