高流变成型法对锆基BMGs的增塑及其伴随作用
发布时间：2019-06-28 19:45
【摘要】：金属玻璃拥有优异的力学与物理性能,但其广泛应用一直受制于其低的室温塑性和差的成型能力。为改变这一现状,本课题组基于Johnson发明的脉冲电流快速热塑性成型法创新并发展出高流变成型方法(HRRF)。前期研究表明,HRRF法可显著强化Zr_(48)Cu_(36)Al_8Ag_8块体金属玻璃(BMG)微观结构不均匀性,大幅提高其压缩塑性。然而,关于该法显著增加Zr基BMGs压缩塑性作用规律的普遍性及其机理仍不清楚,同时,HRRF法对该类金属玻璃的β弛豫、热稳定性、内耗与弛豫行为的作用与规律也缺乏研究。本文以Zr_(48)Cu_(30)Al_8Ag_8Pd_6、Zr45(Cu_5/6Ag_(1/6))48Al7和Zr_(48)Cu_(36)Al_8Ag_8成分BMGs为研究对象,首先通过对金属玻璃HRRF前后样品进行压缩实验,并以SEM观察其表面剪切带和断口形貌,以探索HRRF法对Zr基BMGs增塑作用、规律及其机理。再运用差示扫描量热法(DSC),电阻和内耗技术研究HRRF法对该类金属玻璃β弛豫、热稳定性、内耗与弛豫行为等的作用与规律,以期揭示HRRF方法的增塑作用机理及其相关伴随现象,从而为克服BMGs脆性特征,拓展BMGs工程应用范围提供科学与技术依据。主要成果与结论如下:1.Zr_(48)Cu_(30)Al_8Ag_8Pd_6和Zr45(Cu_5/6Ag_(1/6))48Al7玻璃HRRF前后样品压缩应力-应变曲线表明,HRRF后样品压缩塑性显著提高,且曲线均呈现更明显锯齿波形,反映了HRRF法对Zr基BMGs增塑效果及引起流变行为的改变。压缩样品SEM照片揭示,HRRF后样品表面剪切带数量明显增多,并伴随明显的交割、分叉的特征,同时其断口处剪切脉状花纹致密并出现数量众多的液滴状颗粒,表明了HRRF法对剪切带形成与演化行为及微观结构不均匀性的改变作用。DSC结果显示,HRRF法显著增大样品的放热峰面积,表明该方法增多该类BMGs内部自由体积数量。这些结果从塑性流变行为及微观机制上揭示了该方法增塑的作用本质。2.结合DSC手段,首次以电阻法探索了HRRF法对Zr_(48)Cu_(36)Al_8Ag_8金属玻璃β弛豫及热稳定性作用规律。升温速率10K/min验证表明,电阻法所标定样品的β弛豫开始温度Tβ、一次晶化开始温度T_(x-onset)及其区间等特征参数均与DSC结果相吻合。这证明,电阻法探索β弛豫及热稳定性的有效性。为获得更详细信息,进一步以升温速率1K/min测试了约化电阻率曲线,结果表明,HRRF后样品Tβ大幅提前,且β弛豫所致电阻率变化值Δρrel显著增加,表明该方法显著增强该金属玻璃β弛豫强度。HRRF后T_(x-onset)滞后且晶化温度区间ΔTx变宽,反映该方法提高了该金属玻璃的热稳定性,这一结论得到不同温度淬火样品X衍射结果证实。3.Zr_(48)Cu_(36)Al_8Ag_8金属玻璃HRRF前后样品内耗温度谱揭示,随着温度的升高,HRRF前后样品的内耗均依次表现为线性缓慢增加、较快速非线性增加、急速上升和出现内耗峰的不同变化阶段;内耗频率谱上内耗则依次表现为线性增大、先迅速减小后缓慢增加、先迅速下降后缓慢下降和出现内耗峰。对比HRRF前后样品的温度谱图可发现,HRRF后样品各加载频率下的内耗峰值与内耗峰温均明显高于其相应HRRF前的;对比HRRF前后金属玻璃相同频率谱特征的温度区间范围可知,HRRF后样品β弛豫开始、β弛豫向α弛豫转变均在更低的温度下发生,对应其原子或原子集团运动更加容易;而满足晶化要求的原子结构重排则变得困难,晶化转变的难度加大。
[Abstract]:The metal glass has excellent mechanical and physical properties, but its wide application has been subject to its low room temperature plasticity and poor molding ability. In order to change the present situation, the research group has developed a high-rheological forming method (HRRF) based on the high-speed thermoplastic forming method of the pulse current of Johnson invention. The preliminary study shows that the HRRF method can significantly enhance the microstructure and the compression plasticity of the Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 bulk metallic glass (BMG). However, the general principle and mechanism of the significant increase of the compression plasticity of Zr-based BMGs in this method are still not clear. At the same time, the thermal relaxation, thermal stability, internal friction and relaxation behavior of this kind of metal glass are not studied by the HRRF method. In this paper, the research object of Zr _ (48) Cu _ (30) Al _ 8Ag _ 8Pd _ 6, Zr45 (Cu _ 5/ 6Ag _ (1/6)) 48Al7 and Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 component BMGs is studied, and the surface shear zone and fracture morphology of the metal glass HRRF are studied by means of SEM. By using differential scanning calorimetry (DSC), resistance and internal friction technique, the effects and rules of the HRR method on the relaxation, thermal stability, internal friction and relaxation behavior of this kind of metal glass are studied. And the application scope of the BMGs engineering is expanded to provide scientific and technical basis. The main results and conclusions are as follows: 1.Zr _ (48) Cu _ (30) Al _ 8Ag _ 8Pd _ 6 and Zr45 (Cu _ 5/ 6Ag _ (1/6))48-Al7 glass HRRF sample compression stress-strain curve show that the compression plasticity of the sample after HRRF is obviously improved, and the curve all presents a more obvious sawtooth waveform, which reflects the effect of HRRF on the plasticizing effect of Zr-based BMGs and the change of the rheological behavior. the sem photographs of the compressed samples revealed that the number of shear bands on the surface of the sample after hrf was significantly increased and accompanied by significant delivery, bifurcation characteristics, while the shear pulse pattern at the fracture was dense and a large number of droplet-like particles were present, The effects of HRRF on the formation and evolution of the shear band and the non-uniformity of the microstructure are shown. The DSC results show that the HRRF method significantly increases the heat release peak area of the sample, indicating that the method increases the number of free