The effects of initial welding temperature and welding parameters on the crystallization behaviors of laser spot welded Zr-based bulk metallic glass

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Title:	The effects of initial welding temperature and welding parameters on the crystallization behaviors of laser spot welded Zr-based bulk metallic glass
Authors:	Wang,HS;Chiou,MS;Chen,HG;Jang,JSC
Contributors:	機械工程學系
Keywords:	NDYAG LASER;ALLOY;EVOLUTION;PHASE
Date:	2011
Issue Date:	2012-03-27 17:08:08 (UTC+8)
Publisher:	國立中央大學
Abstract:	This study investigated the effects of the initial welding temperature (IWT) and welding parameters on the crystallization behaviors of laser spot welded (Zr(53)Cu(30)Ni(9)Al(8))Si(0.5) bulk metallic glass (BMG). After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's micro-hardness test. The results showed that the heat-affected zone (HAZ) crystallization seemed avoidable under the room temperature welding process. However, with a combination of a lower energy input (welding Condition C) and a lower IWT (at 0 degrees C), a crystallization-free HAZ was finally obtained. Using the above welding condition into the refined heat flow equation, a critical retention time of 79 ms for the crystallization temperature interval was estimated. Moreover, as the laser welded samples came to crystallization in the HAZ, it was observed that a higher content of spherical-type crystalline precipitates tended to result in a higher value of glass transition temperature, T(g). Therefore, the GFA indices, Delta T(x), gamma and gamma(m), were reduced. Furthermore, it was found that the micro-hardness value in the HAZ crystallization area was decreased due to the massive cracks formed in most parts of the crystalline precipitates. For a crystallization-free HAZ, the hardness seemed unaffected. (C) 2011 Elsevier B.V. All rights reserved.
Relation:	MATERIALS CHEMISTRY AND PHYSICS
Appears in Collections:	[Departmant of Mechanical Engineering ] journal & Dissertation

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