中文摘要：

为了精确调控Al-Zn-Mg-Cu合金固溶处理过程中第2相的组成和分布,采用配备有Gatan 652加热样品杆的透射电镜原位研究了Al-Zn-Mg-Cu合金中第2相的回溶行为。结果表明：合金在室温下的显微组织由Al基体、MgZn2相、Al2Mg3Zn3相和少量的Al9（Fe,Ni）2相组成。其中,MgZn2相随温度升高的演变过程可以分为3个阶段：第1个阶段,在270℃以下,合金中析出纳米尺度的MgZn2相;第2个阶段,在270-330℃,随着温度的升高,晶内的MgZn2相逐渐回溶,晶界上的MgZn2相开始长大;第3个阶段,在330℃以上,晶界上的MgZn2相逐渐回溶。在实验温度（室温到370℃）内,Al2Mg3Zn3相的尺寸随温度的升高而逐渐增大,Al9（Fe,Ni）2相的尺寸比较稳定,没有明显改变。

英文摘要：

The second phase dissolution in an Al-Mg-Zn-Cu alloy was investigated using in situtransmission electron microscopy（equipped with Gatan 652 double tilt heating holder）.The microstructure of the alloy was found to be composed of the Al matrix,MgZn2,Al2Mg3Zn3 and a spot of Al9（Fe,Ni）2 phase at room temperature.The evolution of the MgZn2 phase consisted of three stages：（i）Below 270 ℃：the precipitation process of the nano-sized MgZn2 phase;（ii）270 ℃ to 310 ℃：the dissolution process of the MgZn2 phase in grain interior into the matrix and coarsening of the MgZn2 phase on grain boundary;（iii）Above330 ℃：the dissolution process of the MgZn2 phase on grain boundary.However,the size of the Al2Mg3Zn3 phase increased with the increase of heating temperature within experimental range（from room temperature to 370 ℃）.The size of the Al9（Fe,Ni）2 phase did not change in this temperature range.