Joining of (Zr53Cu30Ni9Al8)Si0.5 Bulk Metallic Glass Using Pulsed Nd:YAG Laser Welding

• Main Authors: Chung-chun Hsueh, 薛仲俊
• Other Authors: Huei-sen Wang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/22030736129658327355

碩士 === 義守大學 === 材料科學與工程學系碩士班 === 97 === The study applies the technology of Nd:YAG Pulse Laser Welding that could speed up Welding Thermal Cycle to operate in coordination with various welding parameters to practice laser welding experiments on (Zr53Cu30Ni9Al8)99.5Si0.5 BMG test chips so as to conquer the common quandary of bulk metallic glass crystallization during welding. The study applies multiple different Nd:YAG laser welding parameters to practice welding on (Zr53Cu30Ni9Al8)99.5Si0.5 BMG during the experiment in room temperature and under the influence of LN2. We observe the micro-structure and crystallization phenomenon on the welding path and Heat Affected Zone(HAZ) after welding by sorts of equipment such as OM, TEM, SEM, EDS and XRD. By comparing all sorts of data such as microcosm, mechanical property, chemical composition, and thermal properties, we understand the actual influence of welding on the mechanical property and thermal properties and the crystallization phenomenon appeared afterwards. The study conclusion reveals that there are 2 different types of heat affected zone appeared aside from the welding path after applying Nd:YAG pulse laser welding, which is located on serious melting heat affected zone(HAZ) on the welding path and the material itself. The study selects 3 welding parameters to perform on (Zr53Cu30Ni9Al8)99.5Si0.5 BMG in room temperature. The welding path did reach the non-crystallization condition, but the crystallization appears on the Heat Affected Zone, mainly on the central part of the Heat Affected Zone on the test chips. We deduce the conclusion that maintaining for a long time in the crystallizing temperature leads the central area to precipitate crystal particles. The Heat Affected Zone surface on the test chips did not appear crystallization phenomenon. This could be inferred to the protection gas(Ar) accelerate the cooling speed. In the condition when apply LN2 in the experiment, both the welding path and HAZ will meet the criteria of non-crystallizing. The crystal particles produced during the experiment is proved to be Zr2Cu by TEM. The size of the particle ranges from 30nm to 200nm. It is also discovered that once when the crystal particle reaches more than 50nm, the possibility of fracture increases; but when the size below 30-50 nm, there will be no fracture. Inferring by the data gathered from the Micro-hardness test, the micro hardness in the Heat Affected Zone and the central area of welding path of the test chips appear substantial difference after Nd:YAG pulse laser welding. The phenomenon could be inferred to the crystallization produced during the welding on the Heat Affected Zone that results in a certain degree influence on the crystal particle density. By synthesizing experiment results, we could gain more understanding on the crystallization mechanism showing on the (Zr53Cu30Ni9Al8)99.5Si0.5 after Nd:YAG pulse Laser Welding. The study conclusion could be applied in the (Zr53Cu30Ni9Al8)99.5Si0.5 welding procedure.