Mechanical Properties And Microstructure Experimental Study On Hot Power Backward Spinning For As-cast 7075 Aluminum Alloy Tube

Due to the characteristics of light weight,high specific strength and corrosion resistance,7075 high-strength aluminum alloy thin-walled tubes are widely used in aerospace,weapons and automotive industries.Using the new casting and spinning process of "casting tube + hot power backward spinning" to manufacture thin-walled tubes has the advantages of high material utilization,high forming accuracy and low cost,which can meet the requirements of aerospace for lightweight,high-performance and green manufacturing and other requirements,and it has become one of the important manufacturing methods for thin-walled tubes.However,the hot power backward spinning process is characterized by local continuous loading,multi-field and multi-parameter coupling,etc.,resulting in the microstructure evolution of the material is complicated during the spinning process.The microstructure of the tube determines its mechanical properties.Thus,this paper takes the as-cast 7075 aluminum alloy spinning tubes as the research object,and studies the influence of process parameters on the mechanical properties and microstructure of the spinning tubes through experiments,and obtains the optimal process parameters.And the effect of subsequent heat treatment on the mechanical properties of spinning tubes was studied,which provides a certain reference for improving the service performance of structural parts such as aerospace and weaponry.The main experimental research contents and results of this paper are as follows:(1)Experiments were carried out on as-cast 7075 aluminum alloy spinning tubes,and the effect of process parameters on the tensile strength,yield strength and elongation after fracture of the tubes was obtained.With the increase of the reduction,the tensile strength and yield strength of the tubes increase,while the elongation after fracture decreases;with the increase of preheating temperature,the tensile strength,yield strength and elongation of tubes increase first and then decrease;with the feed ratio increasing,tensile strength and yield strength of tubes first increase and then decrease,while the elongation after fracture decrease first and then increase slightly;with the increase of friction coefficient,the tensile strength and yield strength of tubes increase first and then decrease,but the overall change is not obvious,and the elongation after fracture increase firstly and then tended to be stable.(2)Based on the multi-objective process parameter optimization design based on the orthogonal test and grey correlation degree,the sequence of process parameters that have a significant impact on the mechanical properties of as-cast 7075 aluminum alloy spinning tubes,and the optimized combination of process parameters are obtained: the reduction is 1.8mm,the preheating temperature is 300℃,the feed ratio is 0.2mm/r and the friction condition is smearing graphite.(3)The effect of heat treatment on the mechanical properties of as-cast 7075 aluminum alloy spinning tubes was obtained.the results show that: with the increase of solution temperature,the tensile properties and Vickers hardness of tubes increase first and then decrease;with the increase of solution holding time,the tensile properties and Vickers hardness of tubes also showed a trend of increasing first and then decrease.When the solution treatment scheme is 460℃?60min,the mechanical properties of the as-cast7075 aluminum alloy spinning tubes reach the best,and the tensile strength,yield strength,elongation after fracture and Vickers hardness were 561.1MPa,474.4 MPa,17.3% and183 HV respectively.