Effect Of Extrusion Process On Mechanical And Electrical Properties Of 2297 Aluminum Alloy

In this paper,2297 alloys containing trace amounts of Ce,Ca and Y elements were prepared by conventional casting method.The microstructure and mechanical properties of as-cast,homogeneous,extruded,solid solution and micro-alloying were studied The microstructures were analyzed using X-ray diffraction(XRD),optical microscopy(OM),scanning electron microscopy(SEM),micro-hardness testing,room-temperature mechanical property testing and conductivity testing,respectively.And the effects of extrusion ratio,solution process,aging time and micro-alloying on the mechanical properties and electrical properties of the alloy were analyzed.The analysis of the as-cast microstructure,homogeneous microstructure and mechanical properties of the experimental alloys show that the as-cast microstructure was mainly composed of equiaxed grains and coarse Cu-rich phases at grain boundaries,and there was obvious elemental segregation phenomenon;After the homogenization treatment performed at 520°C at different times,the non-equilibrium eutectic phase in the alloy structure dissolves into the aluminum matrix,dendrite segregation is improved,the grain boundary becomes clearer,and the best homogenization process is 520°C×24 h,the micro-hardness is from 86.3 HV drops to 70.7 HV,the elongation from 4.4% to 9.2%,which is favorable for subsequent hot working.By studying the effect of extrusion ratio on the microstructure,micro-hardness and electrical properties of the alloy,it can be shown that with the increase of the extrusion ratio,the original coarse grains of the alloy gradually became elongated along the extrusion direction.In the fibrous grains,the micro-hardness of the alloy increased gradually with the increase of the extrusion ratio,but the change was not significant;however,the electrical conductivity gradually decreased with the increase of the extrusion ratio.By optimizing solution treatment system of the alloy and exploring the effect of aging time on the mechanical properties and electrical properties of the alloy,it was shown that with the temperature or the solution time increasing the second phase gradually dissolved into the aluminum matrix,and the fibrous structure left by the extrusion also gradually decreased;the tensile strength,yield strength,micro-hardness and electrical conductivity gradually increased,and the elongation rate gradually decreased,if the experimental alloy was solid-dissolved at 480°C-520°C for 1.5 hours,or at 520°C for 0.5-1.5 hours.The alloys with different extrusion ratios exhibited the same response in the solution treatment.With the increase of the extrusion ratio,the ability of the second phase to dissolve the aluminum matrix was stronger,and the value of tensile strength,yield strength,and the micro-hardness were better,while the elongation and conductivity were lower.As the alloy with the extrusion ratio of 61 was treated with solution at 520 °C for 1.5h and aging at 190°C for 24 h,the tensile strength,yield strength,elongation,micro-hardness and electrical conductivity were 332 MPa,240 MPa,13.52%,126 HV and 28.73% IACS,respectively.The alloy with an extrusion ratio of 61 was aged at different times at 190°C.As the aging time prolonged,the precipitation phase gradually increased,and the tensile strength,yield strength,and micro-hardness gradually increased;further prolonging the time,and the tensile strength.The yield strength and micro-hardness showed a decreasing trend;the conductivity continued to increase over time,while the elongation rate showed a downward trend.By studying the effect of micro-alloying on the microstructure and properties of the alloy,it was shown that the addition of 0.15 wt.% Ce,0.16 wt.% Ca,0.03 wt.% Y alloys can refine the as-cast alloy grains and produced many second phases in grain boundaries.After homogenization at 520 °C for 24 h,the intragranular segregation was improved and the micro-hardness was decreased,which is favorable for the subsequent hot-working process.After the solution aging treatment,the elongation and electrical conductivity of the experimental alloy are improved.The elongation and conductivity of the alloy of 0.15 wt.%Ce with an extrusion ratio of 61 reached 21.25% and 38.26% IACS,respectively.