温度及应力诱发块体非晶合金的结构演化及塑性变形
发布时间：2019-05-19 17:36
【摘要】：块体非晶合金具有高硬度,高强度及高的弹性模量等优异的力学性能,因此是一种应用前景广阔的新型材料。然而,块体非晶合金在室温时没有明显的塑性变形,这制约了非晶合金作为工程结构材料的应用。非晶合金的塑性变形是通过剪切带的方式进行的,因此参与形变的剪切带数量与非晶合金的塑性变形能力密切相关。剪切带数量的提高有赖于形变过程中剪切带的空间增殖,因此本文主要研究温度及应力作用下块体非晶合金的微观结构演化及剪切带空间增殖的关联性,从而进一步来探究温度及应力对其塑性变形的影响。以Zr52.5Cu17.9Ni14.6Al10Ti5(Vit.105)和Mg58Cu30Y10块体非晶合金为研究对象,通过纳米压痕技术,研究了合金在微纳米尺度的室温蠕变行为。结果表明,在微纳米尺度,两种合金的室温蠕变行为均与加载环境有关(如载荷及加载速率),且呈现明显的成分依赖性。如,载荷越大、加载速率越快,蠕变现象越明显,在同等条件下,Mg基非晶合金的蠕变位移比Vit.105合金更大。以Vit.105块体非晶合金为研究对象,研究了温度对非晶合金微观结构演化规律及塑性变形的影响。结果表明,非晶合金应力诱发的结构演化与测试的环境温度密切相关。当试样经40oC预压缩处理时,其自由体积增量最大。较大的自由体积增量为非晶试样形变过程剪切带的空间增殖提供了大量的形核空间,促进了剪切带的增殖,提高了非晶合金的塑性变形能力。当温度继续增加时,自由体积增量减少,剪切带的空间增殖能力减弱,且熔滴及液状脊背的出现使得剪切带在扩展过程中所受阻碍减小,降低了块体非晶合金的塑性变形能力。
[Abstract]:Bulk amorphous alloy has excellent mechanical properties, such as high hardness, high strength and high elastic modulus, so it is a new type of material with broad application prospect. However, there is no obvious plastic deformation of bulk amorphous alloys at room temperature, which restricts the application of amorphous alloys as engineering structural materials. The plastic deformation of amorphous alloys is carried out by shear band, so the number of shear bands involved in deformation is closely related to the plastic deformation ability of amorphous alloys. The increase of the number of shear bands depends on the spatial proliferation of shear bands during deformation. Therefore, this paper mainly studies the relationship between the microstructure evolution of bulk amorphous alloys under the action of temperature and stress and the spatial proliferation of shear bands. In order to further explore the effects of temperature and stress on its plastic deformation. The creep behavior of Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit.105) and Mg58Cu30Y10 bulk amorphous alloys at room temperature was studied by nano-indentation technique. The results show that the creep behavior of the two alloys at room temperature is related to the loading environment (such as loading and loading rate) at micro and nano scale, and shows obvious composition dependence. For example, the higher the load, the faster the loading rate, the more obvious the creep phenomenon. Under the same conditions, the creep displacement of Mg based amorphous alloy is larger than that of Vit.105 alloy. Taking Vit.105 bulk amorphous alloy as the research object, the effect of temperature on the microstructure evolution and plastic deformation of amorphous alloy was studied. The results show that the stress-induced structural evolution of amorphous alloys is closely related to the measured ambient temperature. When the sample is precompressed by 40oC, the free volume increment is the largest. The large free volume increment provides a large amount of nucleation space for the spatial proliferation of shear band during amorphous specimen deformation, promotes the proliferation of shear band and improves the plastic deformation ability of amorphous alloy. When the temperature continues to increase, the free volume increment decreases, the spatial proliferation ability of the shear band weakens, and the appearance of droplets and liquid ridges reduces the hindrance of the shear band in the process of expansion, which reduces the plastic deformation ability of the bulk amorphous alloy.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8
本文编号：2480923
[Abstract]:Bulk amorphous alloy has excellent mechanical properties, such as high hardness, high strength and high elastic modulus, so it is a new type of material with broad application prospect. However, there is no obvious plastic deformation of bulk amorphous alloys at room temperature, which restricts the application of amorphous alloys as engineering structural materials. The plastic deformation of amorphous alloys is carried out by shear band, so the number of shear bands involved in deformation is closely related to the plastic deformation ability of amorphous alloys. The increase of the number of shear bands depends on the spatial proliferation of shear bands during deformation. Therefore, this paper mainly studies the relationship between the microstructure evolution of bulk amorphous alloys under the action of temperature and stress and the spatial proliferation of shear bands. In order to further explore the effects of temperature and stress on its plastic deformation. The creep behavior of Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit.105) and Mg58Cu30Y10 bulk amorphous alloys at room temperature was studied by nano-indentation technique. The results show that the creep behavior of the two alloys at room temperature is related to the loading environment (such as loading and loading rate) at micro and nano scale, and shows obvious composition dependence. For example, the higher the load, the faster the loading rate, the more obvious the creep phenomenon. Under the same conditions, the creep displacement of Mg based amorphous alloy is larger than that of Vit.105 alloy. Taking Vit.105 bulk amorphous alloy as the research object, the effect of temperature on the microstructure evolution and plastic deformation of amorphous alloy was studied. The results show that the stress-induced structural evolution of amorphous alloys is closely related to the measured ambient temperature. When the sample is precompressed by 40oC, the free volume increment is the largest. The large free volume increment provides a large amount of nucleation space for the spatial proliferation of shear band during amorphous specimen deformation, promotes the proliferation of shear band and improves the plastic deformation ability of amorphous alloy. When the temperature continues to increase, the free volume increment decreases, the spatial proliferation ability of the shear band weakens, and the appearance of droplets and liquid ridges reduces the hindrance of the shear band in the process of expansion, which reduces the plastic deformation ability of the bulk amorphous alloy.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8
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，本文编号：2480923
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