The Preparation And Research Of Bulk Ti-Al Based Amorphous/Nanocrystalline Alloy By SPS Technology

Ti-Al based bulk amorphous alloy shows a broad application prospect in aerospace,new energy vehicles,electronics and biomedical fields with its high strength,light weight,excellent wear and corrosion resistance and good resistance to high temperature creep properties.The glass forming ability of amorphous alloy prepared by conventional technology is low,and the plasticity is poor,and reduces its application in industrial production.Therefore,It is the key to solve the problem how to prepare a Ti-Al based bulk amorphous/nanocrystalline composite material with excellent performance.In this paper,a novel bulk amorphous/nanocrystalline composite was prepared by the combination of mechanical alloying?MA?and spark plasma sintering?SPS?.First,Ti₅₀Al₄₅B₅ was researched to determine the optimum parameters.Preparation of Ti-Al amorphous powders by mechanical alloying method to research the influence of milling process on the glass forming ability.Using X ray diffraction?XRD?,scanning electron microscopy?SEM?,EDAX energy spectrum analysis,differenTi-Al scanning calorimetry?DSC?,transmission electron microscopy?TEM?to analysis phase composition,analysis of milled powder morphology,thermal stability.The amorphous powder was made a bulk amorphous alloy by spark plasma sintering,the sintering block size is?20×5 mm.And then measure the mechanical properties of samples,the density was calculated according to the Archimedes method.Test its Vivtorinox hardness,compressive strength,and using XRD,SEM and TEM test technology to determine phase structure,fracture morphology and micro structure.At last concluded the best preparation process of amorphous alloys.Next,the four element amorphous alloy was prepared by element substitution method on the basis of Ti₅₀Al₄₅B₅.The effects of different elements on the thermal stability and the amorphous forming ability of amorphous powders were studied.Analyze the effects of alloying elements on the strength,hardness and density to determine the best designed components.Choose the best composition to make heat treatment annealing to improve the mechanical properties by eliminating the residual stress.The results show that the effect of amorphous is the best when the milling time is45h and the rotational speed is 350r/min,the sintering temperature is about 10K above the T_g,the insulation time is 5min.The addition of W,Si and V elements can improve the glass transition temperature,increase the supercooled liquid region and improve the amorphous forming ability of the alloy.The Si elements has a better role on the improvement of mechanical properties,Ti50Al45B4Si alloy powder can get amorphous and nanocrystalline composite materials after sintering,and then the samples have a higher strength and hardness for the nanocrystalline phase,produceing strength and preventing the extension of shear band.The maximum hardness and fracture strength of Ti50Al45B4Si measured by experiments were 1175 and 1347MPa.After heating annealing at 500K temperature the Ti50Al45B4Si amorphous alloy's strength,hardness and plasticity is improved compared with no annealing,but the fracture mode is still a brittle failure.