摘要
利用光镜、扫描电镜和能谱仪等手段分析了不同Nb元素含量的GH4169合金钢锭组织特点及元素偏析规律,并对经单阶段均匀化热处理后钢锭的组织及残留析出相特征进行分析。结果表明:随着Nb元素含量增加,GH4169合金铸锭由边缘到心部,枝晶组织粗化,二次枝晶间距增大,Nb、Ti元素的偏析系数亦增大;经1160℃保温20h的均匀化处理后,Nb添加量越多,未回溶的析出相残留越多,且残留析出相有很明显的聚集趋势,残留析出物聚合体主要为富Nb的Laves相及富Nb、Ti元素的碳化物。不同Nb元素含量钢锭中Laves相完全回溶需要的时间应不相同,在高Nb含量条件下,传统的均匀化工艺无法使Laves相完全回溶;若同时考虑钢锭的尺寸因素,高Nb含量条件下,残留析出相的聚合体可能会演化为"黑斑"缺陷而使钢锭报废。
The microstructure characteristics and micro-segregation evolution for GH4169 alloy ingots with different Nb content were studied by OM, SEM and EDS. The properties of retained precipitates for single-stage homogenized ingots were investigated. The results are as follows： with the increase of Nb content, the dendrites get coarsening and the secondary dendrite space and the segregation coefficient of Nb and Ti elements are both increasing from the edge to the center for all ingots at radial direction. For as-homogenized ingots, the volume fraction of retained precipitates, mainly consist of Nb-riched Laves phase and Ti-riched carbides, increases with the increase of Nb content. The absolute dissolving time is different for each batch of GH4169 alloy ingots with different Nb content, or the traditional homogenization process can not satisfy all GH4169 alloy ingots, otherwise, if the size of ingots or Nb element content are over a critical value, the defect of freckle consisting of the retained precipitates may form, leading to the waste ingots of GH4169 alloy. The homogenizing parameters for GH4169 alloy ingots must be determined by actual high content of Nb element.
出处
《热加工工艺》
CSCD
北大核心
2013年第10期45-49,共5页
Hot Working Technology
基金
国家自然科学基金资助项目(50974144)
