Zr基块体非晶合金剪切带的自修复及其对合金热学性能的影响
发布时间：2018-09-05 14:41
【摘要】：由于特殊的原子空间排列,非晶合金具有许多优于金属晶体材料的物理、化学性能,使其在体育用品、航空航天、生物应用等很多方面具有极大的应用前景。但是,在室温条件下,非晶合金通过剪切带来获得有限的塑性,这使得其在实际生产应用过程中受到限制。通过非晶合金剪切带的自修复可以延缓剪切带扩展,因此,研究非晶合金剪切带的自修复行为具有重要的理论和实际应用意义。本文以Zr_(65)Cu_(15)Ni_(12.5)Al_(7.5)块体非晶合金作为研究对象,通过在其过冷液相区间进行热处理研究了剪切带的自修复情况;并采用热分析法进一步研究了剪切带自修复对非晶合金热学性能的影响。实验使用的样品为:铸态试样(制备好的试样未做任何处理)、修复前试样(铸态试样产生了2%的压缩塑性变形)、修复试样(对修复前试样进行了自修复)。研究了在不同的热处理条件下试样表面剪切带的自修复情况。结果表明:在633K、643 K和653 K三个不同处理温度下分别修复10 min、20 min和30 min后,试样表面的剪切带都得到了不同程度的修复。在修复温度相同时,随着修复时间的延长,剪切带修复程度越明显;在修复时间相同的情况下,随着修复温度的升高,剪切带修复的程度也越好。XRD测试表明633 K和643 K修复10 min后的试样仍为完全的非晶结构,而其他修复条件下的试样均出现了晶化。采用DSC研究了剪切带修复前后试样热学性能的变化。DSC测试结果表明:在连续升温过程中,650 K下修复10 min后试样的T_g变化不明显,T_x、T_p和ΔT_x明显低于修复前试样的。通过Kissinger方法计算得到的铸态试样、修复前试样和修复试样的玻璃转变激活能分别为252 kJ/mol、263 kJ/mol和270 kJ/mol,晶化激活能分别为238 kJ/mol、255 kJ/mol和296 kJ/mol。在等温晶化过程中,修复后试样的孕育时间明显缩短。通过Johnson-Mehl-Avrami(JMA)方法计算得到的铸态试样、修复前试样和修复试样的Avrami指数n值的范围分别是1.698~1.991、2.273~2.446和2.15~2.30,表明其等温晶化方式都是晶核生长受扩散控制的初晶型或共晶型晶化,并且形核和长大速率随时间减小;三种试样的有效晶化激活能分别为448 kJ/mol、457 kJ/mol和333 kJ/mol。
[Abstract]:Because of the special atomic space arrangement, amorphous alloys have many better physical and chemical properties than metallic crystal materials, which make them have great application prospects in many fields such as sports products, aerospace, biological applications and so on. However, at room temperature, the amorphous alloy can obtain limited plasticity by shear, which makes it limited in practical application. The self-repair of the shear band of amorphous alloy can delay the expansion of the shear band. Therefore, it is of great theoretical and practical significance to study the self-repair behavior of the shear band of amorphous alloy. In this paper, Zr_ (65) Cu_ (15) Ni_ (12. 5) Al_ (7. 5) bulk amorphous alloys were used to study the self repair of shear bands by heat treatment in its subcooled liquid phase, and the effect of self repair of shear bands on the thermal properties of amorphous alloys was further studied by thermal analysis. The samples used in the experiment are as follows: as-cast samples (without any treatment of the prepared samples), pre-repair samples (the as-cast samples produced 2% compressive plastic deformation), and the repaired samples (self-repair of the pre-repair specimens). The self-repairing of shear bands on the surface of specimens under different heat treatment conditions was studied. The results showed that the shear bands of the samples were repaired at different temperatures of 633K 643K and 653K for 10 min,20 min and 30 min, respectively. When the repair temperature is the same, the extent of shear band repair becomes more obvious with the prolongation of repair time, and when the repair time is the same, with the increase of repair temperature, The results show that the samples repaired at 633K and 643K for 10 min are still amorphous, while the samples under other repair conditions are crystallized. The changes of thermal properties of the specimens before and after the shear band repair were studied by DSC. The results of DSC test showed that the changes of T _ (T _ g) of the samples repaired for 10 min at 650K during the continuous heating process were not obvious, and the changes of T _ (T) _ p and 螖 T _ Stax were obviously lower than those of the samples before and after the repair. The activation energies of glass transition of as-cast samples calculated by Kissinger method were 252 kJ/mol,263 kJ/mol and 270 kJ/mol, crystallization activation energies of 238 kJ/mol,255 kJ/mol and 296 kJ/mol., respectively. During isothermal crystallization, the inoculation time was shortened obviously. The range of Avrami exponent n of as-cast samples calculated by Johnson-Mehl-Avrami (JMA) method is 1.6981.991U 2.273N 2.446 and 2.152.30 respectively, which indicates that the isothermal crystallization mode is either primary or eutectic type controlled by diffusion of nucleation. And the nucleation and growth rates decreased with time, and the effective crystallization activation energies of the three samples were 448 kJ/mol,457 kJ/mol and 333 kJ/mol., respectively.
