Abstract
The precipitation behavior of a 7075 Al alloy during isochronal heat treatments at three different heating rates has been studied using differential scanning calorimetry,high-angle-annular-dark-field scanning-transmission-electron microscope and density functional theory calculation.In the early stage of aging,GPⅠ and GPⅡ zones form sequentially and cause two characteristic DSC peaks.Subsequently,the formation of η1 precipitates takes place concurrently with η'.A novel type of metastable phase ηi'is identified as the precursor of η1,which can lower the lattice misfit between η1 and Al matrix along the direction of[10(1)0]η1//[001]Al.Accordingly,a pathway for the formation of η1 via η1'is demonstrated.Precipitates η'together with η1 and η1'contribute to the third DSC peak.With the further increase of temperature,ηprecipitates become prevailing.Based on the quantitative analyses,the influence of the heating rate and ending temperature on the cross section and number density of phases formed is discussed.
基金项目
This work was financially supported by the National Natural Science Foundation of China(52071284)
This work was financially supported by the National Natural Science Foundation of China(51771172)
NETL
NSTL
维普
万方数据