| xSW-CNTs/AZ91D(x=0wt%,0.5wt%,1.0wt%,1.5wt%)composite wires were prepared by high energy ball milling,reciprocating extrusion and forward extrusion using atomized spherical powder of 40?m AZ91D alloy and single-walled carbon nanotubes(SW-CNTs).The effect of SW-CNTs content on the microstructurc and properties of the composite wires were studied.The strengthening and toughening mechanism and friction and wear mechanism of the composites were analyzed.WAAM samples were prepared by Wire Arc Additive Manufacture(WAAM),and the effect of SW-CNTs content on the microstructure and properties of WAAM samples were compared.The microstructure and mechanical properties of the composite wires and WAAM samples were investigated after solution at 420? for 4 h and aging at 200? for 2 h,4 h,6 h or 8 h.The main conclusions are as follows:(1)The SW-CNTs/AZ91D composite wires are composed of ?-Mg,?-Mg17Al12 phases and SW-CNTs.The grain size of ?-Mg matrix is 1?10 ?m,the distribution of SW-CNTs is relatively uniform,and the surface structure is less damaged;When the SW-CNTs content is 0.5wt%,the hardness,tensile strength,yield strength and elongation of the composite wires are the best,reaching 101.7 HV5,341.4 MPa,251.0 MPa and 7.6%respectively.The strengthening mechanism of SW-CNT to the matrix is mainly Orowan strengthening and load transfer strengthening.(2)The 0.5wt%SW-CNTs/AZ91D composite wire is subjected to solution at 420? for 4 h and aging at 200? for 2 h,4 h,6 h or 8 h.Compared with the composite wire without heat treatment,The microstructure and matrix grain size have not changed significantly.The elongation of solution for 4 h+aging for 2 h was the highest,reaching 8.2%.After 4 h solution+6 h aging,the hardness,tensile strength and yield strength of the composite wire reached 108.6 HV5,379.2 MPa and 277.1 MPa,but the elongation was reduced.(3)In the process of friction and wear,the addition of SW-CNTs can effectively improve the wear resistance of AZ91D matrix alloy.When the load is 10 N and the rotation speed is 336 r/min,abrasive wear and adhesive wear occur in the matrix alloy.With the increase of SW-CNTs content,the wear mechanism is mainly abrasive wear.Under low load and rotation speed,the AZ91D matrix alloy and 0.5wt%SW-CNTs/AZ91D composite material mainly exhibit abrasive wear.With the increasing of load and rotation speed,the degree of adhesive wear increases,and a small amount of fatigue wear appears.(4)The microstructure of the WAAM samples is still composed of ?-Mg,?-Mg17Al12 phases and SW-CNTs.The WAAM samples without SW-CNTs have relatively larger ?-Mg matrix grains.After wire arc additive manufacturing,the SW-CNTs are evenly dispersed and the damage is small;when the SW-CNTs content is 0.5wt%,the comprehensive mechanical properties of the WAAM samples are the best,and the hardness,compressive strength,yield strength and compressibility are 80.9 HV5,350.0 MPa,220.1 MPa and 21.0%respectively.(5)The WAAM sample of 0.5wt%SW-CNTs/AZ91D composite wire is subjected to solution at 420? for 4 h and aging at 200? for 2 h,4 h,6 h or 8 h.Compared with the WAAM sample without heat treatment,the phase composition has not changed,but the grain size of matrix have grown;the mechanical properties of WAAM sample are the best after 4 h solution+2 h aging treatment.At this time,the hardness,compressive strength,yield strength and compressibility are 86.8 HV5,359.3 MPa,103.5 MPa and 22.6%respectively.(6)Conduct electrochemical performance tests on SW-CNTs/AZ91D composite wires and WAAM samples respectively,When the content of SW-CNTs is 1.0wt%,the electrochemical corrosion resistance of composite wires and WAAM samples is the best. |
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