铜与高熵合金电子束焊接接头微观组织与接头性能研究

发布时间：2018-06-27 13:28

本文选题：电子束焊 + CoCrFeMnNi　；参考：《兰州理工大学》2017年硕士论文

【摘要】：伴随工业技术的进步,铜与钢的异种结构件得到了广泛的应用,但是Cu与Fe在固态时的互溶度很小,不论采用何种焊接方法,对Cu/钢的直接焊接,会不可避免的产生液相分离或者焊接缺陷,这些因素对接头的力学性能有很大的影响。近年来,研究者发现了一种具有众多优良性能的新体系的合金-高熵合金。更重要的是,由于其具有高的混合熵,高熵合金对新组元有一定的固溶度,在一定范围内可以形成简单的FCC或者BCC结构。本课题将高熵合金CoCrFeMnNi作为焊接材料,研究该合金与Cu的电子束焊接接头。首先,研究分析了不同Cu含量对CoCrFeMnNi Cux(x=0,0.2,0.4,0.6,0.8,1,1.2)高熵合金的微观组织及力学性能的影响。结果表明:不同Cu含量的CoCrFeMnNi Cux高熵合金组织都为简单的FCC型固溶体结构。该体系高熵合金具有良好的塑性。压缩实验后,所有的合金柱变为鼓状,没有发生断裂。这为Cu/CoCrFeMnNi高熵合金电子束焊接提供了依据。进而研究了偏束距离、焊接速度对Cu/CoCrFeMnNi高熵合金电子束焊接接头的微观组织和结合强度的影响。主要研究结果如下:(1)偏束距离影响着焊缝熔池的融合比。随着电子束由铜侧偏向高熵合金侧,焊缝熔池的高熵合金的贡献量增加,铜的贡献量减少。当偏束距离为-mm2.0及mm0时,高熵合金侧出现了铜的渗透裂纹。这是因为铜对熔池的贡献量较多,高熵合金界面处会有富铜相的存在。在焊接过程产生复杂内应力的作用下,富铜相会从高熵合金侧的焊缝界面沿着高熵合金的晶界向高熵合金母材渗透。不同偏束距离下,高熵合金侧的组织为典型的柱状晶,而铜侧存在一个铜的过渡区。熔池中铜的含量对焊缝区的组织形貌有很大影响。所有焊接接头焊缝区的组织都为FCC型固溶体相。拉伸后接头在铜侧发生断裂。当偏束距离0.6mm时,接头抗拉强度达到最大值225MPa。偏束距离对抗拉强度的影响较小,但对应变的影响较大,这与铜侧软化有关。所有接头焊缝区的显微硬度变化平缓,没有出现明显的突变。(2)焊接速度控制着焊接热输入。焊接速度较大,电子束作用于母材的时间短,热输入较小,底部出现未焊透缺陷;焊接速度较小,电子束作用于母材的时间长,热输入大,底部焊透,但是上部焊缝区的缺损严重。不同焊接速度下,焊接接头的组织分布极不均匀,但是铜对熔池的贡献量少,靠近高熵合金侧焊缝区一定距离Cu的含量很少。高熵合金侧的晶粒为柱状晶,铜侧出现了富铜的过渡区,这是高熵合金的迟滞扩散效应导致的。焊缝区的晶粒为柱状晶。平均晶粒尺寸的大小受焊接速度的影响。拉伸实验后,焊接速度为1200mm/min时,底部出现未焊透缺陷,断裂发生在上部焊缝区。焊接速度为800mm/min和1000mm/min时,断裂发生于铜侧。在800mm/min时,热输入大,导致铜侧发生软化,应变相对较小。但是焊接速度对抗拉强度的影响很小。不同焊接速度下焊缝区的硬度值分布平缓,硬度值没有出现大幅度增加。焊缝区硬度与高熵合金的硬度近似相等。
[Abstract]:With the progress of industrial technology, the dissimilar structure parts of copper and steel have been widely used, but the mutual solubility of Cu and Fe in solid state is very small. No matter which welding method, the direct welding of Cu/ steel will inevitably produce liquid phase separation or welding defects. These factors have a great influence on the mechanical properties of the joint in recent years. The researchers found a kind of alloy high entropy alloy with many excellent properties, and more importantly, because of its high entropy, high entropy alloy has a certain solid solubility to the new component, and can form a simple FCC or BCC structure in a certain range. This topic studies the high entropy alloy CoCrFeMnNi as a welding material. The effect of different Cu content on the microstructure and mechanical properties of CoCrFeMnNi Cux (x=0,0.2,0.4,0.6,0.8,1,1.2) high entropy alloy is investigated and analyzed. The results show that the structure of CoCrFeMnNi Cux high entropy alloy with different Cu content is simple FCC solid solution structure. The high entropy alloy of this system is good. Good plasticity. After the compression test, all the alloy columns become drums and no breakage. This provides a basis for Cu/CoCrFeMnNi high entropy alloy electron beam welding. Then the effect of beam deviation and welding speed on the microstructure and bonding strength of Cu/CoCrFeMnNi high entropy alloy electron beam welded joint is investigated. The main results are as follows: (1) When the electron beam deviated from the copper side to the high entropy alloy side, the contribution of the high entropy alloy to the weld pool increased and the contribution of the copper decreased. When the beam distance was -mm2.0 and mm0, the high entropy alloy side appeared the copper permeation crack. This is because copper has more contribution to the molten pool and the high entropy alloy interface. Under the action of complex internal stress in the welding process, the rich copper phase will permeate the high entropy alloy interface along the grain boundary of high entropy alloy along the grain boundary of the high entropy alloy. Under the different beam distance, the microstructure of the high entropy alloy side is a typical columnar crystal, while the copper side has a copper transition zone. Copper in the molten pool. The structure of the weld zone has a great influence on the microstructure of the weld zone. The microstructure of all welded joints is FCC type solid solution. The joint is broken at the copper side after stretching. When the beam distance is 0.6mm, the tensile strength of the joint is up to the maximum value 225MPa., but the effect on the tensile strength is little, but it has great influence on the strain, which is soft to the copper side. The microhardness changes of all joint weld zones are slow, no obvious mutation is found. (2) welding speed controls welding heat input. The welding speed is high, the time of welding is large, the time of the electron beam on the base material is short, the heat input is small, the bottom is not penetrated, the welding speed is small, the time of the electron beam on the base material is long, the heat input is big, bottom. The defects in the upper weld zone are serious, but the defects in the upper weld zone are serious. The microstructure distribution of the welded joint is very uneven at different welding speeds, but the contribution of copper to the molten pool is less, and the content of Cu near the high entropy alloy side welds is few. The grain of the high entropy alloy side is columnar crystal and the copper rich transition zone appears on the copper side. This is a late high entropy alloy. The grain size of the weld zone is columnar crystal. The size of the average grain size is affected by the welding speed. When the welding speed is 1200mm/min, there is no penetration defect at the bottom. The fracture occurs in the upper weld zone. When the welding speed is 800mm/min and 1000mm/min, the fracture occurs on the copper side. At 800mm/min, the heat transfer. The strength of the copper side is softened and the strain is relatively small, but the influence of the welding speed on the tensile strength is small. The hardness distribution of the weld zone is slow and the hardness value does not increase substantially. The hardness of the weld zone is approximately equal to the hardness of the high entropy alloy.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG407

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