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時效制度對2A97鋁鋰合金強韌性的影響
發布人：上海艾荔艾金屬材料有限公司www.jshcn.cn
更新時間：2015-11-03
通過拉伸試驗及平面應變斷裂韌性測試，研究不同時效制度對2A97合金強韌性的影響，并利用透射電鏡和掃描電鏡對合金的微觀組織及斷口形貌進行觀察。
時效制度對2A97鋁鋰合金強韌性的影響Effects of aging treatment on strength and?fracture toughness of 2A97 aluminum-lithium alloy
通過拉伸試驗及平面應變斷裂韌性測試，研究不同時效制度對2A97合金強韌性的影響，并利用透射電鏡和掃描電鏡對合金的微觀組織及斷口形貌進行觀察。結果表明：2A97合金在135 ℃單級時效時斷裂韌性較好，但強度偏低；雙級時效可促進強度的提高,但第二級時效溫度過高時(175 ℃)，斷裂韌性迅速下降，經過(135 ℃, 36 h)+(150 ℃, 18 h)時效，可得到較好的強韌性匹配，其σb、σ0.2和KIC?分別為547 MPa、489 MPa和28.9 MPa·m1/2。2A97合金中的主要強化相為δ ′相和T1相。δ ′相易共面滑移而引起應力集中，對合金韌性不利；T1相能有效地阻止位錯滑移,對合金強度有顯著提高。2A97合金在時效初期以穿晶和沿晶混合型斷裂為主，斷口表現出明顯的分層特征，具有較好的韌性；隨時效時間的延長，析出相的體積分數、尺寸以及臨界分切應力增大，所造成的應力集中更明顯，同時晶界平衡相增多，晶界無沉淀帶加寬，沿晶斷裂比例增多，合金韌性急劇下降。
The effect of ageing treatment on the strength and fracture toughness of 2A97 alloy was investigated by tensile test and plane-strain fracture toughness experiments. The microstructures and fracture morphologies were observed and analyzed by TEM and SEM. The results indicate that the 2A97 alloy obtains a preferable fracture toughness of in single aging at 135 ℃，but its strength is relatively low. The duplex aging enhances the strength, while the fracture toughness deteriorates at an excessive temperature as 175 ℃. The 2A97 alloy can obtain the superior combination of the strength and toughness after (135 ℃, 36 h)+(150 ℃, 18 h) aging treatment, with the σb, σ0.2and KIC?of 547 MPa, 489 MPa and 28.9 MPa·m1/2, respectively. The δ′ and T1?phases are the major precipitates in the 2A97 alloy. The δ′ phase may induce the stress localization and thus deteriorate the toughness, while the T1phase can resist the slip of dislocation effectively and significantly enhance the strength. At the early stage, it primarily presents a hybrid of transgranular and intergranular fractures with obvious delamination crackings at the fracture surfaces, which indicates a high level of toughness. The volume fraction, size and critical resolved shear stress of precipitations increase with prolonging the aging time, and lead to more severe stress localizations. In additions, the more equilibrium phases at grain boundaries, the wider PFZs together with the greater proportional of intergranular fractures result in a sharply reduce of fracture toughness.
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