本研究藉由微結構觀察、導電度(%IACS)、熱差分析(DSC)與機械性質等的量測分析，來探討A201(Al-Cu-Mg-Ag)可熱處理型高強度鑄造鋁合金固溶淬火處理後，經不同時間 (未實施、1天、4天) 的自然時效，對後續過時效熱處理(T7:190℃*5hrs)合金的之抗應力腐蝕性(SCC)的影響。 結果顯示，當自然時效時間由1天增加至4天時，析出強化原子在鋁合金基地中的聚集(clustering)將增強，此時，合金之導電度較固溶態合金分別下降了約5.5%與6.2%，DSC分別增加了約36%與37%，而硬度則分別上升了40%與54%；當合金未進行、與進行1天與4天之自然時效後，施以過時效熱處理(T7)時，此時合金之導電度將較其自然時效態(未實施、1天、4天)分別提升了6.5%，12.7%與13.4%；而硬度則分別提升了112%，53%與30%。 且藉由慢應變速率拉伸試驗，來測試合金於海水中的抗應力腐蝕性(SCC)特性，顯現自然時效有明顯提升抗SCC效果，結果顯示A201-T7態合金延性損失率由未實施自然時效的28%，降至實施自然時效(1天與4天)的~5%，拉伸強度損失率則由未實施自然時效的15%，降至實施自然時效的~3%；這些都充分顯現固溶淬火後的自然時效，對於提升A201-T7態合金之抗應力腐蝕性(SCC)是必須的；以上的結果也顯示1天與4天之自然時效，不僅對提升T7態A201合金之抗應力腐蝕性(SCC)的效果相近，且對於微結構(導電度、DSC之分析)與機械性質之影響效果也是差異並不大。 ;This research presents the effect of different nature aging time (without aging, 1day, 4day) ,which the process is between solution treatment and T7 artificial aging ,on the resistance of stress corrosion cracking of high strength A201(Al-Cu-Ag-Mg) aluminum alloys , the analyzed methods including optical microscope (OM), electrical conductivity meter (% IACS), tensile test...ellipses.
It shows that the clustering of precipitation atoms in the aluminum alloy base will be enhanced when the natural aging time is increased from 1 day to 4 days. Compared to quenched-state alloys, the conductivity of alloys decreased about 5.5% and 6.2% respectively after 1day and 4days natural aging while the peak area of DSC increased about 36% and 37% and the hardness increased 40% and 54%. Compared to nature aging state(without aging, 1day, 4days), the conductivity of the alloy increased by 6.5%, 12.7% and 13.4% after T7 artificial aging while the hardness increased by 112%, 53% and 30% respectively. The resistance of the stress corrosion cracking (SCC) of the alloy were analyzes by slow strain rate tensile test in seawater. The results showed the resistance of SCC were improved significantly with the increasing time of nature aging.The ductility loss rate was 28% of the alloy without natural aging and the rate of natural aging alloys(1 day and 4 days) were both 5%. The tensile strength loss rate was 15% of the alloy without natural aging and the rate of natural aging alloys(1 day and 4 days) were both 3%.
The results showed natural aging is important to improve the resistance of SCC for the A201-T7. Microstructure (electrical conductivity meter, DSC), mechanical properties and the resistance of SCC ability shows no different with the natural aging 1 day and 4 days for the A201-T7.