volumes within this kind of BMGs. These results reveal the effect of this method on the plastic rheological behavior and micro-mechanism. The relaxation and thermal stability of Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 metal glass were investigated by means of resistance method with the means of DSC. The temperature rise rate of 10 K/ min shows that the initial temperature T _ (x-onset) and the interval of the primary crystallization start temperature T _ (x-onset) and its interval are consistent with the DSC results. The results show that the resistance method is effective for exploring the thermal relaxation and thermal stability. In order to obtain more detailed information, the approximate resistivity curve was further tested at a temperature-raising rate of 1 K/ min. The results show that after the HRRF, the temperature of the sample T is significantly advanced, and the value of the resistivity change due to the relaxation is significantly increased, indicating that the method significantly enhances the relaxation strength of the metal glass. The thermal stability of the metal glass is improved by the hysteresis of the T _ (x-onset) and the broadening of the temperature range of the crystallization temperature after the HRRF. The results of the X-ray diffraction of the sample with different temperature quenching show that the temperature profile of the sample in the front and back samples of the HRRF of the Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 metal glass reveals that with the increase of the temperature, The internal friction of the samples before and after the HRRF is shown as a linear slow increase, a faster non-linear increase, a rapid increase and a different phase of the internal friction peak. The internal friction in the internal friction frequency spectrum is shown as a linear increase, and then slowly increases after the rapid decrease, And then the internal friction peak is slowly reduced and the internal friction peak appears after the rapid descent. The temperature profile of the samples before and after the HRRF can be found, and the peak of the internal friction and the temperature of the internal friction peak at each loading frequency of the HRRF sample are obviously higher than that of the corresponding HRRF; and the temperature range of the same frequency spectrum characteristic of the metal glass before and after the HRRF can be seen, and the thermal relaxation of the sample after the HRRF starts, The transition of the initial relaxation and the relaxation is at a lower temperature, and the movement of the atom or the atom group is easier; and the rearrangement of the atomic structure satisfying the crystallization requirement becomes difficult, and the difficulty of the crystallization transition is increased.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8
本文编号：2507564
[Abstract]:The metal glass has excellent mechanical and physical properties, but its wide application has been subject to its low room temperature plasticity and poor molding ability. In order to change the present situation, the research group has developed a high-rheological forming method (HRRF) based on the high-speed thermoplastic forming method of the pulse current of Johnson invention. The preliminary study shows that the HRRF method can significantly enhance the microstructure and the compression plasticity of the Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 bulk metallic glass (BMG). However, the general principle and mechanism of the significant increase of the compression plasticity of Zr-based BMGs in this method are still not clear. At the same time, the thermal relaxation, thermal stability, internal friction and relaxation behavior of this kind of metal glass are not studied by the HRRF method. In this paper, the research object of Zr _ (48) Cu _ (30) Al _ 8Ag _ 8Pd _ 6, Zr45 (Cu _ 5/ 6Ag _ (1/6)) 48Al7 and Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 component BMGs is studied, and the surface shear zone and fracture morphology of the metal glass HRRF are studied by means of SEM. By using differential scanning calorimetry (DSC), resistance and internal friction technique, the effects and