【作者】 黎阿男；

【导师】 田素贵； 尚丽娟；

【作者基本信息】 沈阳工业大学 ， 材料物理与化学， 2011， 硕士

【摘要】 本文采用Nv法和Md法对不同W含量镍基合金进行成分设计及TCP相的析出倾向预测；通过合金制备及长期时效处理,研究了元素W含量对合金TCP相析出倾向的影响；通过对不同合金进行蠕变性能测试和组织形貌观察,研究了W含量对镍基单晶合金组织稳定性及蠕变性能的影响。结果表明,在Md、Nv最大值分别为0.9836和2.210的系列合金成分中,无TCP相析出。随元素W含量提高,经1080℃时效300h,合金中γ’相仍保持立方体形态,具有较好的组织稳定性;与7.5%W单晶合金相比,9%W合金具有较好的蠕变抗力,在实验的温度和应力范围内,该合金在稳态期间的蠕变激活能为Q=465kJ/mol。在高温蠕变初期,合金中γ’相已转变成N-型筏状结构,在稳态蠕变期间合金的变形机制是位错攀移越过筏状Y’相,其中,筏状γ’相与应力轴垂直可有效阻碍位错运动是使合金具有较好蠕变抗力的主要原因。在蠕变断裂样品的不同区域,筏状γ’相具有不同的形貌,在远离断口区域,筏状γ’相与应力轴方向垂直,近断口区域筏状γ’相尺寸及扭曲程度增加的原因是γ’相承受的应力及变形程度增大所致。中温高应力蠕变期间,合金中γ’相不形成筏状组织,其变形机制是<110>超位错剪切立方γ’相,其中,切入γ’相内的<110>超位错可发生分解,形成(1/3)<112>不全位错+层错的位错组态,该位错组态可抑制位错的交滑移,提高合金的蠕变抗力；而合金在高温蠕变后期的变形机制是<110>超位错剪切筏状γ’相。提高固溶温度可降低合金在枝晶臂/间的成分偏析,改善均匀化程度及蠕变寿命。随W含量提高,可有效提高合金的高温蠕变抗力；而合金中存在组织缺陷,可明显降低合金的蠕变寿命。更多还原

【Abstract】 By means of Md and Nv methods, nickel-base superalloys with different tungsten content have been designed to predict the precipitated tendency of TCP phase. The influence of tungsten content on the precipitated tendency of TCP phase is investigagted by means of the preparing alloys and long term aging treatment. And the effects of the element W content on the microstructure stability and creep properties of the single crystal nickel-base superalloys are investigated by means of the measuring creep properties and microstructure observation.Results show that no TCP phase is precipitated when the maximum of Md and Nv values were calculated to be 0.9836 and 2.210, respectively, in the composition designed of the alloys. After aged for 300 h at 1080℃, theγ’ phase in the alloy still remains the cubical configuration with the increase of the element W content, therefore, the alloy displays a better microstructure stability. Compared to the alloy with 7.5% W,9%W alloy has a better creep resistance, in the ranges of the applied stress and temperature, the activation energy of the alloy during steady state creep is calculated to be Q= 465kJ/mol. In the initiation period of high temperature creep, theγ’ phase in the alloy is transformed into the N-type rafted structure, and the deformation mechanism of the alloy during steady state creep is that dislocation climbs over the raft-likeγ’ phase, thereinto, the raftedγ’ phase which is perpendicular to the applied stress axis may effectively hinder the dislocation movement, which is thought to be the main reason of the alloy possessing the better creep resistance. The various morphology of the raftedγ’ phase is displayed in the different regions of the creep samples, the raftedγ’ phase which is vertical to the applied stress axis appears in the region far from the fracture, and the twisted raftedγ’ phase appears in the region near the fracture, which is attributed to the servere plastic deformation occurred in the region. During middle temperature creep, no rafted of theγ’ phase is detected in the alloy, and the deformation mechanism in the alloy is that the cubicalγ’ phase is sheared by the<110> super-dislocation which may be decomposed into the the configuration of (1/3)<112> partials+stacking faults, which may hinder the cross-slipping of the dislocations to improve the creep resistance of the alloy. And the deformation mechanism of the alloy in the later stage of creep at high temperature is that<110> super dislocation shears into the raftedγ’ phase. The uniformity composition and creep lifetimes of the alloy may be improved by enhancing the solution temperature to decrease the segregation in the dendrite /interdendric regions. The creep resistance of the alloy at high temperature may be enhanced with the increase of the element W content. And the microstructure defection may obviously deteriorate the creep properties of the alloy.更多还原