预压缩处理及元素掺杂对锆基非晶合金室温塑性的影响

发布时间：2018-06-05 04:12

本文选题：非晶合金 + 预压缩处理　；参考：《兰州理工大学》2017年硕士论文

【摘要】：由于非晶体金属材料具有特殊的组织结构,其原子在三维空间中呈现出短程有序而长程无序的混乱排列,因此具备一些优于晶体金属材料的物理及化学性能,如高强度、低弹性模量及良好的耐腐蚀性能等,凭借这些优点,此类材料受到国内外研究学者的广泛关注。但也正是这种特殊的原子排列方式,使得非晶体金属材料具有较差的室温塑性,脆性断裂的破坏方式限制了其在工程上的应用。微小的形变加工及元素掺杂能够在一定程度上使非晶合金的室温塑性得到提升。因此,本文基于Zr基非晶合金的研究现状,选取了非晶形成能力好,但室温塑性差的Cu_(36)Zr_(48)Al_8Ag_8为研究对象,对其进行微小弹性预压处理及添加合金化元素Ni和Nb,探究这两种方式对Cu_(36)Zr_(48)Al_8Ag_8非晶合金室温塑性的影响。其中微小弹性预压处理的具体过程为:对非晶合金试样施加低于其屈服载荷的压应力,使试样仅发生线弹性或滞弹性变形,卸载后无宏观永久变形。在此基础上研究不同方式的预压工艺参数(不同压力、保压时间及循环次数)的影响权重,确定最佳工艺,并采用此种工艺参数为实验手段,通过差示扫描量热分析(DSC)非晶合金增塑的具体微观机理;元素掺杂的具体过程为:采用铜模吸铸技术制备出一系列直径为3 mm的(Cu_(0.36)Zr_(0.48)Al_(0.08)Ag_(0.08))100-x Nix(x=0、2、4、6)及(Cu_(0.36)Zr_(0.48)Al_(0.08)Ag_(0.08))100-x Nbx(x=0、1、2、4)棒状试样,使用X射线衍射仪(XRD)、透射电子显微镜(TEM)及扫描电子显微镜(SEM)对元素掺杂后的试样进行微观组织结构分析,确定元素掺杂对非晶合金室温塑性影响的原因。两者实验方法的力学性能均通过万能力学试验机进行测定。研究结果表明:(1)Cu_(36)Zr_(48)Al_8Ag_8非晶合金试样在经过预压缩处理后,室温塑性均产生了相应的变化,确定了最佳的工艺参数,并得出循环次数对试样室温塑性的变化影响最大,保压时间次之,而压力对试样室温塑性的变化影响较小;(2)Cu_(36)Zr_(48)Al_8Ag_8非晶合金试样内自由体积的含量随保压时间的变化而变化且剪切带的扩展及增殖方式也与自由体积的含量成正比例关系;(3)适量Ni元素的添加促进了试样的相分离程度,产生小尺寸晶体相,改善试样的室温塑性;(4)适量Nb元素的添加能够促进B2-Cu Zr增韧相的析出,并抑制其发生共析分解,改善试样的室温塑性。
[Abstract]:Because of the special structure of amorphous metal materials, the atoms of amorphous metal materials exhibit short range ordered and long range disordered arrangement in three dimensional space, so they have some better physical and chemical properties than crystal metal materials, such as high strength. With the advantages of low modulus of elasticity and good corrosion resistance, this kind of material has been widely concerned by researchers at home and abroad. However, it is precisely this special arrangement of atoms that makes amorphous metal materials have poor room temperature plasticity, and the failure mode of brittle fracture restricts their application in engineering. The room temperature ductility of amorphous alloys can be improved to a certain extent by micro deformation processing and element doping. Therefore, based on the current research situation of Zr-based amorphous alloys, Cu_(36)Zr_(48)Al_8Ag_8 with good amorphous forming ability but poor room temperature plasticity is selected as the research object. Micro elastic preloading and adding alloying elements Ni and NB were carried out to investigate the effect of these two methods on the room temperature plasticity of Cu_(36)Zr_(48)Al_8Ag_8 amorphous alloys. The specific process of micro-elastic preloading is that the specimen is subjected to compressive stress lower than its yield load, so that only linear elastic or anelastic deformation occurs, and no macroscopic permanent deformation occurs after unloading. On this basis, the influence weight of different preloading process parameters (different pressure, pressure holding time and cycle times) was studied, and the optimum process was determined, and the process parameters were used as experimental means. By differential scanning calorimetry (DSC), the specific microcosmic mechanism of plasticization of amorphous alloys was analyzed. The specific process of element doping was as follows: a series of copper mould suction casting technique was used to prepare a series of corrugated samples with a diameter of 3 mm. A series of Cupperton 0.36Nixx02446) rod specimens were prepared. X-ray diffractometer (XRD), transmission electron microscopy (TEM) and scanning electron microscope (SEM) were used to analyze the microstructure of the doped samples, and to determine the reasons for the effect of doping on the ductility of amorphous alloys at room temperature. The mechanical properties of both methods were measured by universal mechanical testing machine. The results show that after precompression treatment, the plastic properties of the amorphous alloy samples have changed at room temperature, and the optimum technological parameters have been determined. The results show that the cyclic times have the greatest influence on the room temperature plasticity of the samples, and the holding time is the second. The effect of pressure on the plasticity at room temperature is relatively small, and the free volume content in the sample varies with the holding time, and the expansion and propagation mode of the shear band is proportional to the free volume content. The addition of appropriate amount of Ni promoted the phase separation of the sample. The addition of appropriate NB element can promote the precipitation of B2-Cu Zr toughened phase, restrain the eutectoid decomposition, and improve the room temperature plasticity of the sample.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG139.8;TG306

【参考文献】