一种典型低密度镍基单晶高温合金的制备与组织性能研究

发布时间：2018-02-12 09:50

  本文关键词： 镍基单晶高温合金 低密度 微观组织 力学行为　出处：《沈阳大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文设计了一种低密度镍基单晶高温合金,采用螺旋选晶法制备了[001]取向镍基单晶试棒,利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、差示扫描热分析(DSC)等研究了镍基单晶合金铸态与热处理态组织、典型条件下瞬时拉伸性能和高温低应力蠕变性能。对合金的铸态组织研究发现,合金中共晶含量约为0.7vol%,一次枝晶间距约为265mm,略低于典型的第二代单晶高温合金;采用排水法测量合金的密度为8.2g/cm3,显著低于典型二代单晶;采用DSC法和金相法测定了合金的初熔温度,并通过不同时间的固溶处理确定了合金的固溶时间,最终制定了合理的热处理制度:1350℃/1h+1360℃/5h+空冷→1080℃/5h+空冷→900℃/8h+空冷。研究了合金完全热处理后γ和γ'两相微观组织,结果表明,合金完全热处理后,γ'相的平均尺寸约为0.3mm,体积分数为65vol%,γ基体宽度约为45nm;SEM和TEM观察表明合金基体并未宽化也没有二次γ'相析出。研究了合金在室温、中温和高温三个典型温度下的拉伸行为,结果表明,合金在室温和中温(760℃)拉伸时应力应变曲线上出现锯齿流变现象(PLC效应),曲线上的锯齿波主要为C型波;对合金在不同温度下拉伸断口分析表明,室温为典型的解理断裂,中温(760℃)为纯剪切断裂,高温(1100℃)为微孔聚集型断裂;同时对合金在典型高温低应力蠕变条件下的蠕变行为研究表明,合金蠕变断裂后γ'相发生筏化,在1050℃/200MPa和1100℃/137MPa条件下筏化γ'相厚度分别为0.7mm和1mm;合金在上述两种条件下均出现拓扑倒置现象,其NA(γ')值分别为-0.04mm-2和-0.06mm-2;合金蠕变断裂模式均为微孔聚集型断裂。
[Abstract]:In this paper, a low density nickel base single crystal superalloy was designed. [001] oriented nickel base single crystal test rod was prepared by spiral crystal selection method. The as-cast and heat-treated microstructure of Ni-base single crystal alloy was studied by optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM) and differential scanning calorimetry (DSC). Under typical conditions, the transient tensile properties and creep properties at high temperature and low stress were studied. It was found that the eutectic content of the alloy was about 0.7 voll, and the primary dendrite spacing was about 265 mm, which was slightly lower than that of the typical second generation single crystal superalloy. The density of the alloy measured by drainage method is 8.2 g / cm 3, which is significantly lower than that of the typical second generation single crystal, the initial melting temperature of the alloy is measured by DSC and metallography, and the solution time of the alloy is determined by solution treatment at different time. Finally, a reasonable heat treatment system was worked out: 1: 1350 鈩，

本文编号：1505350