| Quasicrystalline is a kind of solid with periodic translational lattice structure, the atomsinside are usually arranged in order but not show the appearance of periodic translationalrepetition. The symmetry was incompatible with the space lattice (such as5axis ofsymmetry). Otherwise, the structure and physicochemical properties of quasicrystallineusually lies between crystal and amorphous materials, also have the special macroscopicsymmetry which can’t be exist in crystal. Quasicrystalline materials received extensiveattentions of researchers which were because of its unique micro structure, special meta-stablephysicochemical properties, and also potentially properties in many different regions, therelevant achievement wins the Nobel Prize in chemistry in2011. The present research ofquasicrystalline is very active all over the world, the scientists of France, Germany, Japan andthe United States have carried out related works, the properties of low friction, corrosionresistance, heat resistance and non sticky will be further developed in the next few years. Asthe second largest quasicrystalline system, the research of transmission, mechanical, surface,hydrogen storage, optical and other properties of Ti based quasicrystalline alloys have theextremely important theory and application value. Unfortunately, the quasicrystalline bulkalloys with large size are difficult to obtained by conventional method because of the pooradhesion of Ti based quasicrystalline alloys, which limits the research and application of itsmechanical, friction and wear, thermal performance and other properties directly. Therefore,how to prepare Ti based quasicrystalline bulk alloys with large size and high performance hasbecome a research focus in the field of quasicrystal material at present.In order to solve the bottleneck problem that of preparing Ti based quasicrystalline bulkalloys with large size and high performance, this work took the Ti40.83Zr40.83Ni18.34quasicrystalline materials as the object, quasicrystalline powders synthetised by mechanicalball milling and subsequent annealing process were obtained first, the Ti40.83Zr40.83Ni18.34bulksamples with different dimensions which sintered by heat treatment after forming, hotpressing, ultrahigh pressure sintering(ultrahigh pressure, ultrahigh pressure and temperature),spark plasma sintering(SPS) method were prepared. The micro structure, phase composition,mechanical properties, friction and wear properties, thermal conductivity, electricalconductivity and also magnetic properties were tested in detail, the comparison and thedisccusion also be carried on after, the basic conclusions are shown as follows: (1) Ti40.83Zr40.83Ni18.34bulk quasicrystalline samples were successfully sintered by heattreatment after forming, hot-press sintering, ultrahigh pressure (ultrahigh pressure, ultrahighpressure and temperature) and SPS. The results of XRD test shown that the samples whichsintered by all methods had the characteristic peaks of quasicrystalline (mainly for the peaksat the position of36°and39°), also high content of quasicrystalline phase and few impuritycomponents.(2) The Ti40.83Zr40.83Ni18.34quasicrystallines were easy to appear the warped, rupture anddepression and other defects. The method of hot-pressed sintering was convenient, also tendto be sintering samples with the wide dimension region, but always with low strength. Thesamples sintered by ultrahigh pressure and temperature method had the better integrity degree,and most excellent anti-friction ability, but this method may limit for its little sample size.SPS method brought about the maximum density of5.83g/cm3, which was about97.46%ofthe theory density, the hardness, compressive strength and maximum deformation ratio allshown the maximum value of716(HV),662MPa,2.65%respectively.(3) By the test of friction and wear of the samples, friction and wear behavior of sampleswhich sintered by different methods and different conditions were discussed, the frictioncoefficients of the samples sintered by five methods were0.40-0.59, the friction coefficientwould increase associated with the density, also the the strength and stiffness. In addition, thehigher pressure, the small friction coefficient would be, and tend to be stable after a certainvalue, the relationship of volume loss appears to be a linear rose within a certain range, andemergence of parabolic growth after, then stable at last. The friction rate raised the volumeloss and decreased the friction coefficient. While total time or the total displacementincreasing, the friction coefficient decreased, but when the total time or the total displacementwas not high enough, friction coefficient would be shocks in a certain region. Furthermore,when the temperature changes, if the bulk not heated while forming, the friction coefficient ofthe sample itself would be affected by temperature. Otherwise, the friction coefficient wouldnot affected.(4) Based on the optimal mechanical performance of the samples sintered by SPS method,the thermoelectric and magnetic properties were carried out. The results are shown as follow.The thermal conductivity was3.88WK-1m-1, electric conductivity was3.35×105-1m-1,Seebeck coefficient was3.26×10-6VK-1. The thermoelectric coefficient ZT at roomtemperature was2.76×10-4, which would decreased along with the increasing of temperature,the value at600℃was2.06×10-4. The results of magnetics indicated that, the coercive force was25.85(Oe), the residual magnetism was0.01emug-1，and the saturation induction densitywas0.65emug-1。... |
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