(1. 江蘇大學 材料科學與工程學院，鎮(zhèn)江 212013；
2. 上海交通大學 金屬基復合材料國家重點實驗室，上海 200240)
摘 要: 采用熔體直接反應法，以工業(yè)7055鋁合金為基體，利用K2TiF6和K2ZrF6多組元制備Al3(Ti0.5Zr0.5)原位顆粒強化鋁基復合材料，再將復合材料經過擠壓、固溶時效處理后進行深冷時效循環(huán)處理。采用正交實驗設計法研究降溫速度、處理時間和循環(huán)次數對復合材料顯微組織和力學性能的影響。采用差示熱分析儀對復合材料進行低溫熱分析，采用SEM和TEM對材料顯微組織進行觀察。結果表明：材料從液氮溫度77 K升溫至165 K左右時出現了明顯的放熱峰，此溫度處出現了相變。熱計算結果表明該溫度下大量析出了S相(Al2CuMg)。深冷處理后復合材料內部細小析出相數量增多，主要組分是η(MgZn2)相和η′(MgZn2′)相；隨著降溫速度、處理時間和循環(huán)次數增加，性質不穩(wěn)定且硬度高的η′相數量減少，性質穩(wěn)定硬度較低的η相數量增加。與未冷處理試樣相比，深冷時效循環(huán)處理后試樣的平均抗拉強度提高14.7%，沖擊韌性提高10.9%，伸長率提高50%，斷裂機制為韌窩型斷裂機制。當試樣具有高強度、高韌性時，對應的最優(yōu)冷處理參數為：降溫速度v為1 ℃/min、保溫時間t為24 h、循環(huán)次數N為1或2。當試樣的伸長率最高時，對應的參數為：v為10 ℃/min、t為36 h、N為1。復合材料強化機制為析出相強化、位錯強化和細晶強化等。
關鍵字: 鋁基原位復合材料；深冷時效循環(huán)處理；顯微組織；力學性能
（1. School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China;
2. The State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China）
Abstract:The in-situ Al3(Ti0.5Zr0.5) composite was synthesized using K2TiF6 and K2ZrF6 components in 7055 aluminum alloy by melt direct reaction method. Cryogenic aging circular treatment (CACT) was performed after extrusion deformation and solution-aging heat treatment. The effects of cooling rate (v), processing time (t) and circular index (N) on the microstructure and mechanical properties of composites were studied by orthogonal experimental method. The composite was studied by differential scanning calorimetry (DSC) under cryogenic condition, and the microstructure of composite was studied by SEM and TEM. The result shows that when the specimen is heated from the cryogenic temperature (77 K) to about 165 K, there will be an obvious exothermic peak. The phase transforms from matrix to S phase (Al2CuMg). There are amounts of fine precipitates in the composites, the main components are regarded as η (MgZn2) and η′(MgZn2′) phases. With increasing the v, t and N, the amount of η′ phase that is unstable but hard will decrease, while the stable but soft η phase will increase. Compared with the sample without CACT, the average tensile strength (σb), impact toughness (ak) and elongation (δ) of the sample with CACT have been enhanced by 14.7%,10.9% and 50%, respectively. The main fracture mechanism is dimple one. When the samples with high σb and ak are acquired, the optimal CACT parameters are: v=1 ℃/min; t=24 h and N=1 or 2. When the samples with superior elongation are acquired, the corresponding CACT parameters are: v=10 ℃/min, t=36 h and N=1. The strengthening mechanisms of CACT composite are precipitation strengthening, dislocation strengthening and fine crystalline strengthening.
Key words: in-situ aluminum matrix composite; cryogenic aging circular treatment; microstructure; mechanical property
