Effect Of Heat Treatment With Pulse Current On Aging Microstructure And Mechanical Properties Of Al-Cu-Mn-Zr-V Alloy

As a typical high-strength casting aluminum alloy,Al-Cu casting alloy has high specific strength,excellent high-temperature properties and processing properties,and is widely used in aerospace,military and civil industries.With the continuous development of science and technology,people put forward higher requirements on the comprehensive performance of aluminum alloys,and the comprehensive performance of Al-Cu cast alloys can be greatly improved by suitable heat treatment process.In this paper,we studied the effect of adding pulse current to solution treatment and aging treatment separately or jointly on the aging organization of the alloy by OM,EDS,SEM,TEM and XRD,and analyzed the mechanism of the effect of pulse current in different stages of heat treatment.In the solid solution treatment of Al-Cu-Mn-Zr-V alloy,pulse current with different parameters was applied,and it was found that the pulse current could promote the movement of solute atoms in the solid solution process,and promote the precipitation of the precipitated phase in the aging Process by increasing the supersaturation of the specimen,so that the size of the precipitated phase was reduced,the number was increased and the distribution was diffused,and the thermal effect generated by the current was too large to produce superheating in the specimen,and the precipitated phase The coarsening,the improvement of Al-Cu-Mn-Zr-V alloy organization and properties by pulse current solution treatment reached the peak at 1%duty cycle,and the tensile strength of the specimen was 377.0 MPa,the elongation was 5.9%,and the hardness was 141.2 HV,respectively,the tensile strength,elongation,and hardness were increased by 29.6%,5.4%,and 47.8%compared with the heat treatment without pulse current.By adding Pulsed currents with different parameters to the aging treatment of Al-Cu-Mn-Zr-V alloy,it was found that pulses current could increase the probability of leap in vacancies during aging and promote the nucleation and precipitation of precipitated phases by promoting the formation of GP zones,resulting in a decrease in the size,an increase in the number and a diffuse distribution of precipitated phases,and a stacked distribution of precipitated phases when the current density and duty cycle were too large.The improvement of Al-Cu-Mn-Zr-V alloy organization and properties by pulse current aging treatment reached the peak at the current density of 15 A/mm²,and the tensile strength of the specimen was 444.6 MPa,the elongation was 8.4%,and the hardness was 178.5 HV.Compared with the conventional heat treatment,the tensile strength,elongation,and hardness were improved by 52.8%,50%,and 50%,respectively.The tensile strength,respectively,elongation and hardness were improved by 52.8%,50%and 86.9%compared with the heat treatment without pulse current.Based on the results of the experiments of solution treatment with pulse current and aging treatment with pulse current,using the orthogonal experimental method to add pulse current to both the solid solution and aging Processes of Al-Cu-Mn-Zr-V alloy,it was found that the effect of pulse current solution treatment on pulse current aging treatment was suppressed,and the number of precipitated phases was significantly reduced,but the size of the precipitated phases was decreased,which had a limited effect on the improvement of the tensile strength of the material,but The elongation of the material was improved to a large extent.The mechanical properties of the material reached the peak when the specimens were subjected to pulse current solid solution and aging treatment using the optimum pulse current parameters,and the specimens showed a tensile strength of 395.6 MPa,an elongation of11.3%,and a hardness of 153.3 HV,which increased the tensile strength,elongation,and hardness by 35.9%,101.8%,and 60.5%,respectively,compared with the heat treatment without pulse current.TEM analysis shows that the addition of pulse current during solid solution treatment,aging treatment and solid solution-aging treatment of Al-Cu-Mn-Zr-V alloy can significantly reduce the size and substantially increase the number of intracrystalline precipitated phases,and pulse current suppresses the transformation ofθ″（Al₂Cu）phase toθ′（Al₂Cu）phase during aging,improves the co-grid relationship between the precipitated phases and the matrix,causes greater The lattice distortion is improved,and the width of precipitation-free precipitation zone（PFZ）is reduced,which improves the mechanical properties of the alloy.