Trace Ce And Heat Treatment Of Al - Cu - Li - Mg - Ag - Zr Alloy Organization And Performance

The aluminum-lithium alloy is an ideal structural material for aerospace industry, the research and development of high performance aluminum-lithium alloys is still an attractive topic of the aluminum alloy.The objective of this thesis is to study the effects of small addition of rare earth element Ce and heattreatment on microstructures and mechanical properties of Al-Cu-Li-Mg-Ag-Zr alloy which has some theoretical and practical significance to the research and development of high-performance rare earth aluminum-lithium alloy.Various tests were used, including tensile test, hardness test, conductivity measurement, optical microscope（OM）, X-ray diffraction（XRD）, transmission electron microscope（TEM）, scanning electron microscope（SEM） and Energy dispersive X-ray Spectroscopy（EDX） analysis. The heat treatment regimes were optimized by analyzing the experimental results. The conclusions can be summarized as following:1. The proper solution heat treatment for Al-Cu-Li-Mg-Ag-Zr alloy is520℃/30min. Under this condition, tensile strength, yield strength, hardness and elongation of the alloy are566MPa,512MPa,148HB and8.23%, respectively. SEM observation shows that after solution treatment at520℃for30minutes, there are still some residual particles exsited in the matrix, the main kind of the particles are Al₂Cu, fewness Al₇Cu₂Fe particles can be observed. The favorable aging temperature for T6temper and T8temper are chosen through the test,180℃for T6and150℃for T8, respectively.2.0.3wt%Ce addition can improve the tensile strength of Al-Cu-Li-Mg-Ag-Zr alloy significantly and restrain recrystallization in the process of solution treatment to some extent. On the other hand, minor Ce addition makes the delamination structure of the alloy thinner which can change the fracture mode of alloy and thus decrease the tendency of intergranular fracture. Fracture toughness of the alloy can be improved by adding trace Ce. 3. Adding trace Ce dose not change the types of main precipitates of the alloy. The main precipitates of the alloy are T1phase and θ’phase. Minor Ce addition can promote the nucleation and precipitation of T1phase and make it distribute more dispersively and homogeneously in the matrix. A cubic phase were observed in all alloys under T6peak aging condition, A competition precipitation relationship between T1phase and cubic phase could be drawn from the cubic precipitation character.