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Trans. Nonferrous Met. Soc. China 22(2012) s370−s375 Effect of pre-deformation on microstructure and mechanical properties of 2219 aluminum alloy sheet by thermomechanical treatment AN Li-hui1,2, CAI Yang1, LIU Wei1, YUAN Shi-jian1, ZHU Shi-qiang2, MENG Fan-cheng2 1. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China; 2. Capital Aerospace Machinery Company, Beijing 100076, China Received 28 August 2012; accepted 25 October 2012 Abstract: Thermomechanical treatment is usually used to achieve good mechanical properties and microstructure of metal materials. The effect of pre-deformation on the microstructure and mechanical properties of 2219 aluminum alloy sheet by TMT process was investigated. The studies show that the yield strength and tensile strength increase firstly and decrease with the increase of pre-deformation under a certain heat treatment condition and total deformation. The tensile strength of 2219 aluminum alloy sheet reaches the maximum value when the pre-deformation is about 2%. It is also found that the very fine Al2Cu appears inside the grain, which is the precipitated phase for the strengthening of the 2219 aluminium alloy. Key words: 2219 aluminum alloy; thermomechanical treatment (TMT); pre-deformation; precipitation strengthening; mechanical properties 1 Introduction High performance aluminum alloy is widely used in the fields of aviation and aerospace to manufacture some main structures and key components of airplane or aircraft for its characteristics of low density and high strength. Generally, the high performance mechanical properties of this kind of aluminium alloy can be achieved by thermomechanical treatment (TMT) process, which includes three main procedures of solid solution-quenching, plastic deformation and aging [1]. TMT process can give the excellent performance of material by taking advantage of its deformation strengthening during plastic deformation and the transformation strengthening during heat treatment [2]. For example, TMT process can refine the precipitated phase significantly [3], and produce mesh substructure by the intertwined dislocation with precipitated phase, which can improve the mechanical properties of the 2014 aluminum alloy greatly [4]. Plastic deformation process may be useful in the effect of aging process, which is helpful to improve the mechanical properties of 2519A Foundation item: Project (NCET-11-0799) supported by the Program for New Century Excellent Talents in University of China; Project (HIT.BRETIII.201204) supported by Fundamental Research Funds for the Central Universities of China; Project (2011ZX04001-011) supported by the High-end CNC Machine Tools and Basic Manufacturing Equipment Technology Major Project Corresponding author: CAI Yang; Tel: +86-451-86414761; E-mail: 108caiyang@163.com DOI: 10.1016/S1003-6326(12)61733-6 aluminium alloy and refine the precipitated phase of alloys notably [5,6]. The mechanism of TMT process has been revealed by some studies that the plastic deformation in the phase of heat transition can increase the lattice defects, which has an great effect on the kinetics of the precipitated phase transition [7,8]. The typical lattice defects include dislocation, vacancy, stacking fault, small angle grain boundary, and high angle grain boundary, etc. So, as the results, plastic deformation can form greater area of dislocation networks, make the grain boundary distribution more uniform, microstructure and properties of aluminum alloy. What’s more, some studies also show that the pre-deformation before heat treatment is crucial for TMT process [9−14]. However, there are few study results available concerning the effect of the pre-deformation degree and the strengthening rule of pre-deformation on the phase transition and microstructure. Therefore, the effect of pre-deformation on microstructure and mechanical properties of 2219 aluminum alloy sheet in TMT process was investigated in this work. The flat rectangular blank was stretched at and achieve best