| Aluminum alloys are widely used in aerospace,industrial and social products because of their high specific strength and stiffness,good plasticity and other excellent properties.However,with the development of industry and society,the performance of aluminum alloy can no longer meet the needs of certain occasions.Thus,composites formed by adding reinforcing phases such as ceramics and fibers to aluminum alloys came into being.Aluminum matrix composites are widely studied and used because of their high stiffness,low density,and good wear resistance.In this study,Ni-modified graphene/2024 aluminum matrix composites with graphene content of 0.5wt.%and 1wt.%were prepared by powder metallurgy.Furthermore,the MMS-100 thermal simulation tester was used to conduct hot compression tests on composite materials and 2024 aluminum alloy.The relationship between deformation temperature,strain rate and flow stress during the hot deformation of composite materials was investigated.Establishing the constitutive equations of composite materials based on the Arrhenius constitutive model.Calculate the hot processing maps of the material based on the dynamic material model and determine the optimal processing parameter interval for this experimental parameter.To provide a theoretical basis for developing and optimizing the thermoforming process parameters of Ni-modified graphene/2024 aluminum matrix composites.Rolling of composite materials to verify process parameters based on optimal processing parameters.To observe the microstructure after hot compression and analyze the evolution pattern of the organization at each parameter.Study the effect of Ni-modified graphene content on the properties and organization of composite materials.The main findings of the study are as follows:According to the true stress-strain curves of Ni-modified graphene/2024aluminum matrix composites,an increase in deformation temperature or a decrease in strain rate will lead to a decrease in flow stress.Constitutive equations of Ni-modified graphene/2024 aluminum matrix composites calculated from stress-strain data.And the strain activation energy of 222.22951 k J/mol was derived for the composite with0.5wt.%graphene content.The optimal processing interval for composites with graphene content of 0.5wt.%was determined by analyzing the hot processing maps for a strain rate of 0.011-0.368s-1and a temperature of 420-450°C.By comparing the hot processing maps of 2024aluminum alloy with graphene content of 0.5wt.%and 1wt.%of composites.The incorporation of Ni-modified graphene was found to shift the optimal processing interval of the composite towards the high temperature and medium strain rate regions and reduce the material’s power dissipation rate.The increase of Ni-modified graphene content reduces the optimal processing interval of the composite.The analysis of the hot compression organization revealed that the more intense the occurrence of dynamic recrystallization with increasing deformation temperature or decreasing strain rate of Ni-modified graphene/2024 aluminum matrix composites.Compare the composites of 2024 aluminum alloy with graphene content of 0.5wt.%and 1wt.%.Ni-modified graphene incorporation promotes the occurrence of dynamic recrystallization but limits the growth of dynamically recrystallized grains,thus refining the dynamically recrystallized grains.When the graphene content was increased from 0.5wt.%to 1wt.%,the limitation of Ni-modified graphene on the growth of dynamically recrystallized grains was weakened due to the agglomeration of Ni-modified graphene.Hot-rolled processing experiments and mechanical property tests on composite materials at 450°C and 0.05s-1 strain rate in the optimal processing interval.The tensile strength and elongation of aluminum matrix composites with graphene content of0.5wt.%increased by 4.8%and 43.8%compared to that before rolling.The tensile strength and elongation of the composites with graphene content of 1wt.%increased by 3.6%and 41.7%. |
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