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Mg-5.5Zn-2Gd-0.6Zr鑄造鎂合金的蠕變機(jī)制
發(fā)布人：上海艾荔艾金屬材料有限公司www.bt990.com.cn
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(shí)驗(yàn)合金。采用砂型鑄造工藝制備實(shí)驗(yàn)合金試樣，在不同溫度和應(yīng)力條件下對該實(shí)驗(yàn)合金和ZM-1合金的蠕變曲線進(jìn)行了測試。
Mg-5.5Zn-2Gd-0.6Zr鑄造鎂合金的蠕變機(jī)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(shí)驗(yàn)合金。采用砂型鑄造工藝制備實(shí)驗(yàn)合金試樣，在不同溫度和應(yīng)力條件下對該實(shí)驗(yàn)合金和ZM-1合金的蠕變曲線進(jìn)行了測試。結(jié)果表明：在相同條件下，Mg-5.5Zn-2Gd-0.6Zr實(shí)驗(yàn)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(dāng)施加應(yīng)力為40 MPa時，實(shí)驗(yàn)合金的蠕變激活能Q200?250 ℃=142.0 kJ/mol，接近鎂的自擴(kuò)散激活能，蠕變受位錯攀移控制，而ZM-1合金在相同應(yīng)力下蠕變激活能Q200?250 ℃=88.5 kJ/mol，接近鎂的晶界擴(kuò)散激活能，蠕變受晶界滑移控制。合金在200 ℃條件下的應(yīng)力指數(shù)n=4.21，而ZM-1合金的應(yīng)力指數(shù)n=2.21。因此，認(rèn)為加入重稀土元素Gd后實(shí)驗(yàn)合金的蠕變機(jī)制發(fā)生改變，200 ℃時的蠕變機(jī)制為位錯攀移機(jī)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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