【作者】 孙文飞；

【导师】 梅显秀；

【作者基本信息】 大连理工大学 ， 等离子体物理， 2007， 硕士

【摘要】 用含Cⁿ⁺（30mol％）和H⁺（70mol％），加速电压为250kV，脉冲宽度为70ns的强流脉冲离子束（HIPIB）辐照DZ4镍基高温合金，通过对辐照前后各样品微观结构和宏观性能的分析，进一步认识HIPIB与材料表面作用的机制，以便了解HIPIB的应用范围。扫描电子显微镜（SEM）结果显示，辐照后样品的表面出现了熔坑，熔坑表面富集Cr、Mo、C等元素。熔坑是由于DZ4合金的物理化学性质不均匀，辐照时发生选择烧蚀造成的。多次辐照处理后，样品表面的熔坑边缘模糊了。透射电子显微镜（TEM）结果显示，原始样品主要是由γ′相和γ相组成的。与原始样品比较，辐照后的样品表面产生了一层厚度为10nm左右的纳米多晶层，它是由Ni、Cr、Al、Ti、W、Mo、Co等单质相组成的，晶粒尺度为5～10nm；在距表面一定深度范围内，不存在γ′相；随着深度的增加，γ′相的含量逐渐增加。在样品100-15距表面20μm的位置，存在一个位错密度很大的区域。X射线衍射（XRD）显示，辐照后的样品内部存在应力。动电位扫描阳极极化曲线分析显示，强流脉冲离子束辐照处理后DZ4合金的耐腐蚀性能明显提高，腐蚀速度下降，而且更容易达到钝化状态，维钝电流密度更小。恒温氧化实验表明，在高温氧化时，辐照后的样品更容易在表面形成一层连续致密的Al₂O₃保护性氧化物，使得DZ4合金的耐高温氧化性能有所改善。纳米硬度测试结果显示，辐照后样品最表面的硬度较大，随着深度的增加，达到硬度的极小值，然后硬度逐渐增加到基体的硬度值。正是由于硬度较大的表面层，导致辐照后样品表面的摩擦系数减小。辐照后样品截面的努氏显微硬度测试结果显示，HIPIB辐照提高了基体的硬度，从而提高了样品的耐磨损性能，这是由于HIPIB辐照使表面以下某些位置产生大量交织的位错，导致晶面的滑移阻力加大而造成的。更多还原

【Abstract】 Surface irradiation of refractory alloy DZ4 is realized by using High intensity pulsed ionbeam （HIPIB） containing Cⁿ⁺（30mol%） and H⁺（70mol%）, where the accelerating voltage andpulse duration are fixed at 250kV and 70ns respectively. The modification mechanism ofHIPIB irradiating on the surface of DZ4 alloy is studied by analyzing the microstructures andproperties of original and irradiated samples, in the purpose of further understanding theappropriate application fields of HIPIB method.Scanning electron microscopy （SEM） demonstrates that after radiations craters appear onthe surface of DZ4 alloy and there exist plenty of Cr, Mo, and C on the surface of the craters.The appearance of craters is due to uneven physical and chemical properties of materials.Craters trend to disappear after irradiated for many times. Transmission electron microscopy（TEM） demonstrates that the original sample is mostly composed ofγ’ andγ’ phases.Compared with the original sample, a 10nm-deep nanocrystal layer appears after irradiation,which is composed of Ni, Cr, Al, Ti, W, Mo and Co elemental crystal with a grain size of 5～10nm.γ’ does not exist under the nanocrystal layer, andγ’ content increases gradually to bethe same as the base with depth increasing. There exists a region with plenty of dislocations atthe position 20μm-deep under the surface of sample 100-15. X-ray diffraction （XRD）demonstrates that there exists stress in irradiated samples.The electrochemical corrosion test shows that the corrosion resistances of samples aregreatly improved after irradiated by HIPIB, corrosion rates decline, and passivations happenmore easily than the original one. The isothermal oxidation test shows that the hightemperature oxidation resistances of irradiated samples are also improved, because it’s mucheasier to form a continuous compact Al₂O₃ layer on the surface of irradiated samples than ofthe original one. Nanohardness test demonstrates that a maximum of hardness first appears onthe top surface of irradiated samples, and hardness decreases to a minimum one with thedepth increasing, and then finally increases to the same hardness value as the base. It is theharder irradiated surface layer that results in the decrease of the friction coefficients. Knoopmicrohardness （H_k） test also demonstrates that the hardness of the base is improved by HIPIBirradiation and the wear resistance is also improved accordingly, which can be attributed tothe appearance of a lot of dislocations.更多还原