中文摘要：

为了提高7075铝合金的力学性能,7075铝合金在350℃无润滑条件下进行了5道次的累积叠轧焊实验,通过X射线衍射（XRD）与透射电镜（TEM）分析,研究了7075铝合金在叠轧过程中微观组织的演化规律,利用室温拉伸实验,研究了叠轧道次对7075铝合金力学性能的影响规律,并且采用扫描电镜（SEM）对拉伸断口形貌进行了分析。结果表明：7075铝合金在叠轧过程中材料的组成相η相发生回溶,数量减少;微观组织经历由位错缠结/位错胞状结构向形变亚晶结构转变的过程,5道次后,形成了尺寸小于1μm的亚晶组织;材料的强度随道次的增加而增加,5道次后,其抗拉强度与屈服强度分别达到373.52,315.84 MPa,约为原始合金的1.8倍和3.2倍,同时,延伸率则随着叠轧道次的增加而下降,5道次后,延伸率仅为原始合金的1/3,并且拉伸断裂由韧性断裂转变为脆性断裂。

英文摘要：

In order to improve mechanical properties of 7075 aluminum alloy,7075 aluminum alloy was processed by accumulative roll-bonding（ARB） for 5 cycles without lubrication at 350 ℃.The microstructure evolution was investigated by XRD and TEM,and the effects of cycles on mechanical properties were studied by tensile test at room temperature and the fracture characteristic was analyzed by SEM.The results showed that the η phase of 7075 aluminum alloy redissolved into α phase so that the η phase ratio dropped during the ARB process.The microstructure evolved from dislocation tangle/dislocation cellular to subgrain structure,and subgrain structure formed after 5 cycles,whose grain size was smaller than 1 μm.The strength of the ARB 7075 aluminum increased with cycles,and tensile strength and yield strength reached 373.52 and 315.84 MPa respectively after 5 cycles,which are 1.8 times and 3.2 times of the virgin alloy.Simultaneously,the elongation decreased with cycles,and the elongation was about one third of the virgin alloy after 5 cycles.The tensile failure changed from gliding fracture to brittle fracture with cycles.