Design And Process Research Of Friction Stir Extrusion Based On Threaded Probe

Friction stir technology is an advanced manufacturing technology that has developed rapidly in the past 30 years.Its advantage lies in the flow molding of metal that drives plasticization.Melting does not occur during the forming process,the material remains in a solid phase state,and the material is vigorously mixed and agitated during the forming process.Therefore,the friction stir technology not only plays a role in the field of welding,but also has broad application prospects in the field of composite material preparation.Based on the friction stir extrusion method of agitating needles,the effects of stirring tool and process parameters on friction stir extrusion were studied by self-made equipment.The friction stir extrusion mechanism was explored and analyzed.The study found that:1?In the friction extrusion process based on the stirring needle,the two solutions proposed by the subject can both extrude the material.Scheme 1 is based on the idea of increasing the downward migration of metal.After preheating the material in the mold,the extrusion test is carried out by using four kinds of stirring needles with different structural shapes.The results show that the cone stirring head can drive plasticized metal more stronger than the blade type stirring tool,the two-stage stirring tool and the three-stage stirring tool.Scheme 2 is based on the idea of suppressing metal reflow.By providing a heating module at the extrusion end,the resistance of metal migration is reduced,and the extrusion test is carried out by using a conical stirring head in the first scheme.The results show that a well-formed,densely packed extruded material can be obtained at different feed rates.By adding graphene to the aluminum matrix,a well-formed metal matrix composite material was successfully prepared,and the related technical problems were initially solved.2?There are three stages in the friction stir extrusion process: feed filling stage,compaction deformation stage and extrusion forming stage.During the feed filling phase,the mold temperature rises slowly.As the accumulation of materials in the mold increases,the high-speed friction between the stirring head and the material in the mold causes the temperature of the mold to rise sharply during the compaction deformation stage.When the pressure value at the end of the stirring needle breaksthrough the pressure required for metal flow,the material is extruded from the mold.3?This subject also studies the friction stir extrusion mechanism of aluminum alloy.The results show that there are two kinds of stirring behaviors in the friction stir extrusion process,one is caused by the periodic vibration of the edge of the stirring needle,and the material morphology after stirring is regular stacked topography.The other is the stirring of the inside of the spiral groove of the stirring needle due to excessive accumulation of materials,and the shape of the material after stirring is eddy.And the metal in the spiral groove has a certain degree of impact on the surrounding metal.4?It has also been found that during the extrusion process,the process of feeding the material into the spiral groove of the stirring needle is a two-way pressure process.When the spiral groove moves downward,the spiral groove edge will squeeze the plasticized metal to migrate downward.At the same time,the lower teeth of the spiral groove will have a gap in the process of moving downward,and the mixing needle is surrounded by plastic.The metal will flood into the gap,creating an upward squeezing of the plasticized metal that is blown into the spiral groove.