| The 2xxx series aluminum alloy with high strength,toughness and heat resistance has a significant application background in aerospace and other fields.In this paper,the traditional heat-resistant aluminum alloys(2219)and the new Al-Cu-Mg-Zn-Zr-Ti heatresistant aluminum alloy designed by theory are studied.The effects of Ti alloying,hot/cold extrusion and pre-recovery heat treatment on the microstructure and properties of 2219-xTi aluminum alloy are investigated.The effect of Ti alloying on the microstructure and properties of the new Al-Cu-Mg-Zn-Zr-Ti heat-resistant aluminum alloy is also studied.The main research contents and results are as follows:(1)The effects of adding 0,0.49,0.89(wt.%)Ti content and hot/cold extrusion on the microstructure and properties of 2219 heat-resistant aluminum alloy extruded material are studied.The results show that after 535° C×3 h solution treatment and 191° C×6 h aging,the Ti content of the three alloys after hot extrusion increases,the internal dissolved phase of the alloys increases,and the grain size decreases,the effect of increasing the room temperature strength and heat resistance are first increased and then decreased.The alloy with 0.49 Ti has the best mechanical properties,and its hardness and electrical conductivity are 130.1HV and 22.71%IACS,respectively.Compared with the alloy without Ti,the tensile strength at room temperature is increased by 62.32 MPa,reaching 364.42 MPa,and the elongation after fracture is 10.1%.The peak value of hot compression at 250°C increase by 39.87 MPa,reaching 252.76MPa;the maximum intergranular corrosion depth is 181.56?m.Compared with hot extruded materials,the strength and heat resistance of cold extruded materials are further improved.The tensile strength at room temperature is increased by 32% to 416.67 MPa,but the plasticity is decreased and the elongation after fracture is 8.6%.The peak value of the thermal compression stress at 250°C increased by 8.17 MPa,which is 230.82MPa;the maximum intergranular corrosion depth decrease by 81.09?m,which is 193.9?m.(2)The effects of two pre-recovery heat treatments(250?×6h+ 350?×6h+ 450?×2h and 250?×6h+ 350?×6h+ 450?×2h+ 500?×2h)on the microstructure and properties of high-Ti content 2219-0.89Ti-type aluminum alloy cold extrusion after 535°C×3h solution treatment and 191°C×6h aging are studied.The results show that the pre-recovery heat treatment reduces the content of undissolved phase inside the alloy,refines the grain and enhances the room temperature strength.The second pre-recovery heat treatment has the best effect,and its hardness and electrical conductivity are 150.60 HV and 23.53%IACS,respectively.Compared with the alloy without pre-recovery heat treatment,the tensile strength at room temperature is increased by 40.47 MPa,reaching 457.14 MPa,and the elongation after fracture is increased to 12.8%,the resistance to intergranular corrosion is improved,and the maximum intergranular corrosion depth is reduced from 193.90?m to 151.60?m.(3)The effects of adding Ti with 0,0.47 and 0.89(wt.%)on the microstructure and properties of the new Al-2.87Cu-3.83Mg-2.91Zn-0.2Zr-xTi heat-resistant aluminum alloy cold extrusion materials are studied.The results show that after cold extrusion,480° C×2 h solution treatment and 120?×12h aging,with the increase of Ti content,the alloy's internal undissolved phase increase,grain refine,room temperature strength and heat resistance improve.The alloy with 0.89 Ti has the highest strength,and its hardness and electrical conductivity are 160.8HV and 23.56% IACS,respectively.Compared with the alloy without Ti,the tensile strength at room temperature is increased by 25.02 MPa,reaching 49.43 MPa,and the elongation after fracture is 16.67%.The peak value of hot compression at 250°C increase by 86.57 MPa,reaching 326.66 MPa.At the same time,the alloy also has good resistance to intergranular corrosion,and the maximum intergranular corrosion depth is 146.31?m.In this paper,cold extrusion is used to replace the hot extrusion process,which greatly improves the room temperature tensile strength of 2219-0.89 Ti alloy.The tensile strength at room temperature is increased by 32% to 416.67 MPa without reducing the heat resistance of the alloy.On the other hand,a new Al-Cu-Mg-Zn-Zr-Ti heat-resistant aluminum alloy is designed innovatively,and its tensile strength at room temperature is as high as 490.43 MPa,and the peak value of thermal compression stress at 250°C reach 326.66 MPa. |
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