Effect Of High Magnetic Field On The Mechanical Properties And Microstructure Of 2024 Aluminum Alloy And Mechanism Analysis

As one of hard aluminum alloy,2024 aluminum alloy is widely used in the field of aerospace owing to its high strength,small density and excellent heat resistance,however,its further application is limited by poor plasticity.In order to improve the comprehensive performance of aluminum alloy effectively,in this work,the research on the effects of static treatment of magnetic fields and stretching treatment with magnetic fields on 2024 aluminum alloy was carried out based on"magnetoplasticity effect".The microstructure and propreties were researched through advanced modern techniques,such as XRD,TEM,EBSD,Neutron diffraction and so on,to analyse the effect of magnetic field on the plastic deformation of alloy.The research results have been summarized as the following aspects:(1)As for the static treatment of high magnetic fields,the results shows that the optimal comprehensive performance are obtained at B=1T,N=30.Compared with blank sample(σ_b=422MPa,δ=13.8%,σ_v=-24.93MPa),theσ_b,δ,σ_v are 427MPa,16.9%and-1.87MPa,theσ_b andδhave been increased by 1.2%and 22.5%respectively,however,theσ_v has been decreased by 92.7%and better distributed in the presence of magnetic fields.Besides,the microhardness distribution has been improved.As for the microstructure,when B=1T,magnetic fields promote the depinning of dislocations,and then maximized the density of mobile dislocations,which has been increased by24.3%in comparison to the untreated sample.Besides,the average grain size is 40%lower than the original sample,and the maximum refinement is obtained at 1T.After the magnetic field treatment,the weakening of the texture of plane(111)and(220)promotes the crystal slip.(2)As for the stretching treatment with high magnetic fields,the results shows that the tensile strength and elongation of the material are first increased and then decreased with the increasing B,and the optimal mechanical properties are obtained at B=1T,N=30.Theσ_b andδare 441MPa and 16.8%,which have been increased by 4.5%and 21.7%respectively;and the average residual stressσ_v has been decreased by 75.2%from 26.4MPa to 6.5MPa.Besides,the microhardness is also improved with the change of residual stress.As for the microstructure,at B=1T,the dislocation density reached the maximum,73%more than the blank stretch sample.With the further enhancement of B,the dislocations begin to accumulate,leading to the deterioration of the material performance.In addition,in the process of stretching,the magnetic fields promote the refinement of grains,induce the generation of recrystallized grains,and weaken the texture of plane(111)and(200),which improves the grain orientation.(3)When compared with the results of“static treatment of magnetic fields”and“strectching treatment with magnetic fields”,the common characteristics are shown as:at B=1T,N=30,the optimal mechanical properties of the samples are obtained,dislocations are maximized and distribute uniformly.The residual stress and microhardness have been improved during magnetic treatment,at this time,the parameters are believed to optimize magnetoplasticity effect in 2024 aluminum alloy.The main difference lies in that dislocation multiplication is caused by the magnetoplasticity effect during static treatment of magnetic fields.In the absence of external force,there is not enough energy for dislocations to have a long range migration,so lead to the area of dislocation tangles is not wide;besides,the residual stress distribution is uniform by magnetic field treatment.However,in the stretching treatment with magnetic fields,the multiplication of dislocation is the result of the combination of magnetic field and tensile stress.Because the tensile stress provides extra energy for dislocations,the dislocation density is slightly higher than that of static treatment,and the migration is a little longer as well,therefore the area of the dislocation tangles is wider.Nevertheless,due to the existence of tensile stress,the effect of magnetic fields on residual stress is uneven,and the distribution of stress is worse than that of static treatment.