Correlation Between Mechanical Properties and Microstructure of Impacted 7075-T6 Aluminium Alloy

7075鋁合金在撞擊下機械性質與顯微結構間之關係

李偉賢(Woei-Shyan Lee) ； 梁寶庭(Pao-Ting Liang)

《中國機械工程學刊》 38卷3期 (2017/06) Pp. 211-219

摘要

7075-T6 aluminium alloy in the longitudinal and transverse directions are impacted at strain rates ranging from 1x10^3s^(-1) to 5x10^3s^(-1) and temperatures of 25°C and 350°C for the longitudinal specimens and 25°C for the transverse specimens. The flow stress increases with increasing strain rate or decreasing temperature. For strain rates higher than 3x10^3 s^(-1), the longitudinal specimens exhibit a greater rate sensitivity than the transverse specimens. The dependence of the flow stress on the strain rate is governed by a power law relation with m=0.187. The stress and temperature dependence of the strain rate is adequately described by the Zener-Hollomon parameter (Z). The higher flow stress is the result of a smaller grain size and a smaller dislocation cell size.

關鍵字

7075-T6 aluminium alloy ； impact ； flow behaviour ； grain ； dislocation

並列摘要

7075 鋁合金具有優異的機械及物理性能性能，已被廣泛應用在交通與航太之結構元件應用。本研究利用哈普金森高速撞擊試驗機，研究不同晶粒方向之7075 鋁合金，在高速撞擊下之動態塑變行為與微觀結構特徵。變形時應變速率控制在1x10^3 ~ 5x10^3s^(-1) 之間，而溫度在縱向晶粒試件分別為25°C 與350°C，另在橫向晶粒試件則為25°C。結果顯示，7075 鋁合金之流變應力、加工硬化率與應變速率敏感性係數隨應變速率的增加而增加，但隨溫度的上升而降低。當應變速率高於3x10^3 時，縱向晶粒試件之應變速率敏感性係數較橫向晶粒試件者為高。而描述流變應力與應變速率關係之m 值為0.187；另流變應力與溫度之關係則可由Zener-Hollomon參數 (Z)來準確的描述。流變阻抗的增加可歸因於較小的晶粒尺寸及差排環尺寸。