钒微合金化对718合金中铌元素偏析行为的影响

发布时间：2018-05-20 10:02

本文选题：铸锭 + 凝固组织　；参考：《金属热处理》2017年04期

【摘要】：利用金相显微镜、电子探针、能谱仪等分析了含钒元素(V)0.066%的718合金铸锭凝固组织,对其微观组织和析出相特征进行分析,研究其中易偏析铌元素(Nb)的分布状态及偏析规律。结果表明,V元素的微合金化使718合金铸锭枝晶组织得到细化,二次枝晶间距及Nb元素的偏析系数均有所降低;由于Nb元素主要分布在Laves相及碳化物中,通过对二者体积分数的定量表征,V元素的加入大大降低Laves相及碳化物的析出,体积分数降低;线扫描分析表明,距Laves相越远,Nb元素含量越低,而含V样品中,这种含量降低的趋势有所减缓。所有分析结果均表明,V元素的合金化改善了718合金中Nb元素的偏析状态,细化了枝晶组织,对降低718合金均匀化热处理难度、提高合金成分和组织均匀性有利。含V碳化物在凝固过程中成为异质形核点,减小了凝固形核的驱动力,使得二次枝晶间距变小,表现出更小的Laves相体积分数和较细的枝晶组织。
[Abstract]:The solidification microstructure of 718 alloy ingot containing V ~ (0.066%) was analyzed by means of metallographic microscope, electron probe and energy spectrometer. The microstructure and precipitation phase characteristics of 718 alloy ingot were analyzed, and the distribution and segregation law of niobium (NB) were studied. The results show that the dendrite structure of 718 alloy ingot is refined by microalloying, and the secondary dendrite spacing and segregation coefficient of NB element decrease, because NB is mainly distributed in Laves phase and carbides. The volume fraction of Laves phase and carbides was decreased by the addition of V element, and the linear scanning analysis showed that the farther away from the Laves phase, the lower the content of NB element, and the lower the content of NB element in the V sample, and the lower the content of NB element in the sample containing V, the further away from the Laves phase, the lower the content of NB element was. The decreasing trend of this content has slowed down. All the results show that alloying of V element can improve the segregation state of NB element in 718 alloy, refine the dendrite structure, reduce the difficulty of homogenization heat treatment of 718 alloy, and improve the composition and microstructure homogeneity of 718 alloy. V-containing carbides become heterogeneous nucleation points during solidification, which reduces the driving force of solidification nucleation and makes secondary dendritic spacing smaller, showing smaller volume fraction of Laves phase and finer dendritic structure.
【作者单位】：重庆材料研究院有限公司;耐腐蚀合金重庆市重点实验室;国家仪表功能材料工程技术研究中心;国家镁合金材料工程技术研究中心;重庆大学材料科学与工程学院;
【基金】：中国博士后科学基金(2014M560701) 重庆市博士后科学基金(Xm2014042) 重庆市科技创新领军人才支持计划(CSTCKJCXLJRC01) 重庆市基础科学与前沿技术研究专项项目(cstc2016jcyj A0165)
【分类号】：TG132.3;TG244.3

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