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Mg-5.5Zn-2Gd-0.6Zr鑄造鎂合金的蠕變機制
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更新時間：2015-10-08
在ZM-1(Mg-5Zn-0.6Zr)合金的基礎(chǔ)上，適量增加Zn的含量并加入重稀土元素Gd，設(shè)計了Mg-5.5Zn-2Gd-0.6Zr實驗合金。采用砂型鑄造工藝制備實驗合金試樣，在不同溫度和應力條件下對該實驗合金和ZM-1合金的蠕變曲線進行了測試。
Mg-5.5Zn-2Gd-0.6Zr鑄造鎂合金的蠕變機制Creep mechanism of Mg-5.5Zn-2Gd-0.6Zr cast alloy
在ZM-1(Mg-5Zn-0.6Zr)合金的基礎(chǔ)上，適量增加Zn的含量并加入重稀土元素Gd，設(shè)計了Mg-5.5Zn-2Gd-0.6Zr實驗合金。采用砂型鑄造工藝制備實驗合金試樣，在不同溫度和應力條件下對該實驗合金和ZM-1合金的蠕變曲線進行了測試。結(jié)果表明：在相同條件下，Mg-5.5Zn-2Gd-0.6Zr實驗合金的穩(wěn)態(tài)蠕變速率較ZM-1合金的降低了一個數(shù)量級；當施加應力為40 MPa時，實驗合金的蠕變激活能Q200?250 ℃=142.0 kJ/mol，接近鎂的自擴散激活能，蠕變受位錯攀移控制，而ZM-1合金在相同應力下蠕變激活能Q200?250 ℃=88.5 kJ/mol，接近鎂的晶界擴散激活能，蠕變受晶界滑移控制。合金在200 ℃條件下的應力指數(shù)n=4.21，而ZM-1合金的應力指數(shù)n=2.21。因此，認為加入重稀土元素Gd后實驗合金的蠕變機制發(fā)生改變，200 ℃時的蠕變機制為位錯攀移機制。
Mg-5.5Zn-2Gd-0.6Zr cast alloy was designed on the base of Mg-5Zn-0.6Zr (ZM-1) alloy by adding Zn and Zr. The experimental alloy samples were prepared by sand casting. The creep curves of the experimental alloy were tested under different temperatures and stresses. The results show that the creep resistance of Mg-5.5Zn-2Gd-0.6Zr alloy is much higher than that of the ZM-1 alloy. The creep activation energy (Q200?250 ℃) of Mg-5.5Zn-2Gd-0.6Zr alloy under the stress of 40 MPa is equal to 142.0 kJ/mol, closing to the self-diffusion activation energy of magnesium, which shows that the dislocation climb plays a dominant role in the creep process of the experimental alloy at stress of 40 MPa. However, the activation energy (Q200?250 ℃) of ZM-1 alloy at stress of 40 MPa is only 88.5 kJ/mol, closing to the grain boundary diffusion activation energy of magnesium, which means that the creep mechanism is grain boundary slip. The stress exponent (n) of experimental alloy at 200 ℃ is equal to 4.21, while the stress exponent of ZM-1 alloy is 2.21. This also indicates that the creep mechanism of Mg-5.5Zn-2Gd-0.6Zr alloy at 200℃ is dislocation climb.
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