微量鋯與安定化處理對5383合金腐蝕與機械性質之影響;Effect of minor Zr and stabilizing treatment on the corrosion and mechanical properties of AA5383 alloys

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Title:	微量鋯與安定化處理對5383合金腐蝕與機械性質之影響;Effect of minor Zr and stabilizing treatment on the corrosion and mechanical properties of AA5383 alloys
Authors:	顏俊宏;Yen, Chun-Hung
Contributors:	機械工程學系
Keywords:	退火;鋁鎂合金;敏化;硝酸重量損失;Al3Mg2;Al3Zr;annealing;Al-Mg alloy;sensitization;NAMLT;Al3Mg2;Al3Zr
Date:	2018-07-24
Issue Date:	2018-08-31 15:01:51 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究藉由微結構觀察、ASTM G67硝酸腐蝕重量損失測試、硬力腐蝕及機械性質測試（硬度、拉伸），探討鋯與安定化處理對AA5383合金機械及腐蝕性質之影響。實驗結果顯示退火溫度是造成鋁鎂合金微結構改變及機械強度變化之主要因素。退火溫度低於250°C為回復結構，退火溫度高於250°C開始轉變為部分再結晶結構。其中，硬度與抗拉強度彼此間呈現正比關係。NAMLT（Nitric Acid Mass Loss Test）及SSRT（ Slow Strain Rate Test）試驗結果顯示，β相腐蝕形態受退火結構影響，其中差排組織及再結晶結構，合金經敏化處理後易使β相沿晶界析出，敏化腐蝕後晶粒呈現剝落腐蝕情形。此外，鋁鎂合金在200~250°C退火，因組成相由α+β轉變成α相，再經敏化後β相析出較為分散且連續性較低，故所產生之晶間腐蝕敏感性及應力腐蝕敏感性均為最低。添加微量鋯之鋁鎂合金因含有Al3Zr顆粒，具有細晶強化及散佈強化效果，使硬度較無添加鋯之合金高，並有效抑制差排滑移及晶粒成長，提升合金再結晶溫度。然而，冷輥及回復階段，因差排組織加速Al3Zr顆粒的粗化成為另一異質成核點，使β相除沿晶界析出外，易於Al3Zr顆粒析出造成材料抗腐蝕性變差。 ;This study explored the effects of zirconium and stabilization on the mechanical and corrosion properties of AA5383 alloys by microstructural observations, ASTM G67 nitric acid corrosion weight loss tests, hard corrosion, and mechanical property tests (hardness, drawing). The results show that the annealing temperature is the main factor to change the microstructure and mechanical strength of Al-Mg alloy. Annealing temperature is lower than 250°c for recovery structure, annealing temperature is higher than 250°c and begins to change into partial recrystallization structure. Among them, the hardness and tensile strength show a direct relationship with each other. The results of NAMLT and SSRT tests show that the β-phase corrosion morphology is affected by the annealing structure. Among them, the poorly-arranged microstructure and recrystallization structure make the β phase precipitate along the grain boundaries after sensitization of the alloy, and the grains exhibit exfoliation corrosion after sensitization and corrosion. In addition, when aluminum-magnesium alloy is annealed at 200-250°C, the composition phase changes from α+β to α-phase, and after sensitization, the β-phase precipitates more dispersed and less continuous, so the intergranular corrosion susceptibility is increased. And stress corrosion sensitivity is the lowest. Aluminum-magnesium alloy containing trace amounts of zirconium contains Al3Zr particles, and has fine-grained strengthening and dispersion strengthening effects, which makes the hardness higher than that of alloys without added zirconium, and effectively inhibits differential row slip and grain growth, and raises the recrystallization temperature of alloys. However, in the chill roll and recovery stage, the coarsening of Al3Zr particles becomes a heterogeneous nucleation site due to the differential structure, so that the β phase is precipitated along the grain boundary, and the Al3Zr particles are easily precipitated and the corrosion resistance of the material deteriorates. After the annealing treatment at a relatively high temperature of 280°C, the aluminum-magnesium alloy containing Zr has the effect of inhibiting recrystallization, and the micro-fibrous structure of the microstructure and the partially recrystallized structure coexist, and the corrosion resistance of the alloy is superior to that of the Zr-free alloy.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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