Research On Electromagnetic Thermal Intensification Of A356 Aluminum Alloy Components With Hole Defects

Castings inevitably produce hole defects in the casting process.Due to the existence of these defects,when the castings work normally and under the action of external forces,they cause the holes to expand into cracks,which seriously affect the service life of the components,and there are great potential safety hazards.Therefore,this paper combines the previous research experience of electromagnetic heating technology applied to crack arrest and repair,and regards the hole as a generalized oval or circular buried crack.From the aspects of theory,numerical simulation and experiment,the A356 aluminum alloy components with hole defects were studied by electromagnetic heating.Firstly,according to the related theories of fluid mechanics,electrostatics,electrokinetics,heat transfer,and thermodynamics,the distribution functions of the temperature and thermal stress in the aluminum alloy sheet with hole defects were deduced.Taking A356 aluminum alloy as an example,from the theoretical point of view,electromagnetic heating enhancement studies were conducted.The distribution of the temperature field and the thermal stress field in the sample at the instant of pulse discharge was calculated,and the temperature and thermal stress distribution curves were given.Based on the ANSYS finite element software,two-dimensional planar model and three-dimensional solid model of hole-hole A356 aluminum alloy specimen were established respectively,and numerical simulations of electromagnetic heating of the two models were performed.The pulse discharge process was simulated,and the influence of pulse discharge on hole-defective A356 aluminum alloy material was studied.The distribution of temperature field and thermal stress field in the sample was also given.The results suggested that the maximum temperature near the hole could been higher than the melting point of the material when the proper voltage was applied,and the hot and compressive stress was received near the hole defect,which could inhibit crack initiation.Based on the stochastic finite element theory,ANSYS finite element software was used as a platform to analyze the reliability of 2D planar aluminum alloy specimens containing porous holes.The process of sample random sampling statistics was simulated,and the effects of random parameters such as hole radius,discharge voltage and geometric size on the post-discharge results were studied.The correlation coefficients and sensitivity of input and output parameters were analyzed.The pulse discharge of A356 aluminum alloy samples containing self-made holes was performed by ZL-2 super pulse current discharge equipment.Metallographic experiments and tensile properties tests were performed on the samples respectively,and the microstructures around the holes before and after discharge were investigated.The tensile properties of the specimens were compared and analyzed.It was found that the edge of the hole was remelted and recrystallized.Tensile properties experiments showed that the tensile properties of the specimen after discharge were significantly improved.From the aspects of theoretical analysis,numerical simulation and experiment,the study on the discharge strengthening of A356 aluminum alloy specimens containing hole defects showed that the use of electromagnetic heating technology could realize the strengthening of A356 aluminum alloy material containing hole defects.