Study On Microstructures And Mechanical Properties Of Heat Resistance Aluminum Alloy 2618

Twelve kinds of alloy 2618 containing different percents of elements were prepared using different melt-treatment processes. The microstructures of these alloys at various states were evaluated using optical microscopy, scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The room and elevated temperature mechanical properties as well as the compress creep properties of these alloys were studied systematically using Brinell hardness and INSRON tensile test apparatus as well as Gleeble-1500 heat simulating apparatus. The main contents and results are as follows:The precipitating phases with the characteristics of uniformity and dispersion could be obtained in alloy 2618 through thermo-mechanical aging treatment. The width of precipitate free zone in the alloy was decreased apparently. The room temperature tensile properties of the alloy increased by 10~17% and elongation decreased remarkably after thermo-mechanical aging treatment with 11-16% compress deformation. The heat-resistant properties of alloy 2618 could be improved using thermo-mechanical aging treatment.The coarse needle-like or nubby Al9FeNi phase existed in the cast microstructure of high content Fe and Ni alloy 2618(2#). After hot extrusion, it was broken into coarse multi-angle Al9FeNi particles. The contents of Fe and Ni have no effect on aging characteristic and the hardness of the alloy after aging. The coarse Al9FeNi phase in alloy 2618 could be broken better after the alloy was suffered larger quantity and high rate as well as multi-direction deformation at lower temperature.In the cast of alloy 2618, there existed structure inherits phenomena of coarse A^Fe and AlgFeNi phases, which were in Al-Fe master alloy and alloy 2618 respectively. The structure inherits could be eliminated when the alloy was over-heated at 960 癈 for about 30min. The elevated temperature and room temperature tensile properties of the alloy could be enhanced remarkably at the same time.After melt over-heat treatment, the uniformly and little needle-like Al9FeNi phase was obtained in the ingot of high content Fe and Ni alloy 2618 alloyed with zirconium (4#). The Al9FeNi phase was in the form of little particles after heat extrusion. Due to the retard effect of little Al3Zr particles to the recrystallization, the grain structure of alloy 2618 wasvery small. The elevated temperature tensile properties and elongation of the alloy could be enhanced apparently at one time. After melt over-heat treatment on high content Fe and Ni alloy 2618 alloyed with zirconium and manganese(5#), the small Al9FeNi particles were also obtained after it was heat extruded. The precipitate phases were smaller and the width of precipitate free zones(PFZ) in the alloy was narrower due to the effect of manganese. The room and elevated temperature tensile properties of the alloy were enhanced obviously at the same time.The Al3Ti particles in Al-5 Wt %Ti master alloy were small and uniformity after severely extrusion deformation. When the addition amount of titanium in the form of this master alloy was smaller than 0.5wt%, titanium made the grain structure of cast alloy 2618 very smaller. A large amount of dispersive Al3Ti particles retarded intensively the recrystallization and the grain growth of the alloy, so the grain size of the alloy after hot-extrusion and quench were smaller evidently. The alloying effect of titanium could increase remarkably the elevated temperature instantaneous tensile properties of the alloy at 250 C and that of the alloy which was exposed at 250C for 100 hours.The very little A1N particles were distributed evenly in alloy 2618 after stirring casting using intermixture of sub-micrometer A1N particles and complex solvent, which were mixed with high-energy ball mill. The grain sizes of the alloy (12#) after hot extrusion and quench aging were remarkably decreased due to the existence of these A1N particles. The addition A1N particles could increase remarkably the elevated temperature instantaneous tensile properties of the alloy at 250C...