Research On The Preparation And Microstructure Evolution Of Low-Density Aluminum Base Alloys

Aluminum base composites have a wide-range application prospect in the areas such as aerospace, military, automobile, electronic information and high-speed machinery, and so on, due to their outstanding properties, of which are high specific strength and modulus, high wear resistance, high damping and thermal conductivity, low coefficient of thermal expansion, and so on. With the improvement of technology, some aluminum base composites have been commercialized and used widely in the above-mentioned areas, providing strong supports to the development of the industry.Aiming at enhance specific strength and modulus of aluminum alloys, a phase transformation and diffusion combined line by PM to obtain low-density composite has been employed. The bulks of Al-15% Mg alloy, Al-15% Mg-x% Cu alloy, Al-23% Ti alloy have been formed through vacuum hot-pressing sintering, and the final reasonable process parameters of Al-15% Mg alloy have been determined through the method of trials and errors. The effects of the mechanical alloying on powder have been discussed. XRD (X-Ray Diffraction) and EDS (Energy Dispersive Spectrometer) are used to characterize the microstructure of the aluminum alloy prepared by different processes. The in-depth analysis on the formation process and characteristics of the microstructure during the diffusion of transformation has been conducted. The mechanical properties of the aluminum alloys have been measured through compression test.The deformation, fracture, cold-welding and atomic inter-diffusion have been happened repeatedly on the powders due to the collision and extrusion of the balls during the course of mechanical alloying. It can be ascertained that phase-transformation has happened in Al-Mg powder from the change of XRD diffraction patterns. The adding of Cu element can delay the alloying rate.EDS and XRD analysis show that the inter-diffusion of two kinds of powders has happened during the hot-pressing process. At first,γphase forms in the edge of Mg particles and then transforms intoβ-phase by the diffusion. The process continues from external to the internal of Mg particles until all theβ-phase forms. The generation ofβ-phase in the materials alloy can improve the strength. But if the temperature decreases,β-phase particles with extremely fine scale precipitation will weaken the properties of the material. The mechanical properties of materials can be improved through the solution treatment.The measurement to the mechanical properties of the samples show that low-density high magnesium aluminum alloy demonstrates, high strength good plasticity and toughness. The compressive strength of the Al-15% Mg with compacted degree of 98% reaches 420.9MPa. And its density is only 2.46g/cm3. However, the compressive strength of Al-15%Mg-x%Cu alloy, with the introduction of the Cu element and heat treatment reaches 695MPa. Its theoretical density is only 2.5g/cm3. Its specific strength increases remarkably.