摘要
The quenching sensitivity of AA7136 alloy was investigated by time−temperature−property(TTP)diagrams,and the heterogeneous precipitation behavior during isothermal holding was investigated using scanning electron microscopy,scanning transmission electron microscopy and high resolution transmission electron microscopy.Based on 99.5%TTP diagram,the nose temperature is determined to be about 346℃ with the transformation time of about 0.245 s.The precipitation ofη(MgZn_(2)),T(Al_(2)Zn_(3)Mg_(3)),S(Al_(2)CuMg)or Cu−Zn-rich Y phases can be found depending on isothermal holding temperature and time,and it is described in a time−temperature−precipitation diagram.The size and area fraction of isothermal holding induced phase particles increase,which results in the decrease of hardness of samples after aging.The quantitative contribution to loss of hardness by grain boundaries/subgrain boundaries and dispersoids in the matrix is discussed based on the amount of heterogeneous precipitation related to them.
通过时间-温度-性能(TTP)曲线研究AA7136合金的淬火敏感性,使用扫描电镜、扫描透射电镜和高分辨电镜研究等温保温过程中的非均匀析出行为。结果显示,99.5%TTP曲线的鼻尖温度约为346℃,鼻尖处的转变时间约为0.245 s。在不同等温保温样品中观察到η(MgZn_(2))相、T(Al_(2)Zn_(3)Mg_(3))相、S(Al_(2)CuMg)相或富Cu-Zn的Y相,并将这些相的析出行为描述在TTP曲线中。随着保温时间的延长,这些平衡相的尺寸和面积分数增大,导致样品时效后的硬度降低。根据晶界/亚晶界和晶内弥散粒子上非均匀析出第二相的数量分析它们对硬度下降的定量贡献。
基金
financial supports from the National Key Research and Development Program of China (No. 2016YFB0300901)
the Scientific Research Project of Inner Mongolia Colleges and Universities, China (No. NJZY21092)。
