均質化處理與Zn/Mg比對Al-Zn-Mg-Cu(AA7095)合金機械性質、應力腐蝕性與淬火敏感性之影響;Effect of Homogenization and Zn/Mg ratio on the mechanical properties, SCC resistance and quench sensitivity of Al-Zn-Mg-Cu (AA7095) alloys

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Title:	均質化處理與Zn/Mg比對Al-Zn-Mg-Cu(AA7095)合金機械性質、應力腐蝕性與淬火敏感性之影響;Effect of Homogenization and Zn/Mg ratio on the mechanical properties, SCC resistance and quench sensitivity of Al-Zn-Mg-Cu (AA7095) alloys
Authors:	李紹晟;Lee, Shao-Cheng
Contributors:	材料科學與工程研究所
Keywords:	Al-Zn-Mg-Cu合金;均質化處理;機械性質;應力腐蝕性;淬火敏感性;Al-Zn-Mg-Cu alloy;homogenization treatment;mechanical properties;stress corrosion resistance;quench sensitivity
Date:	2021-10-26
Issue Date:	2021-12-07 11:59:42 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究藉由微結構觀察、熱分析、機械性質試驗及端面淬火試驗，探討Zn/Mg比(4.6/5.4/6.9)與均質化熱處理對 AA7095(Al-xZn-yMg-2.4Cu (wt%))合金耐腐蝕性、機械性質、淬火敏感性、與熱加工性之影響。結果顯示，含高Mg之低Zn/Mg比合金，經低溫（460°C）均質化處理後，晶界上析出具活性、且低融點之S(Al2CuMg)相，限制了合金熱加工、與固溶溫度，且成為合金破裂之起始點，將導致合金熱加工不易，耐蝕性低、及機械性質（強度與延性）偏低等。而當此高Mg之低Zn/Mg比合金施以兩段均質化(460°C+485°C)後，於低溫均質化所形成的S(Al2CuMg)相，將被充分回溶（dissolved）至鋁基地，消除了S(Al2CuMg)相對合金性質之傷害。含高Mg之中Zn/Mg比合金，也需藉由兩段均質化才得以消除S(Al2CuMg)相，然而，因Zn含量的增加，提升了合金強化相η’(MgZn2)的析出動力、及數量，合金強度也隨之增加。但因非整合強化相的數量高，也導致合金淬火敏感性之提升。而含低Mg之高Zn/Mg比合金，於低溫（460°C）均質化處理後，並無S(Al2CuMg)相之析出，因此可在簡化的均質化程序下，便可獲得良好熱加工，耐蝕性、機械性質（強度與延性）、及低淬火敏感性組合之合金。;In this study, microstructure observation, thermal analysis, mechanical property test and end-quenching test were used to explore the effect of Zn/Mg ratio(4.6/5.4/6.9) and homogenization heat treatment on the mechanical properties, corrosion resistance, quenching sensitivity, and hot workability of AA7095(Al-xZn-yMg-2.4Cu (wt%)) alloys. The results show that the low Zn/Mg ratio alloy with high Mg content, after being homogenized at low temperature (460°C), the active and low melting point S(Al2CuMg) phase precipitates on the grain boundary, which limits the hot working of the alloy. And the solid solution temperature, and become the starting point of alloy fracture, which will result in low hot-workability of the alloy, low corrosion resistance, and low mechanical properties (strength and ductility). When low Zn/Mg ratio alloy with high Mg content is subjected to two stages of homogenization (460°C+485°C), the S (Al2CuMg) phase formed by the low temperature homogenization will be fully dissolved into the aluminum matrix, the damage of S(Al2CuMg) relative to the alloy properties is eliminated. The alloy with high Mg content of medium Zn/Mg ratio, required to execute two-stages homogenization to eliminate the S(Al2CuMg) phase. However, due to the increase in Zn content, the precipitation power of the alloy strengthening phase η′(MgZn2) is increased, therefore the strength of the alloy also increased. However, due to the high number of non-integrated strengthening phases, the quenching sensitivity of the alloy is also increased. For alloys with low Mg content and high Zn/Mg ratio, after homogenization treatment at low temperature (460°C), there is no precipitation of S (Al2CuMg) phase, so good thermal processing can be obtained under simplified homogenization procedures, alloy with combination of corrosion resistance, mechanical properties (strength and ductility), and low quench sensitivity.
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