| The phase structure and phase transformation of titanium and titanium alloys are the most basic research in the field of titanium alloys.Since the discovery of titanium,scholars have been studying the related mechanism continuously.However,the results show that the titanium is not similar to other titanium elements(Zr,Hf),which conforms to the phase transition rule of one electron theory,and still can't obtain the metstable beta-Ti in ambiant condition.In addition,some aerospace components msde by titanium alloy entrance phase transition under pressure,resulting in brittle phase and posing a safety hazard.Therefore,the study of phase structure and phase transition of titanium has high research value in scientific theory and application technology.This paper adopts two ways to get the metastable phase structure of titanium by changing the parameters of the experimental conditions.One is magnetron sputtering film and the other is laser shocking.The XRD,TEM,SEM,EDS,XPS is used to detect the condition and process of titanium transformation.The results of the experiment are as follows:In magnetron sputtering experiment,we prepared a series of epitaxial growth of titanium thin films on SiC single crystal substrates and under different conditions.Controlling the substrate temperature is 500?,the sputtering power is SOW,titanium thin films,which is measured by XRD and TEM,with thickness of 50 nm is fcc structure and 100nm is hcp structure.It demonstrates that the thin film transformed from fcc to hcp structures with increasing the thickness,which is mainly casued by the increase of the thickness of membrane layer can lead to the distortion of the mismatch between the substrate and the film layer and can not be sufficient to maintain the stable existence of the fcc-Ti and leads to the conversion of the fcc-Ti to the ambiant stable alpha-Ti.The alpha Ti(1011)is existed in 100nm thin film,which is not comply with the provisions of the epitaxial structure and the(0002)peak position is depart from the block of ?-Ti.Therefore,we consider that the peak position of(1011)is the intermediate state of the fcc hcp transformation.In addition,the temperature of the substrate and the sputtering power affect the membrane structure.In the laser impact experiment,pure titanium plates with purity of 99.995%obtained the phase structure transformation of alpha to omega in different impact parameters.The increase of laser energy has little influence on the omega transition,while incresing the pulse width and impact frequency can promote the transformation of alpha to omega in a certain range.Comparing the influence of original texture to the transition,the thermal processing state and annealing samples at 650?,under 4J-15ns conditions,it is found that the thermal processing state is beneficial to the phase transition because of the more plastic deformation in it.The 99.95-Ti samples shocked in the condition of 4J-15ns and repeated impact,got through transition of alpha to omega and to fcc.Increasing with the number of shocks,the content of fcc-Ti increased firstly and then decreased.It is attribute to the the presence of impurities,especially the oxygen,suppresses the ??? transition by increasing both the ? energies relative to a and the energy barriers of the transformation.Comparing the response of the two purity samples to the laser impact under the same impact parameters(4J-15ns),it was found that the higher the purity,the better the transformation of alpha to omega. |
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