自然時(shí)效對Al-Zn-Mg合金型材抗應(yīng)力腐蝕性能的影響

自然時(shí)效對Al-Zn-Mg合金型材抗應(yīng)力腐蝕性能的影響Effect of natural aging time on stress corrosion cracking of aluminum alloy

采用電導(dǎo)率實(shí)驗(yàn)與慢應(yīng)變速率拉伸實(shí)驗(yàn)研究自然時(shí)效對Al-Zn-Mg合金型材應(yīng)力腐蝕斷裂的影響，通過掃描電鏡、透射電鏡等顯微組織分析揭示其性能變化的機(jī)理。結(jié)果表明：Al-Zn-Mg合金型材的電導(dǎo)率隨著自然時(shí)效時(shí)間的延長呈下降趨勢，停放至28 d左右基本達(dá)到穩(wěn)定狀態(tài)，穩(wěn)定后合金的內(nèi)、外表層電導(dǎo)率分別為32.20(IACS)%與31.50(IACS)%。自然時(shí)效后再進(jìn)行人工時(shí)效((90 ℃, 12 h)+(169 ℃, 11 h))，Al-Zn-Mg合金型材的抗拉強(qiáng)度(Rm)隨自然時(shí)效時(shí)間的延長而顯著降低，但合金的抗應(yīng)力腐蝕性能明顯提高；自然時(shí)效后，合金內(nèi)晶界無沉淀析出帶變寬(PFZ)，晶界析出相尺寸與間距變大。

The effect of natural aging time on stress corrosion cracking of aluminum alloy was investigated by means of electrical conductivity and slow rate tension testing (SSRT). The changing mechanism was analyzed by scanning electron microcopy (SEM) and transmission electron microcopy (TEM). The results show that the electrical conductivity of alloy decreases during natural aging time at room temperature and reaches a stable value after natural aging about 28 d. The electrical conductivities of different surfaces of alloy are 32.2(IACS)% and 31.5(IACS)%, respectively. The stress corrosion cracking resistance can be improved after natural aging time at room temperature. The strength decreases sharply. The grain boundary precipitates distribute coarsely and sparsely after natural aging time about 28 d. The precipitate free zone (PFZ) width becomes broaden, and the alloy possesses the best resistance to SCC.

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