純鋁與鋁鎂矽合金微結構對超音波衰減率的影響

The ultrasonic attenuation study for dislocation, grainboundary and precipitates morphologies of pure aluminum and Al-Mg-Si alloy.

魏兆廷(Chao-ting Wei)

指導教授 ： 施登士

國立中央大學/工學院/機械工程學系/碩士(2011年)

摘要

本實驗使用超音波檢測法量測5N純鋁與Al6063鋁合金材料的超音波衰減率。討論基地中晶界與晶界內基地對音波衰減率的影響（ 值與B值）。藉由背向散射電子繞射分析（Electron Back-Scatter Diffraction，EBSD）量測不同角度晶界，將晶界對衰減率的影響區分為低角度（0 o ~ 5o）、中角度（5 o ~ 15o）、高角度（15 o ~ 65o）晶界長度比例參數對衰減率的影響。晶界對衰減率的影響為（ 值），B值為基地對衰減率的影響。經計算超音波訊號與純鋁內部差排的關係後，音波衰減率對差排密度的影響較靈敏，但差排密度與差排環的長度及密度不易精確計算，因此容易在計算上發生誤差。
　　超音波衰減率的 dB（將20MHz超音波衰減率和5MHz超音波衰減率相減）可以增加衰減率變化的敏感度。觀察Al6063經不同降溫速率的退火後晶粒尺寸的變化與 dB成正比。 dB與Al6063自然時效的微硬度變化可看出兩個階段：第一階段為團聚物（Mg-cluster、Si-cluster、co-cluster）的成核及生長，衰減率差值隨著時效時間增加（微硬度增加）而遞減；第二階段為團聚物的穩定成長或整合，此階段微硬度及衰減率差值變化不明顯。

關鍵字

自然時效 ； 晶界 ； 超音波衰減率 ； 晶粒尺寸

並列摘要

The study used ultrasonic testing to obtain the attenuation of 99.999% pure aluminum and 6063 aluminum alloy. As the result, the measured attenuation is sensitively in varied dislocation density or dislocation loop, so that would increase the calculation errors. Furthermore, we measure attenuation and separate into two parts for discuss: i) grain boundaries set as ; The grain boundary on attenuation were divided to varied angle boundaries (low angle: 0 o ~ 5o, middle angle: 5 o ~ 15o, high angle: 15 o ~ 65o). The angle of grain boundaries of 5N pure Al was observed by using electron back scatter diffraction (EBSD), and estimated the relation between the grain boundary fractions and attenuation. And ii) matrix set as B value.
　　The subtraction of the ultrasonic attenuation of high frequency and low frequency would increase the sensitivity of the difference of the attenuation. The change of grain size of annealed Al6063 by different cooling rate can observed from the subtraction of the ultrasonic attenuation. There are two stages were observed from the subtraction of the ultrasonic attenuation varying micro-hardness of Al6063 during T4 process (nature aging). One is the nucleation and growth of solute atoms (Mg-cluster、Si-cluster). The subtraction decreases with the increasing of the aging time. The other stage is the steady growth or coalescence of clusters. The changes of the subtraction and micro-hardness are unapparent.

並列關鍵字

ultrasonic attenuation ； nature aging ； grain boundary ； grain size

參考文獻

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