| After adding Mg element to the traditional Al-Cu alloy,an Al-Cu-Mg alloy is formed.As one of the representatives of traditional heat-resistant aluminum alloys,Al-Cu-Mg alloy is widely used in the aerospace field due to its excellent performance.The traditional Al-Cu-Mg alloy has a significant decrease in mechanical properties when it is used at temperatures above150?,so it can no longer meet the performance requirements of aluminum alloy materials in aerospace and other fields.Al-Cu-Mg-Ag alloy formed by adding trace Ag to Al-Cu-Mg alloy,which not only has excellent thermal stability,but also has higher room temperature strength and better damage resistance.This new type of heat-resistant aluminum alloy is expected to meet the heat resistance and economic requirements of the new generation of spacecraft materials,and has broad application prospects.When trace amounts of Mg and Ag are added to the Al-Cu alloy,Mg-Ag atomic clusters will be formed in the early stage of aging,and a new strengthening phase that?phase precipitate,which is the main reason that Al-Cu-Mg-Ag alloy has excellent high temperature performance.Therefore,through Vickers hardness measurement,XRD phase analysis,this paper studied that the alloys that changed the Mg and Ag content in Al-Cu-Mg-Ag alloy under a certain Cu/Mg ratio and were solution-aged,the effects of Mg and Ag on the formation of precipitated phases in the alloy and the strength and toughness of the alloy.Based on the EET theory,the microscopic nature of the influence of Mg and Ag on the precipitation nucleation and age hardening behavior of Al-Cu-Mg-Ag alloy was analyzed.The studies show that the peak aging time of Al-Cu-Mg-Ag alloy prolongs and the peak hardness decreases with the increase of Ag content,under a certain Cu/Mg ratio.Under the same Mg/Ag ratio,with the increase of Cu/Mg ratio the peak aging time of Al-Cu-Mg-Ag alloy is slightly extended,the hardness and strength are slightly reduced,and the thermal stability will be enhanced.The calculation of the valence electron structure of the solid solution in the matrix shows that Ag has the largest enrichment trend on the{111}_?plane,Mg-Ag clusters are more stable and easier to form than Mg-Cu clusters.The formation of Mg-Ag clusters on the{111}_?plane promotes the enrichment of Mg atoms,and because of the existence of Mg-Cu clusters,Cu atoms are also enriched with the Mg atoms to this plane,and then form?phase.In this process,the Mg and Cu atoms are consumed,As a result,the precipitation of the S phase is suppressed,and to a certain extent,the precipitation of the??phase is also suppressed.From the perspective of the covalent electronic structure,the?precipitated on the{111}_?plane is stronger than the S and??phases precipitated on the{001}_?plane.When dislocations meet the?phase in{111}_?motion in Al-Cu-Mg-Ag alloy,the motion resistance increases significantly.From the difference in phase electron density,the?/Mg-Ag/?interface was formed when the Mg-Ag atomic layer was present.The Mg-Ag layer changes the valence electron structure of the interface between?and the matrix?,increases the bonding force of the interface,improves the continuity and stability of the interface,and improves the strength and toughness of the alloy.Through the theoretical study of the nucleation mechanism of precipitation phases and the microscopic nature of aging hardening behavior,it has practical significance for optimizing Al-Cu-Mg-Ag alloy composition. |
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