| On the basis of the domestic and foreign research present situation and the National Natural Science Fund project,Al-0.2Ag-0.2Sc-0.1Zr(wt.%)alloy wires prepared by continuous rheo-extrusion and two kinds of thermomechanical treatment were studied to develop the new heat resistant aluminum alloy wire.The results are as follows.(1)Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wires with excellent surface and microstructure were successfully prepared by continuous rheo-extrusion machine,when pouring temperature was 730℃.The tensile strength of Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wire was 78.97±3.92 MPa and the conductivity was 53.01± 1.92%IACS.(2)The refinement mechanism of Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wire with AC-Conform was obtained,① Microstructure evolution of Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wire in the cavity by AC-Conform was obtained.A lot of dislocations were formed in the deformation,and the dislocations were pinned by the second phase particles(Al3(Sc,Zr),AlAg2),which accelerated the formation of the low angle grain boundary.Along with the deformation continue,the dislocation was gathered near the small angle grain boundary and then high angle grain boundary was formed while the low angle grain boundary was formed constantly.Grain was refined.The main cause of grain refinement was the continuous dynamic recrystallization of the wire·② Influence of Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wire precipitates(Al3(Sc,Zr),AlAg2)on AC-Conform was obtained.For the second phase particles of the smaller scale,the internal second phase particles of the Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wire can promote the continuous dynamic recrystallization.③ After wire was pressed 5 passes of AC-Conform,the tensile strength was 125.98±6.78MPa while the elongation was 38.2±4.5%.CoMPared with the continuous rheo-extrusion state of itself,the tensile strength increased by 59.52%,and the elongation decreased by 9.5%.CoMPared with pure aluminum which was pressed by 5 passes of AC-Conform,the tensile strength increased by 28.39%and the elongation decreased by 15.5%.(3)Influence of the heat treatment and cold drawing of Al-0.2Ag-0.2Sc-0.1Zr extrusion(wt.%)by continuous rheo-extrusion was obtained.①With the increase of the solution time,the grain growed and the second phase particles completely dissolved.Meanwhile,the tensile strength of the wire gradually decreased,while the conductivity was slowly decreased and then stable after a small amplitude rise.②With the increase of aging time,the grain growed up slowly,and second phase particles(AlAg2,AlAgScZr complex phase)separated out.Meanwhile,the tensile strength was rising rapidly and then stability,conductivity increased rapidly and reached a plateau.③ The addition of Ag can increase the tensile strength while the conductivity was sacrificed in a small scale.④ With area reduction increasing,the grain was elongated along the direction of drawing,and then fiber structure was formed.Meanwhile,the tensile strength was rising rapidly,and conductivity decreased.⑤Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wires with 4mm diameter ware prepared via 630℃x72h solution treatment,380 ℃ x48h aging treatment and multi-pass drawing.The final performance was good.The electric conductivity reached 58.2610.33%IACS,and the tensile strength was 228.06±L6.23MPa while the elongation was 5.4±1.02%.After the wire was tested in 230℃×1h and 400℃×1h Tensile residual ratio was 97.64%and 91.78%,respectively.Al-0.2Ag-0.2Sc-0.1Zr(wt.%)wires with 4mm diameter were better than standard AT2、AT4 of IEC 62004-2007<Standard for heat resistant aluminium wire conductors for overhead conductors of the International Electrical Commission>. |
