陈鼎,张艳斌,王维.Y对高锌镁合金的拉伸蠕变行为的影响[J].湖南大学学报:自然科学版,2015,42(6):53~59
Y对高锌镁合金的拉伸蠕变行为的影响
Tensile Creep Behavior of Y Addition in High Zinc Magnesium Alloy
  
DOI:
中文关键词:  蠕变抗力  Mg-Zn-Y;第二相;稀土Y  蠕变机制
英文关键词:creep resistance  Mg-Zn-Y  second phase  ytterbium  creep mechanism
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作者单位
陈鼎,张艳斌,王维 (湖南大学 材料科学与工程学院湖南 长沙410082) 
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中文摘要:
      采用扫描电镜,X射线衍射仪以及高温蠕变试验机等试验手段研究了Y含量对Mg-5.5Zn重力铸造镁合金抗蠕变性能和应力指数的影响.结果表明:随着Y含量的增加,Mg-5.5Zn合金中依次出现了Mg7Zn3,Mg3Zn6Y(I-相)和Mg3Zn3Y2(W-相)3种不同类型的强化相,而合金中第二相种类、体积分数发生变化,导致抗蠕变性不断提高.在同样的蠕变条件下,高熔点稀土相比低熔点Mg7Zn3相更能降低合金的稳态蠕变速率.Mg-5.5Zn-(0.7,1.5,3.5)Y(wt%)3种合金在175 ℃/50~60 MPa下的应力指数n分别为5.2,3.2和2.2,在200 ℃/50~60 MPa下应力指数n分别为11.0,3.8和2.9.Mg-5.5Zn-0.7Y合金在175 ℃/55 MPa和200 ℃/55 MPa条件下的蠕变机制分别为位错攀移和Power-Law方程失效.Mg-5.5Zn-(1.5,3.5)Y两种合金在175~200 ℃/50~60 MPa范围下的蠕变机制是位错粘滞运动.
英文摘要:
      The effect of earth element Y addition on the creep properties and creep stress exponent of Mg-5.5Zn gravity cast magnesium alloy was investigated by using scanning electron microscopy(SEM),X-ray diffraction(XRD) and creep property testing at elevated temperature. The results show that, with the increase of yttrium content in Mg-5.5Zn (wt%)alloy ,three second phases,Mg7Zn3,Mg3Zn6Y(I-phase)and Mg3Zn3Y2(W-phase), are found. The variety categories and the increasing volume fraction of the second phase cause the increase of the creep resistance obviously. Compared with Mg7Zn3 phase, rare earth phases have a high melting point and it have a stronger effect for reducing the creep rate of alloy in the same given creep conditions. When the applied stresses are 50~60 MPa at the temperature 448 K, the calculated stress exponent n is 5.2, 3.2, and 2.2, respectively for the as-cast Mg-5.5Zn-Χ%Y(Χ=0.7,1.5,3.5)alloys. The results indicate that the rate controlling mechanism of Mg-5.5Zn-0.7Y alloy at 175 ℃/55 MPa and 200 ℃/55 MPa is respectively the dislocation creep and power law breakdown,and the creep mechanism of Mg-5.5Zn-(1.5,3.5)Y two alloys is dislocation viscous motion at the applied stresses of 50~60 MPa and the temperature of 448~473 K.
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