钒微合金化对718合金中铌元素偏析行为的影响  

Effect of microalloying vanadium on micro-segregation behavior of niobium in 718 alloy

作　　者：莫燕[1] 王东哲[1,2,3] 蒋斌[4,5] 李永友[1] 刘海定[1] 王明波[1] 

机构地区：[1]重庆材料研究院有限公司,重庆400707 [2]耐腐蚀合金重庆市重点实验室,重庆400707 [3]国家仪表功能材料工程技术研究中心,重庆400707 [4]国家镁合金材料工程技术研究中心,重庆400044 [5]重庆大学材料科学与工程学院,重庆400044

出　　处：《金属热处理》2017年第4期37-41,共5页Heat Treatment of Metals

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)

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。The solidification structure of 0. 066% vanadium（ V）-containing 718 alloy ingot was studied by metallurgical microscope（ MM）,electron probe micro-analysis（ EPMA） and energy dispersive spectrum（ EDS）. The microstructure and precipitated phases characteristics of the two alloys were investigated,as well as distributions and micro-segregations of niobium（ Nb）. The results are as follows： refined dendritic structure,reduced second dendrite arm spacing and lower segregation coefficient of Nb are observed by the micro-alloying of V. Nb mainly distributes in Laves and carbide precipitated phases,quantitative characterization shows that volume fraction of the two phases can be greatly reduced in 718 alloy with V. The results of linear EPMA-EDS indicate that the further away from Laves phase,the lower Nb content,furthermore,V-containing sample displays slower decreasing trend. All results show that the alloying treatment of V improves microsegregation of Nb and refines dendritic structure of 718 alloy,which will benefit homogenization heat treatment and composition and microstructure homogeneousness. Particles of V-containing carbides become heterogeneous nucleation centers during solidification process,reduce the driving force of solidification nucleation,which make a narrower second dendrite arm spacing,a lower Laves phase and carbide volume fraction and a finer solidification structure.

关 键 词：铸锭 凝固组织 微观偏析 二次枝晶间距 LAVES相 铌 钒 

分 类 号：TG113.12[金属学及工艺—物理冶金]