铸态DD5单晶在热处理过程中的组织转变规律

Microstructure Transformation Rule of As-cast DD5 Single Crystal during Heat Treatment

目的对DD5单晶组织进行热处理制度,分析在热处理各阶段下DD5单晶组织尺寸及转变的规律。方法采用热处理制度,对铸态DD5镍基单晶高温合金分别进行固溶(1300℃,保温2 h,空冷)、一次时效(1120℃,保温4 h,空冷)、二次时效(1080℃,保温4 h,空冷)热处理工艺,对比分析各热处理工艺下DD5单晶的组织特征,研究热处理制度下DD5单晶组织转变的规律。结果在固溶和时效处理下,DD5单晶显微组织呈十字形枝晶样貌,组织中的γ′相有一定程度的长大,枝干和枝间的形态、尺寸逐步接近,最后γ′相形貌演变为规则立方状。结论随着各个阶段热处理制度的逐步完成,γ′相的有序性和立方度逐步提高,并与基体相γ保持高度共格关系,γ+γ′共晶组织和枝晶间析出的粗大γ′相逐渐扩散溶解。

The paper aims to study the heat treatment system of DD5 single crystal structure,and to analyze the size and transformation rule of DD5 single crystal structure in different stages of heat treatment.The heat treatment system was applied to make as-cast DD5 nickel base single crystal superalloy go through solid solution(1300℃,2 h insulation,air cooling),primary aging(1120℃,heat preservation,4 h,air cooling)and secondary aging(1080℃,heat preservation,4 h,air cooling),to compare and analyze the characteristics of the DD5 single crystal under different heat treatment processes and the transformation rules of DD5 single crystal structure in the heat treatment system.Under the solid solution and aging treatment,the microstructures of DD5 single crystal showed the appearance of cruciform dendrites,theγ′phase in the tissue grew up to a certain extent,the morphology and size of branches and inter-branches were gradually close,and the morphology ofγ′phase evolved into regular cubic shape.With the gradual completion of various stages of heat treatment system,the sequence and cubic degree ofγ′phase are gradually increased in a high coherency relation with matrix phaseγandγ+γ′eutectic tissue and the coarseγ′phase precipitated between dendrites are gradually diffused and dissolved.