School of Materials Science and Engineering Dalian University of Technology

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12月9日学术报告通知
2016-12-07 13:56     (点击: )

时间:2016129日,10:00-11:40

地点:新三束实验室4号楼408

主办单位:材料学院磁性材料研究室

一、Tohru Yamasaki教授学术报告

题目:Development of Zr-Cu-Ni-Al Bulk Metallic Glasses with High Plastic Deformability and Application

报告人:Prof. Tohru Yamasaki,University of Hyogo, Japan

摘 要:

Zr55Cu30Ni5Al10(Zr55), Zr65Cu20Ni5Al10(Zr65) and Zr65+xCu17-xNi5Al10M3(Zr65+xM3, x = 0, 1.5 and 3 at.%, M= Au and Pd) bulk metallic glasses (BMGs) have been prepared by a tilt casting method. DSC results of the Zr65-BMG indicated the presence of a wide supercooled liquid region of 119 K between the glass transition temperature (Tg) of 644 K and the crystallization temperature (Tx) of 763 K. In contrast, by the Au/Pd addition BMGs, precipitation of an icosahedral quasicrystalline phase (I-phase) was observed in their supercooled liquid temperature regions. Compressive test was carried out at an initial strain rate of 5 x 10-4s-1at room temperature. By the Au/Pd additions, the yield stress was almost unchanged but the plastic strain at fracture was increased largely. The plastic strains at fracture of Zr55-, Zr65- and Zr65Au3/Pd3-BMGs were about 2 %, 10 % and more than 20 %, respectively. In the Zr66.5Au3/Pd3-BMGs, stress-increasing like a work hardening during plastic deformation was observed until more than 5% of compressive strain. By the transmission electron microscopy of the Au/Pd-addition BMGs, precipitation of nanocrystallites having about 5~10 nm in diameter was observed near the fractured surfaces of the compressive test specimens. So, the large increase of the plastic strain may be due to the work hardening by the dynamic precipitation of I-phase during plastic deformation. For industrial applications of Zr-based bulk metallic glasses with high yielding stress of about 1.5 GPa, nanoimprint moulding consisted of line and space structures with the interval of 700 nm and 300 nm was almost achieved successfully under the high moulding stress of about 2 GPa at room temperature.

主讲人简介:

Tohru Yamasaki(山崎徹)博士是日本兵库县立大学教授,微纳结构科学、先进医学工程研究中心主任,研究课题包括非晶及纳米晶材料的开发及其力学性能评价、液态合金的物理性质、非晶纳米晶合金的精密微成型工艺等。


二、Kazutaka Fujita教授学术报告

题目:Tensile Plastic Deformation of Zr-based Bulk Metallic Glasses

报告人:Prof. Kazutaka Fujita, National Institute of Technology, Ube College, Japan

摘 要:

Tensile tests on monolithic Zr-based Bulk metallic glass with high viscosity about more than 108Pa・sec were carried out to investigate the plastic deformation properties.

As the result, a plastic strain of about 0.3% with work hardening and following plastic strain of about 0.7% with serrations and work softening were shown on the stress-strain curves. Many shear bands on the large surface area of parallel part of the specimen were observed on the photographs by SEM and images by in-situ high speed video camera. Number of serrations corresponded well with number of the large shear bands.

It is presumed that not softening but hardening and serrations are induced by increasing viscosity in the shear bands due to initiation and growth of the quasicrystal cores during the plastic deformation.

主讲人简介:

Kazutaka Fujita(藤田和孝)博士是日本国立宇部工业高等学院教授,研究课题主要包括高强度高韧性块体金属玻璃、电解沉积纳米晶合金和生物机械复合电机等。

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