Grain Growth And Its Influence On The Mechanical Properties Of Laser-welded 1060 Aluminum Alloy

Under the premise of ensuring good welding seam formation,welding heat input directly affects the working environment adaptability and service life of the welded joint.The weld is often the weakest part of the weld joint.By formulating the correct welding process to enhance the mechanical properties of the weld metal can effectively improve the quality of the workpiece.The growth of grains is closely related to changes in mechanical properties.Therefore,analysis of the weld grain growth under different welding heat inputs and its effect on the mechanical properties can effectively optimize the welding process and improve the performance of the welded joint.So far,many scholars have carried out relevant research on the growth of weld grains,but their research methods are often limited to one of meso-simulation or experiment.In this paper,based on the theory obtained by the predecessors,Take the combination of experiment and numerical simulation,using 1060 aluminum alloy as the test material,the laser welding test and the electron back radiation diffraction(EBSD)observation were carried out.The thermal-elastoplastic method and the combined heat source model are used to perform macro-finite element simulation to analyze the change of the temperature field,heat flow distribution and molten pool shape of the welded joint under different heat inputs.The Monte Carlo(MC)method is used to simulate the grain growth in the weld and compare it with the EBSD test results.Analyze the influence of the change of macro factors caused by different heat input on the size,topology and texture of grain growth.Finally,the mechanical properties of the welded joints are tested to verify the relationship between the grain growth of the 1060 aluminum alloy welds and the mechanical properties of the welded joints.The results show that as the heat input decreases,the temperature field isotherms gradually shrink,and the grain boundary migration energy decreases,resulting in a reduction in the size of the grains.The shape of the molten pool is gradually elongated from elliptical to teardrop.In the process of reducing heat input,dense equiaxed crystals gradually appear in the center of the weld,which inhibits the growth of columnar crystals.The shape of the columnar crystal changes from curved to straight,and the growth direction is consistent with the heat flow vector,which is perpendicular to the front of the solidification boundary,and the angle between the heat flow vector and the center line of the weld is increasing.EBSD results show that when the heat input is reduced to 75 J / mm and 58 J / mm,strong cubic texture appears in the weld area.The generation of cubic texture helps to improve the plastic toughness of the welded joint,at the same time,most of the columnar crystals grow along the <100> direction with obvious preferred orientation;The tensile test results show that as the heat input decreases,the tensile strength and elongation of the joint first gradually increase,and reachthe peak when the heat input is 75 J / mm,and then fall back when the heat input decreases to58 J / mm.Reducing the heat input will lead to the reduction of the grain size and increased grain boundary strengthening results in increased plastic toughness of welded joints;The columnar crystal itself has anisotropy,and its growth direction and tensile force gradually parallel,so as the heat input decreases the tensile strength first produces a tendency to increase;the existence of cubic texture in the weld area It also helps to improve its mechanical properties.However,when the welding speed is too fast,pore defects will occur,which also affects the performance of the welded joint and reduces its tensile strength.