標題: A study of weldability and fracture modes in electron beam weldments of AZ series magnesium alloys
作者: Chi, Chao-Ting
Chao, Chuen-Guang
Liu, Tzeng-Feng
Wang, Che-Chung
材料科學與工程學系
Department of Materials Science and Engineering
關鍵字: electron beam welding;weldability;process window;fracture mode
公開日期: 5-Nov-2006
摘要: Given the growing need for environmental protection and lightweight construction, electron beam welding (EBW) is becoming the most important welding technology because it can compensate for the poor formability of magnesium alloys. This paper examines interactions between the properties of three AZ series magnesium alloys and welding conditions. The EBW process can yield four kinds of defect in a weld: cavities, the heat-affected zone (HAZ), undercuts, and root concavities. These defects obviously induce stress concentrations in the weld, and may seriously damage its strength. Additionally, the distribution of precipitates (gamma phase, Mg17Al12) in the fusion zone (FZ) changes from a relatively small number of scattered particles to a dense population of dendrites as the Al content of the magnesium alloy increases. Under excessive tensile stress, alloy weldments break in one of two fracture modes: an irregular FZ fracture, or a regular HAZ fracture. AZ31B usually exhibits the former mode and AZ91D the latter, while AZ61A exhibits each mode half the time. The overall weldability, which depends on the random distribution of these precipitates and defects, is found to be greatest for the AZ61A alloy. The best process window, on the other hand, is found for the AZ91D alloy. Finally, we obtain optimum parameters for the EBW process and empirical formulae for the weldment strength as a function of these parameters. These results are closely related to each other. (c) 2006 Elsevier B.V. All rights reserved.
URI: http://dx.doi.org/10.1016/j.msea.2006.07.098
http://hdl.handle.net/11536/11560
ISSN: 0921-5093
DOI: 10.1016/j.msea.2006.07.098
期刊: MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume: 435
Issue: 
起始頁: 672
結束頁: 680
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