Research On Processes And Properties Of AlSi10Mg Alloy Fabricated By Laser Additive Manufacturing

Compared with titanium alloy,nickel alloy and ferroalloy powder materials,aluminum alloy is prone to pore,deformation and cracking in the process of laser additive manufacturing due to its easy oxidation,high reflectivity,low fluidity and low density.In this paper,the core problems existing in the process of laser processing of aluminium alloys has been studied.The relationship between the size of molten pool and cross-section morphology of single track of AlSi10Mg alloy was determined by laser power(P),and scanning speed(V).The relationship between scanning mode,hatch spacing(d)and the forming quality of the alloy was studied,and the well-formed AlSi10Mg alloy was deposited.In addition,Ti C/AlSi10Mg alloy was prepared with the reinforcement Ti C particles adding in.The distribution of Ti C particles and the effects of Ti C on the microstructure and properties of the alloy were analyzed.Moreover,the problems of porosity,warmth and poor fusion of alloy powder in molten pool were effectively solved by the vibration.Finally,the microstructural evolution,micro-hardness distribution and tensile properties of AlSi10Mg alloy under different vibration frequencies were studied.It was observed by metallographic microscope that the laser power and scanning speed have a great influence on the forming quality of AlSi10Mg alloy in the processing of laser additive manufacturing.When the laser power is too low or the scanning speed is too high,more voids will be formed in the alloy,and the balling will occur if the laser power is too high or the scanning speed is too low.The density of the alloy increases first and then decreases with the increase of laser power,scanning speed and scanning distance,respectively.The density of the AlSi10Mg alloy reaches the maximum(95.8%)at the laser power of 3000 W,the scanning speed of 600 mm/min and the scanning distance of 2 mm.Meanwhile,the pore size and quantity of the alloy surface is the lowest.Some defects such as collapse,porosity and deformation in the alloy occur by single direction scanning.The thermal accumulation effect and the defects in the alloy are reduced by reciprocating scanning,which effectively improves the forming quality of the alloy.Scanning electron microscopy(SEM)showed that AlSi10Mg alloy is mainly formed by overlapping several single-pass alloys,and its structure mainly includes cellular crystal(a-Al)and reticular structure(Si).At the junction of layer and layer,it can be divided into three regions according to the morphology and size of the structure:fine grain zone,coarse grain zone and heat-affected zone.Ti C particles precipitate mainly at the grain boundary,strengthening the grain boundary and refining the alloy structure.The micro-hardness(139.1 HV_0.05)and tensile strength(278.76 MPa)of Ti C/AlSi10Mg alloy are higher than those of AlSi10Mg alloy(88.6 HV_0.05,251.35 MPa).The size and number of pore in AlSi10Mg alloy decrease obviously assisted by high frequency micro-vibration.The structure of the alloy are refined and compact by the effect of vibration.The micro-hardness,tensile strength and tensile strain of the alloy were significantly improved by high frequency micro-vibration.With the increase of vibration frequency,the density,micro-hardness,tensile strength and tensile strain of the alloy first increase and then decrease.When the vibration frequency is 969 Hz,the alloy has the best quality and performance,with density of 99.1%,micro-hardness of 101.2 HV_0.05,tensile strength of 289.28 MPa and tensile strain of 19.3%.