Research On The Microstructure Control And Mechanical Properties Of AlN Nanoparticles Reinforced Aluminum Matrix Composites

With the continuous improvement of lightweight and energy saving and emission reduction standards,high-quality development of transportation,aerospace and military industries urgently needs high-performance light alloy materials.Compared with traditional ferrous metals,aluminum composite materials(AMCs)have many performance advantages,such as low density,high specific strength,good electrical conductivity and creep resistance,etc.Therefore,it has received widespread attention.However,after long-term research on aluminum composite materials,it has been found that the performance improvement of aluminum composite materials with uniform structure seems to have reached the bottleneck stage.Therefore,the research focus of many scientific researchers has turned to aluminumbased composite materials with non-uniform structure,and more and more non-homogeneous aluminum-based composite materials have been designed and developed,and their performance has been greatly improved.A long-term study has shown that with the introduction of the reinforcing phase,the room temperature strong plasticity matching contradiction of the material will become larger,which is usually manifested as an increase in strength and a decrease in plasticity.At the same time,with the increase in the amount of reinforcement phase,the improvement of the material strength is relatively limited,but the plasticity will drop sharply,or even no plasticity,and a better strong plastic match can be obtained by adjusting the structure of the material.In view of the above problems,this article takes the AlN/Al composite prepared by in-situ synthesis method as the research object,and adopts material processing methods such as hot extrusion,rotary swaging deformation,heat treatment,adding alloying elements,high pressure torsion,etc.to control and design a variety of different AlN/Al composites structure.Through the design and control of the structure,the influence of the non-uniform structure on the mechanical properties of the AlN/Al composite is analyzed,and the effect of alloying on the improvement of the mechanical properties of the material at room temperature is further explored.Metallographic microscope,scanning electron microscope,electron backscatter diffraction technology and transmission electron microscopy and other material analysis and characterization methods are carried out in-depth research and discussion.The main conclusions are as follows:(1)Structure regulation and strengthening mechanism of AlN/Al nanocompositeThe two-stage heterogeneous AlN/Al composites with both AlN granular network structure and coarse-grained pure Al lamellar structure have excellent room-temperature strong plasticity.The coarse-grained pure Al lamellar structure can improve the work hardening ability and provide a small amount of HDI(heterogeneous deformation induced)stress,while the AlN granular network structure can provide a large HDI stress.(2)Microstructure and mechanical properties of AlN/Al-Mg compositeThe addition of Mg element contributes to the grain refinement of Al matrix,and the solution strengthening effect improves the room temperature strength of AlN/Al composites greatly,but the plasticity will lose to a certain extent,and the plasticity will decrease more obviously with the increase of Mg element.(3)Effect of high pressure torsion on the microstructure and room temperature mechanical properties of AlN/Al-Mg compositesAfter high pressure torsion in high density of dislocations,para wrong layer of solid solution strengthening effect and Mg elements and fine grains have significantly increased the strength of the trace Mg elements of dynamic recovery and dynamic recrystallization inhibition is weak,will appear in the process of high pressure reverse dynamic recovery and dynamic recrystallization,thus improve the plastic.