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7A52鋁合金中第二相分析及微區(qū)電位測試
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更新時間：2015-11-27
采用金相顯微鏡、掃描電鏡及能譜、透射電鏡、掃描開爾文探針力顯微鏡對7A52鋁合金的第二相進(jìn)行觀察及表征，并對微米量級的第二相進(jìn)行電位測試。
7A52鋁合金中第二相分析及微區(qū)電位測試Analysis of secondary phases and measurement of?volta potential of 7A52 aluminum alloy
采用金相顯微鏡、掃描電鏡及能譜、透射電鏡、掃描開爾文探針力顯微鏡對7A52鋁合金的第二相進(jìn)行觀察及表征，并對微米量級的第二相進(jìn)行電位測試。結(jié)果表明：長條狀的η相與基體非共格，其強(qiáng)化效果較弱；圓片狀的η' 相與基體半共格，是最主要的時效強(qiáng)化相；近似方塊狀的Al6Mn分布在晶界和晶內(nèi)；近似于球形的Al3Zr粒子尺寸小、密度大，能夠強(qiáng)烈地釘扎位錯；形狀不規(guī)則的AlMnFe和Mg2Si沿軋制方向彌散分布在基體上，其伏打電位均低于基體的電位，在腐蝕環(huán)境中容易被溶解而腐蝕，成為應(yīng)力腐蝕裂紋源；而且同類相的尺寸不同，AlMnFe相對基體的伏打電位值也不同；Al6(Mn,Fe)相對基體的伏打電位值要比Mg2Si的更低，說明在腐蝕環(huán)境中，Al6(Mn,Fe)更容易被腐蝕。本試驗有助于分析應(yīng)力腐蝕斷裂中裂紋的起始點(diǎn)。
The metallographic microscope, scanning electron microscope, energy dispersive spectrometer, scanning Kelvin probe force microscope were used to observe and characterize the secondary phases of 7A52 aluminum alloy, and the volta potential of micron dimension secondary phases was tested. The results indicate that the h phase in long strip shape is incoherent with the matrix, whose strengthening effect is relatively weak. The η' phase in disk shape semi coherent with the matrix is the most important ageing strengthening phase. The Al6Mn precipitates in approximate square block shape distribute in the grains and grain boundaries. The Al3Zr precipitates in ball shape are very small and their density is very high, forming a strong pinning effect on the dislocations. The irregularly shaped intermetallics AlMnFe and Mg2Si disperse along the rolling direction in the matrix, and their volta potentials are lower than those of the matrix. Hereby, they are easy to be dissolved and corroded in erosive environments, thus becoming the stress corrosion cracking initiation sites. The same second phase with different sizes show different relative volta potentials to the matrix. The volta potential of AlMnFe is lower than that of Mg2Si intermetallics, which means that AlMnFe intermetallics are easier to be corroded in erosive environments. These measurement results will help in the crack initiation analysis in stress corrosion cracking.
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