Research On The Heat Treatment Process Of 2A12 Aluminum Alloy By Arc Additive Manufacturing

2A12 aluminum alloy has become one of the most widely used metal material in the field of aircraft manufacture with its excellent specific strength and good processability.As an advanced manufacturing technology,arc additive manufacturing,can achieve the rapid prototyping of large complex structural 2A12 aluminum alloy parts.However,due to the high temperature gradient and inhomogeneous temperature field in process of manufacturing,it is prone to generate harmful residual stresses and nonequilibrium microstructure inside the material,accompanied by coarse grains and segregation.Heat treatment can effectively adjust the segregation and mechanical properties of 2A12 aluminum alloy manufactured by arc additive manufacturing.Therefore,research on the heat treatment process for as-deposited 2A12 aluminum alloy is carried out.Meanwhile,friction stir welding technology is introduced as an assistive technology to solve the problems about coarse grains and porosity,and research on the heat treatment process for as-deposited 2A12 aluminum alloy weld by friction stir welding is also carried out.From all of those investigations,the important conclusions are as follows:(1)The forming mechanism of arc additive manufacturing is analyzed,and the microstructure and mechanical property of as-deposited 2A12 aluminum alloy is observed.The top zone of as-deposited 2A12 aluminum alloy mainly consists of fine dendrite grains,and inter layer organization of middle zone mainly consists of coarse columnar grains,while the grains of bottom zone are columnar dendrite grains growing perpendicular to the substrate.There are no definite distribution rules of porosity along the height direction.The tensile strength value of as-deposited 2A12 aluminum alloy is 176 MPa,and the yield strength value is 93 MPa,while the elongation reaches 22.2%;(2)The orthogonal experiment on heat treatment process optimization is carried out.It shows that solution temperature is the parameter whose effect on all of the three indexes of mechanical properties is the most significant among effects of the four parameters,followed by aging temperature.Besides,the maximum tensile strength is 438 MPa in the orthogonal experiment,and the maximum value of the yield strength is 322 MPa,and the maximum elongation value is 25.3% as well.The reasonable heat treatment process parameters are 505??60min?190?and 14 h respectively;(3)The forming mechanism of arc additive manufacturing assisted by friction stir welding technology is analyzed,and preliminary explorations of the heat treatment process is carried out.The results show that coarse grains of the joints are refined,and the porosity is also eliminated partly.However,there is a hole defect throughout the weld bead because of unsuitable manufacture process parameters.Strength value is slightly increased while the ductility is significantly enhanced after the introduction of friction stir welding technology.The tensile strength after optimized heat treatment is 321 MPa,the yield strength is 218 MPa,and elongation is 8.1%,which is comparable to the elongation of forgings of T6.Compared with the enhance effect on mechanical properties of traditional T6 heat treatment,the effect of optimized heat treatment is more significant.