| Cold spraying is an advanced coating preparation technology that has received a lot of attention since its inception.In recent years,with the deepening of research,with the advantages of no oxidation and no phase change in the preparation process,cold spraying technology has expanded from preliminary coating preparation to the field of additive manufacturing,and is widely used in the preparation of protection,thermal conductivity,conductive coatings and the repair and remanufacturing of aerospace equipment.In the cold spraying process,the deposition of particles mainly depends on the violent plastic deformation generated by high-speed collision,and accumulates layer by layer to produce deposits.Since it does not rely on external heat input,problems such as oxidation of materials can be effectively avoided.Al and its alloys have high specific strength,good protective properties,and are widely used in aerospace,marine equipment and other fields.However,Al and its alloys are prone to oxidation at high temperatures,and conventional thermal spraying or heat-input additive manufacturing methods are not suitable for the preparation of Al-based materials.Therefore,cold spraying technology has a wide application prospect in the preparation of Al-based materials.In this paper,Al-based protective coatings were prepared by cold spraying technology,and the influence of different process parameters on the performance of Al-based coatings was studied.At the same time,the effects of annealing,hot compression and solution aging treatment on the mechanical properties and microstructure of sediments were explored by cold spraying additive manufacturing of 7050 aluminum alloy blocks.The main research contents are as follows:(1)Study on the influence of process parameters on the preparation and performance of cold spray Al-Zn coating.Al-Zn coating was prepared by cold spraying system,and the influence of process parameter changes on the microstructure and properties of the coating was studied.The experimental results show that the coating compactness is high,but the coating performance is different due to the inconsistent velocity of particles under different process parameters and the degree of plastic deformation of particles.According to the microhardness of the coating and the corrosion resistance of the coating,the process parameters are optimized,and the performance of the coating is relatively best when the spraying temperature is 500℃,the spraying distance is 27mm,and the speed of the powder feeding motor is 1.5r/min.(2)Study on the effect of annealing post-treatment on microstructure and properties of cold sprayed 7050 aluminum alloy block.The properties and microstructure of cold spray 7050 blocks before and after annealing treatment were characterized,and the effects of annealing temperature and annealing duration on the microstructure and properties of the materials were studied.The results show that annealing can effectively improve the mechanical properties of materials by healing particle boundaries and promoting tissue homogenization.According to the material properties after annealing,the combination of the optimized annealing temperature and holding time is 470℃/3h.(3)Effect of hot compression and solution aging treatment on microstructure and properties of annealed cold sprayed 7050 aluminum alloy block.On the basis of optimizing the annealing parameters,the effects of different compression and aging time on the microstructure and mechanical properties of the materials were studied.The results show that after hot compression,the density of the block is obviously improved,and the internal bonding is closer,and the dynamic recrystallization phenomenon promotes the internal microstructure of the material to be further homogenized.On the one hand,solid solution aging treatment promoted the precipitation of a large number of fine precipitated phases,on the other hand,weakened the work hardening phenomenon,and further improved the mechanical properties of the sedimentary body. |
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