(1. 貴州工程應(yīng)用技術(shù)學(xué)院 機(jī)械學(xué)院，畢節(jié) 551700；
2. 沈陽工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，沈陽 110870；
3. 中航工業(yè)北京航空材料研究院，材料檢測與評(píng)價(jià)航空科技重點(diǎn)實(shí)驗(yàn)室，北京 100095)
摘 要: 通過不同工藝熱處理、蠕變性能測試及組織形貌觀察，研究了固溶溫度對(duì)一種定向凝固鎳基合金中碳化物形態(tài)演化與蠕變性能的影響。結(jié)果表明：鑄態(tài)DZ125合金中存有粗大塊狀MC型碳化物，熱處理期間合金中MC型碳化物可發(fā)生分解和形態(tài)演化，逐步轉(zhuǎn)變成粒狀M23C6型碳化物。隨固溶溫度提高、時(shí)間延長，碳化物發(fā)生分解及形態(tài)演化的幾率增加，并使細(xì)小粒狀M23C6型碳化物沿晶界不連續(xù)析出。與低溫固溶處理合金相比，高溫固溶處理合金在780 ℃具有良好的蠕變抗力。其中，以共格方式嵌鑲在g 基體中的立方γ′相均勻分布在枝晶干和枝晶間區(qū)域，并有細(xì)小粒狀碳化物沿晶界彌散析出，可抑制晶界滑移，是大幅度提高合金蠕變抗力的主要原因。在近780 ℃蠕變后期，與應(yīng)力軸呈45°角的晶界承受較大的剪切應(yīng)力。裂紋在沿與應(yīng)力軸呈45°角的晶界處萌生與擴(kuò)展，直至斷裂是合金的蠕變斷裂機(jī)制。
關(guān)鍵字: 鎳基合金；固溶溫度；碳化物；形態(tài)；蠕變；裂紋萌生與擴(kuò)展
（1. School of Mechanical Engineering, Guizhou University of Engineering Science, Bijie 551700, China;
2. School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178, China;
3. Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation, AVIC Beijing Institute of Aeronautical Materials, Beijing 100095, China）
Abstract:By means of heat treatment at different regimes, creep properties measurements and microstructure observations, an investigation has been made into the influence of solution temperature on the carbides configuration evolution and creep properties of a directionally solidified nickel-based superalloy. The results show that the thicker bulk-like MC-type carbide is distributed in the as-cast DZ125 superalloy. And the decomposition and configuration evolution of the MC-type carbide occur gradually, during heat treatment, to transform into the particle-like M23C6-type carbides. As the solution temperature enhances and time prolongs, the probability of the MC-type carbide occurring decomposition and morphology evolution increase, which may promote significant amount of particle-like M23C6-type carbide precipitating along the grain boundary of alloy. Compared with the alloy solution treated by lower temperature, the alloy solution treated at higher temperature displays a better creep resistance at a temperature near 780 ℃. Wherein, the fine γ′ precipitates embedded coherent in the matrix phase are homogeneously distributed in the dendrite/ inter-dendrite regions, and some M23C6-type carbide particles along the grain boundaries may restrain the slipping of boundary, which is thought to be the main reasons of alloy having better creep resistance. At the latter stage of creep at a temperature near 780 ℃, the bigger shearing stress applying in the boundaries at about 45° angles relative to the stress axis results in the initiation and propagation of the micro-cracks along the ones up to fracture, which is thought to be fracture mechanism of the alloy during creep.
Key words: directional solidification nickel-based alloy; solution temperature; microstructure; carbide; creep; initiation and propagation of crack
