| Al-Cu-Mg alloy with trace Ag has catched the material researchers’attention for its high mechanical performance at high temperature. Compared to the conventional A1-Cu-Mg series heat-resistant aluminum alloys, its mechanical properties was excellent above150℃. But the plasticity of high alloying high strength aluminium alloy is low, and it was easy to crack in thermal deformation process. As a result, Al-Cu-Mg alloys with trace Ag was prepared using water chilling copper mould ingot metallurgy processing which was protected by active flux. The processing map was draught through the therma compressive deformation experiments. And the effects of single aging, interrupted aging, deformation aging and stress aging on the microstructure and the properties of the Al-Cu-Mg aluminum alloy with trace Ag were investigated. This could provide basis for the formulation of hot working process as well as the heat treatment process and its industrial application.The flow behavior during hot compression deformation of homogenized A1-Cu-Mg alloy with trace Ag was studied in this paper. The results showed that, at the early stage of hot compression, the alloy was work-hardening. When the stress exceeded peak stress, the alloy was softened. And the alloy showed positive sensitivity of strain rate. The deformation activation energy of Al-Cu-Mg alloy with trace Ag was196kJ/mol, and the constitute equation of flow behavior of the alloy can be expressed as ε=1.89×1013[sinh(0.0116σ)]7.29exp(-196000/RT). Moreover, according to the processing map analysis of A1-Cu-Mg aluminum alloy with trace Ag, flow instability occured at two regions, the low temperature300～400℃with a strain rate of0.1～10s-1and the high temperature460～500℃with a strain rate of1.0-10s-1. The flow localization and the fracture were responsible for it. When the temperature was above350℃, Al-Cu-Mg aluminum alloy with trace Ag showed good plasticity, The suitable deformation condition for the alloy was385～460℃and0.001～0.003s-1, then, dynamic recrystallization will happen.The effects of single aging, interrupted aging, deformation aging and stress aging on the microstructure and the properties of the Al-Cu-Mg aluminum alloy with trace Ag were investigated using hardness test, two-bridge electric-resistivity test, mechanical properties test at room temperature, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the suitable single aging process185℃/4h, and interrupted aging improved the plasticity of alloy remarkablely. Otherwise, The elongation of time of underageing at185℃increased the initial hardness of secondary ageing and accelerated the speed of aging-hardening. When the secondary aging temperature was65℃, the dominant hardening precipitates were G.P zones with a small amount of Ω phases. The mechanical properties, hardness and strength, were lower than the peak-aged alloy of T6temper. But when the secondary aging temperature was elevated to150℃, the dominant hardening precipitates were Ω phase, and the mechanical properties of alloy also were improved.Pre-stretching before aging could improve the density of dislocation of Al-Cu-Mg aluminum alloy with trace Ag, enhance the precipitation of θ’ phase, and refine Ω phase. The pre-stretching aging for the Al-Cu-Mg aluminum alloy with trace Ag accelerated the aging process and shorten the time of peak aging. Pre-stretching of1%reduced the peak hardness and strength. As the pre-stretching amount increased more than2.5%, gradually, the peak hardness and strength increased, but the plasticity decreased.The external stress of200MPa during aging decreased the aging process of Al-Cu-Mg aluminum alloy with trace Ag and the hardness of peak aging, prolonged the time of underaging stage, retarded the precipitation and growth of Ω phase. With the effects of the external stress, the preferential oriented precipitation of Ω phase was observed. |
PDF Full Text Request