Ti-47.5Al-2.5V-1.0Cr钛合金具有高温延展性好、高温强度大的特点,有用于铸造涡轮、涡流器、叶片等高温部件的潜力.在用激光诱导击穿光谱(LIBS)对合金或部件内部定量分析前,需预先将被分析钛合金样品和钛合金标准样品用相同的方法制备以去除表面氧化层、铸造反应层和污染物.鉴于该钛合金为室温脆性材料,不适于切削制备样品,宜采用磨抛方法制备样品,而磨抛制备样品时因发热粘滞会造成样品表面污染,影响LIBS分析钛合金中成分.实验用LIBS评价光谱磨样机磨制、金相磨样机磨制、手工磨制、手工抛光、辉光氩离子轰击等几种方法去除不同组织钛合金标样表面氧化层、污染物的效果.通过LIBS分析发现,样品制备过程中污染来源于制造砂纸的胶接剂,磨制线速度、磨料粒度、抛光方向影响制备效果,且样品的组织也影响污染物去除效果.用碳化硅砂纸光谱磨样机高速磨制钛合金表面碳污染层深度大,达15 μm,高于水冷金相磨样机中速磨制的碳污染层深度,说明温度高促进碳在钛合金中的扩散;中低速磨制时,使用的砂纸标号越高,含碳、钙的污染物在样品表面附着增加.中速磨制时,与α相亲和力强的钙、铝等元素在α组织的钛合金扩散深度较α+β、α2+γ组织钛合金大,钙污染深度达10 μm,而碳在不同组织的钛合金表面扩散没有明显差别.手工低速磨制时,在钛合金表面上的碳、钙污染层较浅,深度为1~3 μm,与磨痕深度一致.双向或沿磨削纹理抛光效果优于垂直纹理抛光效果,残留污染物深度不超过1 μm,与辉光氩离子轰击效果相近.实验研究解决了钛合金样品制备易受污染的问题,LIBS分析碳等元素的校准曲线得到改善,测量精度得到提高.对于Ti-47.5Al-2.5V-1.0Cr钛合金样品分析的结果同其他方法的对照结果一致性较好.%Ti-47.5Al-2.5V-1.0Cr titanium alloy has some advantages such as good high temperature ductility and strength, so it could be potentially applied to produce high-temperature components, for example, cast turbine, swirler and vane.Before the quantitative analysis of alloy or parts interior by laser-induced breakdown spectroscopy (LIBS), the samples and certified reference materials of titanium alloy should be pretreated to remove surface oxidation layer, cast reaction layer and contaminants.The titanium alloy belonged to fragile material at room temperature, so it should be prepared by grinding and polishing, but not cutting.However, the sample surface may be polluted due to the heating and stiction in grinding and polishing preparation, which would influence the LIBS analysis of components in titanium alloy.The effect of several pretreatment methods (grinding by milling machine, grinding by metallurgical milling machine, manual grinding, manual polishing and glow argon ion bombardment) on removal of surface oxidation layer and contaminants of titanium alloy reference material with different structures were evaluated by LIBS.LIBS analysis results indicated that the pollution in sample preparation process was mainly from the cement for abrasive paper production.The sample preparation was affected by linear velocity of grinding, particle size of grinding material and direction of polishing.Moreover, the removal efficiency of contaminants was also influenced by sample structure.The carbon pollution layer on titanium alloy sample surface which was ground with high speed by silicon carbide abrasive paper milling machine was deep with depth up to 15 μm, which was higher than that of the sample which was ground by water cooling metallurgical milling machine with intermediate speed.It indicated that the high temperature could accelerate the diffusion of carbon in titanium alloy.During grinding at medium and low speed, the absorption of carbon and calcium pollutants on sample surface increased with the increase of mark number of abrasive paper.In medium speed grinding process, the diffusion depth of elements such as calcium and aluminum with good affinity to α phase in titanium alloy with α structure was higher than that of titanium alloy with α+β and α2+γ respectively.The pollution depth of calcium was up to 10 μm.However, the diffusion of carbon on the surface of titanium alloy with different structures showed no significant difference.During manual grinding at low speed, the pollution layer of carbon and calcium on titanium alloy surface was shallow with depth of 1-3 μm, which was consistent with the grinding crack depth.The polishing effect of bidirectional or along the grinding texture was better than that when the grinding direction was vertical to the texture.The depth of residue pollutants was not higher than 1 μm, which was close to that of glow argon ion bombardment method.Consequently, the easily pollution problem of titanium alloy sample was solved, and the calibration curves of carbon in LIBS analysis were improved.Simultaneously, the determination precision was enhanced.The analytical results of Ti-47.5Al-2.5V-1.0Cr titanium alloy were in good agreement with those obtained by other methods.
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