預時效及預變形處理對高強度Al—Mg—Si—Cu合金顯微組織及機械性質之影響

The Effect of Preaging and Predeformation Treatment on The Microstructure and Mechanical Properties of High Strength Al—Mg—Si—Cu Alloys

許家誠(Chia-Cheng Hsu)

指導教授 ： 邱傳聖 ； 洪衛朋

元智大學/工程學院/機械工程學系/碩士(2004年)

摘要

本研究旨在探討預時效處理及預變形處理對於高強度Al—Mg—Si—Cu合金的影響。較高含Cu量的6013B鋁合金在T6處理期間發生晶粒過度粗化之現象因而強度受到明顯的弱化，但是在硬度方面卻與6013A鋁合金相似。然而6013B鋁合金之強度弱化現象藉由T8處理可獲得有效的改善，經由顯微結構觀察發現此乃變形帶及次晶粒的產生所形成，其最大強度可達到455MPa。而在6013A鋁合金方面，其T8處理之強度與T6處理相似，此乃由於其變形擠壓比的不足導致變形帶及次晶粒無法有效地產生。經由T8P1製程此研究有效地開發出抗拉強度高達499MPa之高強度6013B鋁合金，然而6013A鋁合金也能因T8P1製程有效的將合金強度提升至478MPa的高強度。
藉由低溫晶粒細化之R14T6熱處理可有效改善6013B鋁合金之晶粒粗大及強度弱化現象，進而得到一晶粒大小約為25μm之微細等軸晶晶粒，其拉伸強度也可提升至435MPa之高強度。而在6013A鋁合金方面，雖然經R14T6熱處理可使其晶粒大小細化至27μm之微細等軸晶晶粒，但由於其晶粒細化幅度不大，因此在其機械性質上與傳統T6熱處理相較之下並無顯著的提升現象。然而依據晶粒細化原理，此研究於R16T6及R18T6兩試驗中更進一步獲得更為微細之等軸晶晶粒。
6013A鋁合金之F材經魚麟式縱向及橫向焊接後於其顯微結構組織可觀察到巨大裂縫及沿晶裂紋，經由檢測發現此液化裂縫型態乃是屬於過量Si原子的低熔點Mg2Si之共晶熔融相，然而經由晶粒細化製程後之R14T6細晶材也無法有效抑制液化裂縫的發生，只能抑制其裂縫發生的數量及長度。

關鍵字

Al—Mg—Si—Cu合金 ； 6013鋁合金 ； 預時效處理 ； 預變處理形 ； 晶粒細化 ； 液化裂縫

並列摘要

The purpose of this study was to determine the effect of the preaging treatment and predeformation treatment on the strength of Al—Mg—Si—Cu alloy. The 6013B alloy of higher Cu content occurred that the phenomenon of the grains over-grown in the conventional T6 heat treatment, and therefore the strength of the 6013B alloy was subjected to decrease, but both alloys similar hardness properties. Nevertheless, the phenomenon of feeble strength has been improved effectively by way of T8 treatment due to the deformation bends and subgrains were resulted from the 6013B alloy, the tensile strength can be achieved to 455MPa. The strength of the 6013A alloy is similar with the T6 treatment due to its deformed reduction insufficient lend to unable to produce the deformation bends and subgrains in T8 treatment. The high-strength 6013B alloy has been developed by way of T8P1 process, the tensile strength can achieve 499MPa, and than the tensile strength of the 6013A alloy can also be achieved to 478MPa.
The R14T6 treatment of lower temperature grain refinement has been effectively improved the phenomenon of over-big grain and feeble strength in the 6013B alloy, and obtained a refined equiaxed grain that the grain size about 25μm, and than its tensile strength can also be achieved to 435MPa. Although the 6013A alloy can be refined the grain up to 27μm, but its mechanical properties has been not outstandingly increased than the conventional T6 treatment due to its grain refinement range isn’t large. In accordance with the principle of grain refinement, the both alloys have been obtained even more refined equiaxed grain by way of the R16T6 and R18T6 research.
The microstructure was observed the phenomenon of immense crack and intercrystalline crack for as extrusion of the 6013A alloy after the transverse and longitudinal fishskin mode welding, and the liquation cracks were discovered that it is existed the low fusion point eutectic phase of Mg2Si with excess Si by way of high power optical microscope and scanning electron microscope and energy dispersion X-ray analysis. The R14T6 materials of the refined grain were also restrained that the liquation cracks were resulted after the grain refinement, the creases are merely decreased that the amount and length of the liquation cracks were arose.

並列關鍵字

Al—Mg—Si—Cu alloys ； 6013 alloys ； preaging treatment ； predeformation treatment ； grain refinement ； liquation cracking

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