【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8
[Abstract]:Because of the special atomic space arrangement, amorphous alloys have many better physical and chemical properties than metallic crystal materials, which make them have great application prospects in many fields such as sports products, aerospace, biological applications and so on. However, at room temperature, the amorphous alloy can obtain limited plasticity by shear, which makes it limited in practical application. The self-repair of the shear band of amorphous alloy can delay the expansion of the shear band. Therefore, it is of great theoretical and practical significance to study the self-repair behavior of the shear band of amorphous alloy. In this paper, Zr_ (65) Cu_ (15) Ni_ (12. 5) Al_ (7. 5) bulk amorphous alloys were used to study the self repair of shear bands by heat treatment in its subcooled liquid phase, and the effect of self repair of shear bands on the thermal properties of amorphous alloys was further studied by thermal analysis. The samples used in the experiment are as follows: as-cast samples (without any treatment of the prepared samples), pre-repair samples (the as-cast samples produced 2% compressive plastic deformation), and the repaired samples (self-repair of the pre-repair specimens). The self-repairing of shear bands on the surface of specimens under different heat treatment conditions was studied. The results showed that the shear bands of the samples were repaired at different temperatures of 633K 643K and 653K for 10 min,20 min and 30 min, respectively. When the repair temperature is the same, the extent of shear band repair becomes more obvious with the prolongation of repair time, and when the repair time is the same, with the increase of repair temperature, The results show that the samples repaired at 633K and 643K for 10 min are still amorphous, while the samples under other repair conditions are crystallized. The changes of thermal properties of the specimens before and after the shear band repair were studied by DSC. The results of DSC test showed that the changes of T _ (T _ g) of the samples repaired for 10 min at 650K during the continuous heating process were not obvious, and the changes of T _ (T) _ p and 螖 T _ Stax were obviously lower than those of the samples before and after the repair. The activation energies of glass transition of as-cast samples calculated by Kissinger method were 252 kJ/mol,263 kJ/mol and 270 kJ/mol, crystallization activation energies of 238 kJ/mol,255 kJ/mol and 296 kJ/mol., respectively. During isothermal crystallization, the inoculation time was shortened obviously. The range of Avrami exponent n of as-cast samples calculated by Johnson-Mehl-Avrami (JMA) method is 1.6981.991U 2.273N 2.446 and 2.152.30 respectively, which indicates that the isothermal crystallization mode is either primary or eutectic type controlled by diffusion of nucleation. And the nucleation and growth rates decreased with time, and the effective crystallization activation energies of the three samples were 448 kJ/mol,457 kJ/mol and 333 kJ/mol., respectively.
【学位授予单位】：烟台大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8
【参考文献】
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