(1. 江蘇大學(xué) 材料科學(xué)與工程學(xué)院，鎮(zhèn)江 212013；
2. 吉林大學(xué) 超硬材料國家重點實驗室，長春 130012)
摘 要: 為了考察低地球軌道衛(wèi)星運行環(huán)境下金屬材料的冷熱疲勞損傷機制，采用模擬實驗，并利用光學(xué)顯微鏡、XRD、TEM 及顯微硬度儀分析研究熱循環(huán)作用下2A12鋁合金的微觀結(jié)構(gòu)和性能的演化行為。結(jié)果表明: 在200次以內(nèi)的熱循環(huán)過程中，樣品硬度有所降低；200~300次循環(huán)樣品則出現(xiàn)循環(huán)硬化現(xiàn)象；300次循環(huán)后，樣品硬度迅速下降，出現(xiàn)循環(huán)軟化現(xiàn)象。微結(jié)構(gòu)分析結(jié)果表明：熱循環(huán)過程中，2A12鋁合金的性能變化與其微觀結(jié)構(gòu)的演化行為關(guān)系密切，300次熱循環(huán)時，樣品中形成了大量尺寸細小的針狀S′相(Al2CuMg)；而500次循環(huán)樣品中，S′相消失，代之以粗大S相(Al2CuMg)的形成。此外，500次熱循環(huán)后，析出相附近區(qū)域形成大量的空穴，這些空穴容易成為冷熱疲勞裂紋萌生的有利位置。
關(guān)鍵字: 熱循環(huán)；2A12鋁合金；微觀結(jié)構(gòu)；疲勞損傷
（1. School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China;
2. State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China）
Abstract:The fatigue damage mechanisms of metal material under the satellite operation condition of low earth orbit environment were investigated. Optical microscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and microhardness tester were used to investigate the evolution behavior of microstructures and properties of 2A12 aluminum alloy under various thermal cycles. The results indicate that the hardness decreases a little within 200 cycles, and the cyclic hardening phenomenon appears in the 200-300 cycles. After 300 cycles, the hardness of sample decreases evidently, the cyclic softening phenomenon turns up. The changes of performances of 2A12 aluminum alloy during the thermocycling process are closely related to the microstructural evolution. There are a lot of needle-like S′ phases (Al2CuMg) with small sizes in the samples after 300 thermal cycles. Up to 500 cycles, the S′ phases disappear, and bulky S phases (Al2CuMg) form. In addition, a large number of the cavities appear near the precipitates. The cavities are likely to become the favorable positions for the initiation of fatigue cracks.
Key words: thermocycling; 2A12 aluminum alloy; microstructure; fatigue damage
