| 摘要: | 鋁合金因其重量輕、強度高與耐腐蝕，故廣泛的應用在工業界，材料在經過熱處理與應變成型對於其機械性質影響很大，良好的熱處理與應變成型可以增加其強度，但不良的熱處理也反而會降低材料的機械性質，因此，本研究的目標係建立以非破壞檢測方式評估鋁合金的退火程度(回復、再結晶、晶粒成長)、人工時效析出硬化程度與應變硬化程度。 本實驗使用超音波檢測法(Ultrasonic testing)與渦電流檢測法(Eddy current testing)，以了解鋁合金試片經過不同熱處理與輥壓製程後，其微觀組織與超音波音速、衰減率及渦電流導電特性之關係。實驗材料有純鋁(99.85%)、Al-7005 T6與Al-5052 H32，配合光學顯微鏡（OM）觀察微結構改變，並嘗試以超音波法與渦電流法評估鋁合金的退火程度(回復、再結晶、晶粒成長)、時效硬化程度與應變硬化程度。 實驗結果顯示，退火製程可用音速與導電度變化來評估純鋁、Al-7005 T6/5052 H32試片退火程度(回復、再結晶、晶粒成長)，然而音波衰減率變異過大，故較不適合於檢測材料退火程度。Al-7005人工時效析出製程可用導電度來評估析出硬化程度，而音速與衰減率變異過大，故其較不適合於檢測材料析出硬化程度。Al-5052 H32冷輥壓製程中可以音速，音波衰減率及導電度評估應變硬化程度。 Having the lightweight and higher mechanical strength and corrosion resistance, aluminum alloys have been widely used in industry .The mechanical properties of material were affected by heat treatment and forming process .The fine heat treatment and forming can increase the mechanical strength, but the bad ones will decrease the mechanical strength. The goal of this study is to evaluate the level of annealing treatment(recovery, recrystallization, and grain growth),age precipitation hardening, and strain hardening in Aluminum alloys by NDT(Non-destructive testing) method. This study used Ultrasonic testing and Eddy current testing methods to observe the relations of acoustic velocity, acoustic attenuation, and conductivity to material microstructures through different heat treatments and rolling. These analyses have been performed on three kinds of materials including pure aluminum(99.85 wt.%) , aluminum alloys 7005 T6, and 5052 H32. We used OM to character the variation of microstructures of the annealing treatment (recovery, recrystallization, and grain growth),age hardening, and strain hardening, applying to Ultrasonic testing and Eddy current testing methods to find out their relations simultaneously. The study had three conclusions as follows. First, in pure Al , Al-7005, and Al- 5052 through annealing treatment, there was a good correlation between microstructure and acoustic velocity or conductivity. However, the microstructures did not coincide with the acoustic attenuation which had large variations. Second, we could use conductivity to evaluate the level of age hardening in Al-7005, but acoustic velocity and attenuation did not fit to do it. Finally , in Al- 5052 we could use velocity、attenuation and conductivity to evaluate the level of strain hardening . |
