The Effects Of Ag And Mg Content On Mechanical Properties And Microstructure Of Al-Cu-Mg Alloys

As the development of aviation and aerospace technology, Al-Cu-Mg-Ag heat-resistant alloy have become one focal field in many countries’development and research. A kind of heat resistant strengthening phase precipitated on{111} in Al-Cu-Mg alloy with trace Ag. The mechanical property and good performance of high temperature were improved due to the good precipitation hardening and thermal-stability, which was the advantage of meeting the requirement of supersonic aircraft. Al-Cu-Mg-Ag alloys with different Ag and Mg content were prepared by ingot metallurgy and thermal-mechanical treatment. They were used to study the effects of Ag and Mg content on the mechanical properties and microstructures of Al-Cu-Mg-Ag alloy and optimize the component of it. The effects of Ag and Mg content on the mechanical properties and microstructures of the alloy have been studied by Wicker hardness test (HV), room temperature tensile properties, high temperature tensile properties, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to provide the basis of alloy composition optimization and industrial application.The effects of Ag content on the mechanical properties and microstructures of Al-Cu-Mg alloy have been studied by changing the Ag content of Al-Cu-Mg-Ag alloy. The results showed that with the increase of Ag content, the harden ability was higher and the hardening rate was accelerated. GP precipitation was refrained and the precipitation process changed due to trace Ag. With the increase of Ag content, the yield strength and tensile strength increased. The results of high-temperature tension test at250℃were the same as it at room temperature, but the strength kept a high value. The plasticity decreased gradually. After the solution treatment the alloys were all recrystallized to form small equiaxed grains. The main strengthening phases of Al-Cu-Mg alloy without trace Ag were0’phases and S’phases. And the main strengthening phases of Al-Cu-Mg alloy with trace Ag were Ω phase and θ’phase. With the increase of Ag content, the number of Ω phase increases gradually to make the strength increase. The trace Ag promote Ω phase to precipitate.The effects of Mg content on the microstructure and properties of Al-Cu-Mg-Ag alloy showed that with the increase of Mg content, the aging response time is accelerated, whereas the peak hardness increased at first and then decreased, so did the yield strength and the tensile strength. On the contrary, the plasticity of the alloy reduced to some extent at first and then improved. The results of high-temperature tension test at250℃showed that with the increase of Mg content, the tensile properties increased. And compared with the results at room temperature, the value of decreasing with high Mg content was lower. The result of microstructure showed that when Mg content increased to1.2%, the dendrites were finely formed and well-distributed. After the solution treatment the alloys were all recrystallized to form small equiaxed grains. The main strengthening phases in Al-Cu-Mg-Ag alloy with0.4%and0.8%Mg content are Ω phase and a small amount of0’phase. Increasing Mg content to0.8%improves the density of the Ω phase after aging treated to peak-aged stage, and makes the precipitations small and finely dispersed. When Mg content increased to1.2%, the main strengthening phases of the alloy are Ω phase and S’phase. And the density of the Ω phase decreased to some extent.