(1. 江蘇大學(xué) 材料科學(xué)與工程學(xué)院 江蘇省高端結(jié)構(gòu)材料重點實驗室，鎮(zhèn)江 212013；
2. Department of Materials Science and Engineering,
Norwegian University of Science and Technology, Trondheim 7491, Norway)
摘 要: 利用高分辨透射電鏡研究高壓扭轉(zhuǎn)大塑性變形納米結(jié)構(gòu)Al-Mg鋁合金中的位錯、層錯和形變孿晶。結(jié)果表明：在納米晶和超細(xì)晶內(nèi)均存在高密度的層錯和形變孿晶；形成層錯的Shockley部分位錯可分別由0°純螺型位錯和60°混合位錯分解得到；納米孿晶既可由晶內(nèi)層錯動態(tài)疊加而形成，也可由晶界向晶內(nèi)不斷發(fā)射部分位錯而向晶內(nèi)長大，從而分別實驗證實了分子動力學(xué)模擬預(yù)測的均質(zhì)和非均質(zhì)形核長大的孿生機制；觀察到了由4層層錯動態(tài)疊加而形成的特殊納米孿晶。此外，高分辨透射電鏡觀察表明：在不同滑移面上的層錯相交時，形成層錯而產(chǎn)生的拖曳部分位錯相遇可反應(yīng)生成壓桿位錯和Lomer-Cottrell位錯鎖。依據(jù)經(jīng)典位錯理論和晶界發(fā)射部分位錯的機制，提出了描述超細(xì)晶面心立方金屬和合金中層錯和形變孿晶形核長大的新模型。
關(guān)鍵字: 鋁合金；高壓扭轉(zhuǎn)；形變孿晶；層錯；位錯
（1. School of Materials Science and Engineering, Jiangsu Province Key Laboratory of High-end Structural Materials,
Jiangsu University, Zhenjiang 212013, China;
2. Department of Materials Science and Engineering,
Norwegian University of Science and Technology, Trondheim 7491, Norway）
Abstract:Dislocation, stacking faults (SFs) and deformation twins (DTs) in nanostructured Al-Mg alloys processed by high pressure torsion were identified using high-resolution transmission electron microscopy (HRTEM). The results show that SFs and DTs with high density exist within both nanocrystalline and ultrafine grains. SFs formed by Shockley partials can be dissociated from both 0° screw and 60° mixed dislocations. The homogeneous and heterogeneous twinning mechanisms previously predicted by molecular dynamics simulations were directly verified by HRTEM. A special four-layer twin formed by the dynamic overlapping of four SFs is experimentally observed. In addition, HRTEM observations suggest that stair-rod dislocations and Lomer-Cottrell locks form by the reactions of trailing partials of SFs meted on different slip planes. Based on the classical dislocation theory and the partial emission from grain boundaries, a new model to describe the nucleation and growth of SFs and DTs in ultrafine-grained FCC metals and alloys was proposed.
Key words: aluminum alloy; high pressure torsion; deformation twin; stacking fault; dislocation
