非等溫時效處理對AA7056合金之機械性質與抗應力腐蝕性質的影響;Effect of non-isothermal aging on the mechanical properties and SCC resistance of AA7056

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题名:	非等溫時效處理對AA7056合金之機械性質與抗應力腐蝕性質的影響;Effect of non-isothermal aging on the mechanical properties and SCC resistance of AA7056
作者:	陳慶;Chen, Ching
贡献者:	材料科學與工程研究所
关键词:	鋁鋅鎂銅合金;非等溫時效處理;回歸再時效處理;腐蝕性
日期:	2022-08-09
上传时间:	2022-10-04 11:13:44 (UTC+8)
出版者:	國立中央大學
摘要:	藉由顯微結構的分析(OM、SEM、TEM、導電度等)，探討連續升溫的非等溫時效(nonisothermal aging，NIA)處理，對Al-9Zn-2.3Mg-1.9Cu (AA7056)鍛造熱處理型合金之機械、耐(剝蝕、應力)腐蝕性質之影響。結果顯示，對於薄試片(2mm)合金，當施以回歸與再時效處理 (retrogression and re-aging, RRA，即T77)後，可獲得不連續的晶界平衡析出η-MgZn2相，及晶粒內細小的析出強化介穩η’-MgZn2相，強度僅略低於頂時效的T6態，但卻提升了合金之抗腐蝕性。但對於厚試片(120mm)時，於所設定之回歸(retrogression)處理時間(30min)，合金並無法達到回歸處理溫度，因而限制了T77對厚試片的應用。相較於T77處理，經非等溫時效(NIA)處理後之AA7056合金，可以在更短處理時間下，使合金晶界產生不連續之平衡η-MgZn2析出相，而晶粒內之介穩η’-MgZn2強化相析出更完全、緻密，不但強度與T77處理相近，且明顯的提升了合金之抗腐蝕性，且 NIA 時效處理較不受合金厚度影響，對於厚材試片在時效過程中，合金內外之實際溫度與所設定之溫度差異極微，因此，NIA 時效處理之 AA7056合金，其時效時間較T77處理短外，且可獲得更佳之強度與抗剝蝕、與抗應力腐蝕性質之組合，更可以克服T77無法處理厚材試片之困擾。 ;Utilizing the microstructure analysis instrument such as OM, SEM, TEM, etc., to explore the Influence of mechanical and (exfoliation, stress) corrosion resistance properties of Al-9Zn-2.3Mg-1.9Cu (AA7056) forged alloys by continuously heated non-isothermal aging. The results show that for the thin materials (2mm), discontinuous grain boundary equilibrium precipitates (η-MgZn2) and the fine grain precipitates (metastable η′-MgZn2) can be obtained through the regression and re-aging treatment (namely T77). The strength is only slightly lower than that of the T6 state, but it improves the corrosion resistance of the alloy. But for the thickt piece (120mm), the alloy could not reach the regression treatment temperature at the set time (30min), thus limiting the application of T77 to the thick alloys. Compared with T77 treatment, non-isothermal aging (NIA) treatment can produce discontinuous equilibrium η-MgZn2 precipitates at the alloy grain boundaries under a shorter time, while the precipitates of the metastable η′-MgZn2 in grains are more finer, not only the strength is similar to that of T77, but also the corrosion resistance of the alloy is significantly improved, and the NIA is less affected by the thickness of the alloy. During the process, the difference between the actual temperature inside and outside the alloy and the set temperature is very small. Therefore, the aging time of AA7056 treated by NIA is shorter than that of T77, and better strength, anti-corrosion, can be obtained. The combination of properties can also overcome that T77 cannot handle thick materials.
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