【作者】 周建坤；

【导师】 边秀房；

【作者基本信息】 山东大学 ， 材料加工工程， 2005， 硕士

【摘要】 本文以铝基非晶为研究对象,通过X射线衍射（XRD）和结构分析软件等主要手段,系统的研究了Al-Ni-Pr非晶合金的中程有序结构。实验结果表明,Al_100-xNi₁₀Pr_x（x=3,5,7,9）四种非晶合金中都存在中程有序结构,其结构因子的预峰峰位随稀土元素Pr含量的增加而向小角度（小Q处）偏移,中程有序结构的结构单元尺寸R随稀土元素Pr含量增加而变大。同时通过差示扫描量热计（DSC）对Al-Ni-Pr非晶合金的非晶形成能力进行了计算,计算结果表明,随稀土元素Pr含量的增加,其约化玻璃转化温度升高,非晶形成能力提高。这与中程有序结构的变化趋势相同。由此可见,铝基非晶合金的中程有序结构与其非晶形成能力存在密切关系。 通过X射线衍射（XRD）、差示扫描量热计（DSC）、透射电子显微镜（TEM）、高分辨电镜（HRTEM）等主要手段对Al-Ni-Pr非晶合金的晶化过程的研究发现,Al₈₇Ni₁₀Pr₃非晶合金的晶化过程归纳如下:非晶基体→非晶+fcc-Al→fcc-Al+Al₃Ni+AlPr;而Al₈₅Ni₁₀Pr₅非晶的晶化过程为:非晶基体→非晶+fcc-Al+Al₃Ni+AlPr→fcc-Al+Al₃Ni+AlPr。等温DSC实验结果表明,Al₈₇Ni₁₀Pr₃非晶合金为初晶型晶化,而且其初晶相晶化为长大机制控制。 以铝镍基非晶形成熔体为研究对象,通过高温熔体粘度仪测量了铝镍基非晶形成熔体的粘度;利用熔甩法制备了铝镍基非晶薄带,并通过DSC对非晶薄带进行晶化,从而得到其玻璃转变的各种物理参数:使用了一个新参数——过热熔体脆性M来表征合金熔体的粘度在液相线温度处的相对变化率大小,进一步结合铝镍基非晶形成熔体的粘度结果及其非晶晶化的参数,通过计算结果发现,在铝镍基非晶合金中,过热熔体脆性M值越大,其非晶形成能力越小,因此我们可以将M看作一个衡量铝基非晶形成能力大小的新参数。更多还原

【Abstract】 In this paper, the amorphous structures of Al-Ni-Pr alloys with different compositions have been systematically studied by X-ray diffraction (XRD). The results of our experiments show that a distinct prepeak which characterizes medium-range order (MRO) occurs in the structure factors of each amorphous alloy. The position of the prepeak shifts to smaller Q values as the concentration of Pr increases. The structure unit size increases with increasing Pr concentration. The glass forming ability (GFA) of Al-Ni-Pr alloys has been calculated by differential scanning calorimetry (DSC). The results show that the addition of Pr elevates the reduced glass transition temperature, and increases the GFA of amorphous Al-Ni-Pr alloys which is in agreement with the medium-range order. Therefore, the medium-range order is closely related to the glass forming ability in amorphous Al-Ni-Pr alloys.The crystallization behaviour of amorphous Al-Ni-Pr alloys has been investigated by XRD, DSC, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) techniques. It has found that the crystallization behaviour of Al87Ni10Pr3 can be expressed as follows: Fully amorphous→amorphous + fcc-Al→fcc-Al + Al3Ni + AlPr; and Al85Ni10Pr5 has a different process which can be expressed as: Fully amorphous→amorphous + fcc-Al+ Al3Ni + AlPr→fcc-Al + Al3Ni + AlPr. Crystallization processe of Al87Ni10Pr3 amorphous alloy has the typical features of primary crystallization. And the monotonously decreasing isothermal calorimetric signal, characteristic of a grain growth process has been observed in the course of precipitation of fcc-Al inAl87Ni10Pr3.This paper presents the viscosity behaviour of Al-Ni-based glass forming melts.Viscosity measurements on molten alloys were made using an oscillating viscometer. The amorphous Al-Ni-based ribbons were produced by the single roller melt-spinning technique under an argon atmosphere. The parameters of the crystallization in amorphous Al-Ni-based ribbons have been identified by using DSC analysis. Then, from the value of its viscosity and the parameters of its crystallization, a new concept, the fragility of superheated melt M has been calculated. It has been found that this kind of fragility value of liquid above liquidus temperature is closely related to the glass forming ability in Al-Ni-based amorphous alloys. The less the value of M is, the more the glass forming ability. By calculation of the M, the glass forming ability of Al-based amorphous alloys could be predicted prior to the preparation for amorphous solids.更多还原