| In recent years,With the rapid development of my country’s economy,many aspects have put forward higher standards for the performance of materials.The emergence of SiCp/Al composite material provides the possibility to meet this demand,but the addition of reinforcing phase in the aluminum matrix composite material makes the thermophysical properties of it and the base aluminum alloy differ greatly,resulting in poor weldability..There are problems such as difficulty and low joint performance when welding such materials by traditional fusion welding methods,which limit the engineering application.In this paper,SiCp/6061-T6 aluminum matrix composite is used as the base material,and the friction stir welding method is used to connect it.The friction stir welding process and mechanism of the obtained welded joint are studied,the appropriate welding speed and the rotating speed of the stirring head are selected,and the properties and microstructure of the joint are analyzed.On the basis of previous experiments,the friction stir welding joints with good performance were subjected to T6 heat treatment,and the heat treatment process was explored while optimizing the welded joints.The microstructure,microhardness,tensile strength,SEM-EDS micro-area composition,fracture morphology and XRD phase types of welded joints under different welding processes were analyzed respectively.The research indicates show that the welding speed and the rotating speed of the stirring head have important effects on the macroscopic morphology,microstructure and mechanical properties of the welded joint,and the influence of the pressing depth of the stirring head is relatively small compared with the former two.When the welding speed is 25 mm/min and the rotating speed of the stirring head is 1400 r/min,the welding seam is well formed,and the tensile strength is the highest,which is 164.4 MPa;when the rotating speed of the stirring head is 1000 r/min,the fixed value,the tensile strength of the welded joint first increases and then decreases with the increase of the welding speed,and the microhardness increases with the increase of the welding speed;when the welding speed is a fixed value of 30 rmm/min,the tensile strength of the welded joint increases with the stirring The increase of head rotation speed first increased and then decreased,and the microhardness increased with the increase of stirring head rotation speed.Depression depths of 4.3 mm and 4.4 mm are sui Tab.for the process chosen in this paper.The fracture mechanisms of welded joints under different processes are mainly microporous aggregate fracture,transgranular fracture + intergranular mixed fracture.The microstructure of welded joints is mainly divided into base metal,heat-affected zone,heat-mechanical affected zone and weld nugget zone.Its macroscopic morphology presents an "onion ring" structure,and the hardness distribution curves of all welded joints present a "W"-shaped state.The hardness value in the heat-mechanical affected zone is the lowest;while the grains in the weld nugget zone are small and uniformly distributed,and the hardness in this region is the highest.After welding,the welded joint is subjected to T6 heat treatment,that is,520℃×2h solution treatment+water quenching++180℃×9h aging treatment: Under this process,the microhardness and tensile strength of the welded joint areincreased to a certain extent.When the welding speed is 25 mm/min and the speed of the stirring head is 1400r/min,the tensile strength of the joint is 289.48 MPa,and the strength coefficient reaches 80.41 % of the base metal;the speed of the stirring head is 1800 r/min,and the welding speed is 30 mm/min.min,the tensile strength of the joint was 239.53 MPa,and the strength coefficient reached 66.54 % of the base metal;the hardness and microstructure distribution of the joint did not change before and after heat treatment,the precipitation phase Mg2 Si in the joint was transferred,and the element segregation was improved.38 Fig.s,10 Tab.s,and 102 references. |
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