A hidden precipitation scenario of theθ’-phase in Al-Cu alloys  

作　　者：L.Zhou C.L.Wu P.Xie F.J.Niu W.Q.Ming K.Du J.H.Chen 

机构地区：[1]center for high-resolution electron microscopy,college of materials science and engineering,hunan university,changsha,hunan,410082,china [2]shenyang national laboratory for materials science,institute of metal research,chinese academy of sciences.shenyan7.110016,china

出　　处：《Journal of Materials Science & Technology》2021年第16期126-138,共13页材料科学技术（英文版）

基　　金：the National Natural Science Foundation of China(Nos.51831004,51801060,51671082,11427806,51471067);the National Key Research and Development Program of China(No.2016YFB0300801)。

摘　　要：Al-Cu binary alloys are important and interesting industry materials.Up to date,the formation mechanisms of the key strengthening precipitates,namedθ’-phase,in the alloys are still controversial.Here,we report that for non-deformed bulk Al-Cu alloys theθ’-phase actually has its own direct precursors that can form only at elevated aging temperature(>ca.200℃).These high-temperature precursors have the same plate-like morphology as theθ’-phase precipitates but rather different structures.Atomicresolution imaging reveals that they have a tetragonal structure with a=0.405 nm and c=1.213 nm,and an average composition of Al_(5-x)Cu_(1+x)(0≤x<1),being fully coherent with the Al-lattice.This precursor phase may initiate with a composition of Al5 Cu and evolve locally towards Al_(4)Cu_(2)in composition,eventually leading to a consequent structural transformation into theθ’-phase(Al4 Cu2=Al2 Cu).There are evidences that because of their genetic links in structure,such a high-temperature precursor may transform to theθ’-phase without having to change their morphology and interface structure.Our study reveals a well-defined and previously hidden precipitation scenario for theθ’-phase to form in Al-Cu alloys at an elevated aging temperature.

关 键 词：AlCu alloy AGE-HARDENING PRECIPITATION Electron microscopy 

分 类 号：TG146.21[一般工业技术—材料科学与工程]