Tensile rheological behavior of the Zr35Ti30Be27.5Cu7.5 metallic glass under conditions of high strain rates (strain rates ranging from 0.05 s-1 to 0.5 s- 1) within the supercooled liquid region was studied. The stress -strain curve reveals that this metallic glass demonstrates non -Newtonian flow characteristics under these circumstances. The peak stress associated with stress overshoot increases as temperature decreases and strain rate increases. However, the steady-state flow stress displays an anomalous decrease due to rapid necking at high strain rates. Subsequently, the thermal processing map of the Zr35Ti30Be27.5Cu7.5 metallic glass was established and analyzed. It reveals that the alloy has relatively excellent thermoplastic forming ability at temperature between 630 K and 655 K and strain rates between 0.05 s-1-0.2 s-1. We found that under strain rates epsilon >= 10-2 s-1, the strain rate is the primary factor influencing normalized viscosity. Therefore, we developed a simplified Maxwell -Pulse constitutive model applicable to metallic glass in the supercooled liquid region under high strain rate conditions, by simplifying the constitutive equation for steady-state flow stress using a simplified formula for normalized viscosity calculation. The predictions of this simplified modified model align well with experimental values. By comparing the simplified and unsimplified Maxwell -Pulse constitutive models, the overall fitting accuracy of the simplified model was improved by 3-5%, with the highest improvement of 67% in the steadystate flow stress stage. These results indicate that the modified model accurately reflects the stress -strain relationship for the Zr35Ti30Be27.5Cu7.5 metallic glass under high temperature and high strain rate tensile conditions.

The bulk Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 amorphous alloy was prepared by copper mold suction casting. The effects of two size factors, diameter and aspect ratio, on the compression deformation behavior of the amorphous alloy were studied by room temperature compression experiments. The results show that the amorphous alloy has size effect, that is, with the increase of height diameter ratio and diameter, the internal stress loading mode and shear band density change. The inner shear band of the specimen with small diameter to height diameter ratio is more dense, which can realize the stable expansion of the shear band and thus present higher plasticity. The yield strength is little affected by the size factor and almost remains unchanged. The experiment integrates many aspects of knowledge such as material preparation and characterization, which is conducive to students’ understanding of basic knowledge, training of scientific research thinking, logical reasoning and multifactor thinking ability, and facilitating their access to knowledge in the frontier field of new materials.

在非晶合金中添加第二相制备非晶合金复合材料能够有效地解决非晶合金室温脆性的问题,但第二相的引入对非晶基体高温变形行为造成的影响尚不明确.本研究在Zr55Cu30Al10Ni5非晶合金中添加两种不同的陶瓷颗粒Al2O3和Si3N4,通过放电等离子烧结法制备了一系列不同体积分数的陶瓷颗粒增强Zr基非晶合金复合材料.通过进行高温压缩试验,并建立多颗粒随机分布模型进行数值模拟,对其高温变形行为进行了系统性研究.结果表明,在421℃时,两种复合材料都表现为应力过冲后应变硬化;在441℃时,Al2O3增强的复合材料表现为屈服后应变硬化,对于SisN4增强复合材料,当第二相体积分数小于25％时表现为屈服后应变硬化,当第二相体积分数大于25％时材料却表现为应力过冲后应变硬化.两种非晶合金复合材料的高温变形行为差异与增强相形貌以及增强相颗粒团聚行为导致的第二相分布不均匀有关.

The 17CrNi2MoVNb alloy is widely used for manufacturing heavy-duty gears in vehicles’ transmission systems, where grinding is a significant process affecting gears’ working performance and service life. This work comprehensively analyzed the grinding force, surface morphology, and surface roughness when grinding 17CrNi2MoVNb alloy using alumina and CBN grinding wheels. Results showed that the maximum normal grinding force from the CBN wheel was only ~67% of the one from the alumina wheel. Due to the small size and limited cutting depth of CBN grains, the grinding force increased by about 20% when the grinding depth increased from 0.02 to 0.03 mm for CBN grinding wheels. Surface defects, including cavities and material tearing, were mainly found on the ground surface when using an alumina grinding wheel. The surface roughness Ra recorded from the CBN grinding wheel mainly ranged from 0.263 to 0.410 μm, accounting for less than 40% of the one from the alumina grinding wheel. The information from this work could provide benchmark data and references for optimizing grinding tools and parameters when manufacturing gears in the vehicle industry.