| 2XXX aluminum alloy has been widely used in the field of Aeronautics and Astronautics.With the development of advanced aerospace equipment,higher requirements for the comprehensive performance of 2XXX aluminum alloy have been required.A series of new 2XXX aluminum alloys were developed by means of component optimization and preparation process.This paper mainly studies the influence of secondary extrusion on the microstructure and properties of 2024 aluminum alloy,the researches mainly included three parts:(1)The effect of the homogenizing anneal on the structure and properties of the ingot and the first extrusion sample,(2)The effect of the secondary extrusion on the microstructure of the 2024 aluminum alloy,(3)The effect of the secondary extrusion the properties and structure of the 2024 aluminum alloys in the T4 and T6 state.The main results are as follows:(1)When homogenized at 495? for 4-24 hours,the residual phases percentage area both in the as-casting and first extrusion samples decrease with the elongation of the holding time.The residual phase percentage area in the as-casting samples decrease from 9.3%to 3.2%as the holding time increased to 16 hours,further elongation the holding time the residual phase almost unchanged.The residual phase percentage area in the first extrusion samples decrease from 9.3%to 3.5%as the holding time increased to 8 hours,further elongation the holding time the residual phase almost unchanged.(2)After secondary extrusion,fiber structure still distribute along extrusion direction of different samples,while the residual phase is further broken and the average size decreases obviously.(3)On a certain solution condition(500?/30min),the area percentage and the average size of the residual phase decreased again.The percentage of residual phase area of the first extrusion samples decreased to 4.4%and the average size of residual phase reduced to 2.6 ?m after soluted at 500?for 30 minutes.The residual phase area percentage of secondary extrusion samples decreased to among 2.6%-6.4%and the residual phase average size of secondary extrusion samples reduced to between 2.3 ?m-2.7?m after soluted at 500? for 30 minutes.(4)On a heat treatment condition of soluted at 500?for 30 minutes and aged at 185? for 12 hours,the mechanical property of the secondary extrusion samples is higher than of the first extrusion sample.After secondary extrusion,the yield strength increase from 373.5 MPa to the region of 382.3 MPa and 387.7 MPa,the tensile strength increase from 475.7 MPa to the region of 478.9 MPa-493.4 MPa and the elongation increase from 14.4%to the region of 15.7%-18.1%(5)On a heat treatment condition of soluted at 500? for 30 minutes and natural aged for 90 days,the mechanical property of the secondary extrusion samples is also higher than the first extrusion sample.After secondary extrusion,the yield strength increase from 345.9MPa to the region of 351.7MPa and 368.9MPa,the tensile strength increase from 480.7MPa to the region of 500.7MPa-510.9MPa and the elongation increase from 15.8%to the region of 17.5%-21.7%... |
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