rules of the HRR method on the relaxation, thermal stability, internal friction and relaxation behavior of this kind of metal glass are studied. And the application scope of the BMGs engineering is expanded to provide scientific and technical basis. The main results and conclusions are as follows: 1.Zr _ (48) Cu _ (30) Al _ 8Ag _ 8Pd _ 6 and Zr45 (Cu _ 5/ 6Ag _ (1/6))48-Al7 glass HRRF sample compression stress-strain curve show that the compression plasticity of the sample after HRRF is obviously improved, and the curve all presents a more obvious sawtooth waveform, which reflects the effect of HRRF on the plasticizing effect of Zr-based BMGs and the change of the rheological behavior. the sem photographs of the compressed samples revealed that the number of shear bands on the surface of the sample after hrf was significantly increased and accompanied by significant delivery, bifurcation characteristics, while the shear pulse pattern at the fracture was dense and a large number of droplet-like particles were present, The effects of HRRF on the formation and evolution of the shear band and the non-uniformity of the microstructure are shown. The DSC results show that the HRRF method significantly increases the heat release peak area of the sample, indicating that the method increases the number of free volumes within this kind of BMGs. These results reveal the effect of this method on the plastic rheological behavior and micro-mechanism. The relaxation and thermal stability of Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 metal glass were investigated by means of resistance method with the means of DSC. The temperature rise rate of 10 K/ min shows that the initial temperature T _ (x-onset) and the interval of the primary crystallization start temperature T _ (x-onset) and its interval are consistent with the DSC results. The results show that the resistance method is effective for exploring the thermal relaxation and thermal stability. In order to obtain more detailed information, the approximate resistivity curve was further tested at a temperature-raising rate of 1 K/ min. The results show that after the HRRF, the temperature of the sample T is significantly advanced, and the value of the resistivity change due to the relaxation is significantly increased, indicating that the method significantly enhances the relaxation strength of the metal glass. The thermal stability of the metal glass is improved by the hysteresis of the T _ (x-onset) and the broadening of the temperature range of the crystallization temperature after the HRRF. The results of the X-ray diffraction of the sample with different temperature quenching show that the temperature profile of the sample in the front and back samples of the HRRF of the Zr _ (48) Cu _ (36) Al _ 8Ag _ 8 metal glass reveals that with the increase of the temperature, The internal friction of the samples before and after the HRRF is shown as a linear slow increase, a faster non-linear increase, a rapid increase and a different phase of the internal friction peak. The internal friction in the internal friction frequency spectrum is shown as a linear increase, and then slowly increases after the rapid decrease, And then the internal friction peak is slowly reduced and the internal friction peak appears after the rapid descent. The temperature profile of the samples before and after the HRRF can be found, and the peak of the internal friction and the temperature of the internal friction peak at each loading frequency of the HRRF sample are obviously higher than that of the corresponding HRRF; and the temperature range of the same frequency spectrum characteristic of the metal glass before and after the HRRF can be seen, and the thermal relaxation of the sample after the HRRF starts, The transition of the initial relaxation and the relaxation is at a lower temperature, and the movement of the atom or the atom group is easier; and the rearrangement of the atomic structure satisfying the crystallization requirement becomes difficult, and the difficulty of the crystallization transition is increased.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8
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