Effect Of Al-Ti-C/B Master Alloys On Grain Morphologies And Extrusion Behavior Of Wrought Aluminum Alloys

Because of high specific strength,specific stiffness,and good processing properties,Aluminum alloys have promising applications in fields of mechanical manufacture,track tranffic,aerospace.Recently,with the transformation upgrading and lightweighting of materials,the requirements for mechanical properties are higher and higher.It’s widely known that grain refinement can effectively reduce casting defects,improve microstructure uniformity and mechanical properties of A1 alloys.Nowadays,Al-Ti-B and Al-Ti-C are the most widely used grain refiners in Al alloys.Since Al-Ti-C can effectively avoid some problems of Al-Ti-B in industrial application,it is considered to be a more promising master alloy.This paper studies the effect of Al-Ti-B or Al-Ti-C master alloy on the microstructures and mechanical properties of 2024 alloy.Otherwise,Al-Ti-C master alloy was chosen as the grain refiner of 2024 and 6063 alloys,and the correlation between grain size of cast ingot and extrusion behavior was studied.The main research results of this paper are as follows:(1)The effect of AI-Ti-C/B on the microstructures of as-cast 2024 alloy 2024 aluminum alloy can be effectively refined by Al-Ti-C/B master alloys.The microstructure of as-cast 2024 alloy transforms from coarse dendrites to equiaxed grains when 0.2%Al-5Ti-0.25C or Al-5Ti-1B was added,and the average grain size is reduced from about 150μm to 80μm.With the addition of master alloys increasing from 0.3%to 1.0%,the grain size of 2024 is kept at about 50-60μm.In addition,the grain morphology of 2024 alloy refined by Al-5Ti-1B exhibits regular polygon in two-dimension,however,it presents irregular morphology and interlaced distribution when refined by Al-5Ti-0.25C.(2)The effect of Al-Ti-C/B on the mechanical properties of as-cast 2024 alloyThe mechanical properties of 2024 alloy can be significantly improved when Al-5Ti-0.25C or Al-5Ti-1B was added.The results show that the hardness,tensile strength and elongation of the 2024 aluminum alloy are 123.6HBW,382MPa,and 2.60%,respectively,which is increased by 7.9%,12.4%,and 69.9%,when the addition level of Al-5Ti-0.25C is about 0.3%.In addition,the improvement of ultimate tensile strength inoculated by Al-5Ti-1B is superior to Al-5Ti-0.25C,however,the improvement of elongation inoculated by Al-5Ti-0.25C is better.(3)The effect of Al-5Ti-0.25C on the extrusion behaviour of 2024 and 6063 alloysThe effect of grain size on the hot extrusion performance of 2024 and 6063 alloys was studied by using Al-5Ti-0.25C as the aluminum alloy refiner.The results show:At the same strain rate and deformation temperature,the fine grain structure corresponds the lower flow stress values;Besides,dynamic recovery and recrystallization processes occurred in different degrees,the grain size of dynamic recrystallization decreases with the initial grain size decreasing.(4)The effect of Al-5Ti-0.25C on the mechanical properties of extruded 2024 and 6063 alloysThe grain size of as-cast ingot has an important effect on the mechanical properties of materials after hot extrusion.When adding Al-5Ti-0.25C master alloy to the 2024 or 6063 alloy melt,the grain size of the ingot can be effectively refined and the mechanical properties of the extruded alloys can be improved such as hardness,tensile strength,especially the elongation.