CuCoCrFeNi高熵合金激光焊接性研究

发布时间：2018-04-16 01:04

本文选题：高熵合金 + 激光焊接　；参考：《沈阳理工大学》2017年硕士论文

【摘要】：高熵合金具有高强度、高硬度、高耐磨性和耐蚀性等多种优异性能,激光焊接技术因其适用性广泛成为金属连接成型的重要手段,目前对于HEAs激光焊接性方面的研究还未有报道,因此,研究高熵合金激光焊接性对扩大其应用领域是非常有意义的。本文分别采用脉冲和光纤激光焊接对CuCoCrFeNi合金进行试验,研究发现其脉冲焊缝较光纤焊缝更容易出现裂纹。通过优化CuCoCrFeNi合金以及CuCoCrFeNi和AlCoCrFeNi异种合金光纤激光焊接工艺参数,对CuCoCrFeNi合金同种和异种接头的组织和性能进行分析与检测。试验结果表明,两种类型的接头均为高熵合金,同种接头为FCC相结构,异种接头为BCC相和有序A2相的混合结构。两种接头从熔合区到焊缝中心区,晶粒形态均是由柱状晶依次向胞状树枝晶和等轴晶转变,并且晶粒多在平行于001晶向上进行择优生长。同种接头焊缝区的Cu元素含量较其他元素含量低,异种接头焊缝区Al、Cu元素含量较其他元素含量低,但两种接头焊缝区内的各元素均能均衡分布,偏析明显减弱。异种接头焊缝区的硬度为210±30HV,稍高于同种接头焊缝区的硬度,两者均高于CuCoCrFeNi合金的硬度;此外,异种接头焊缝区的硬度远比AlCoCrFeNi合金的硬度低。同种接头的抗拉强度和屈服强度分别为421.3MPa和289.9MPa,延伸率为26.2%,断裂在母材处,断口形式为混合型断裂,断口形貌表明接头具有良好的力学性能。异种接头的抗拉强度为166MPa,断裂在AlCoCrFeNi合金侧,断口形式为解理断裂。在3.5%NaCl溶液中,同种接头发生点蚀和晶间腐蚀,其耐蚀性优越于CuCoCrFeNi合金。异种接头由于有裂纹存在,其耐蚀性较差,除有点蚀、晶间腐蚀外,还有缝隙腐蚀。
[Abstract]:High entropy alloys have many excellent properties, such as high strength, high hardness, high wear resistance and corrosion resistance. Laser welding technology has become an important means of metal bonding because of its applicability.At present, the research on HEAs laser weldability has not been reported. Therefore, it is very significant to study the laser weldability of high entropy alloy to expand its application field.In this paper, pulse and fiber laser welding are used to test the CuCoCrFeNi alloy, and it is found that the pulsed weld is more prone to crack than the optical fiber weld.By optimizing the parameters of CuCoCrFeNi alloy, CuCoCrFeNi and AlCoCrFeNi dissimilar alloy optical fiber laser welding process parameters, the microstructure and properties of the same and dissimilar joint of CuCoCrFeNi alloy were analyzed and tested.The results show that the two types of joints are high entropy alloy, the same type joints are FCC phase structure, and the dissimilar joints are mixed structure of BCC phase and ordered A2 phase.From the fusion zone to the center of the weld, the grain morphology of the two kinds of joints is changed from columnar crystal to cellular dendrite and equiaxed crystal, and the grain grows preferentially in parallel to 001 crystal.The content of Cu in the weld zone of the same kind of joint is lower than that in the other elements, and the content of Cu in the weld zone of the dissimilar joint is lower than that of the other elements. However, all the elements in the weld zone of the two kinds of joints can be evenly distributed and the segregation is obviously weakened.The hardness of weld zone of dissimilar joint is 210 卤30HVwhich is slightly higher than that of the same kind of joint, both of which are higher than that of CuCoCrFeNi alloy, in addition, the hardness of weld zone of dissimilar joint is much lower than that of AlCoCrFeNi alloy.The tensile strength and yield strength of the same joint are 421.3MPa and 289.9MPa, respectively, and the elongation is 26.2. The fracture is at the base metal and the fracture is a mixed fracture. The fracture morphology shows that the joint has good mechanical properties.The tensile strength of the dissimilar joint is 166 MPA, the fracture is on the side of AlCoCrFeNi alloy and the fracture is cleavage fracture.In 3.5%NaCl solution, pitting corrosion and intergranular corrosion occur in the same joint, and the corrosion resistance of the same joint is superior to that of CuCoCrFeNi alloy.The corrosion resistance of dissimilar joints is poor due to the existence of cracks. Besides a bit of corrosion and intergranular corrosion, there is gap corrosion.
【学位授予单位】：沈阳理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG456.7

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