Effect of Laser Welding Parameters on Porosity of Welds in Cast Magnesium Alloy AM50
Journal Title: Modern Approaches on Material Science - Year 2018, Vol 1, Issue 2
Abstract
Magnesium alloys are light-weight metals suitable for applications in several industries, such as automotive and aerospace. Compared with most materials they provide a possibility to reduce weight due to their high specific strength. However, their tensile strength is low (190-310MPa) compared with steels, which may limit their application; for example, to car interior parts such as seat frames, steering wheels or structural dashboard cross beams [1-4]. A common magnesium alloy is AM50 (4.4-5.5 wt% Al, 0.26-0.6 wt% Mn) which, compared with other magnesium alloys, is of relatively high strength, high hardness, high elongation and has excellent castability. Often magnesium alloys are cast into complex shapes using high pressure die-casting [5-8]. An alternative is to cast less complicated parts and join them by welding, commonly by tungsten inert gas (TIG) or metal inert gas (MIG) welding [2]. An alternative is laser welding, where high power densities are attained with small welding spots, allowing relatively high welding speed and low heat inputs to be achieved. Low heat input is an advantage for many metallic materials as a narrow fusion zone and HAZ will form, reducing negative effects on material properties [2]. Laser welding of magnesium alloys was reviewed by [9], who stated that crack-free laser welds with low porosity and good surface quality could be obtained when using appropriate welding parameters. Nevertheless, magnesium alloys may exhibit many processing problems and weld discontinuities, such as an unstable weld pool, spatter, drop-through, sagging, undercut, porosity, cracking, and oxide inclusions. Pores in the weld metal lower especially the tensile strength and may have a deleterious effect on fatigue performance if surface breaking. Therefore, it is important to understand the pore formation mechanisms and find procedures that could be used to reduce pore formation [2,10]. Porosity in welded magnesium alloys has been the subject of a number of previous investigations [2,10-15]. In these studies, a range of different factors have been found to cause pore formation including: hydrogen, an unstable keyhole, pre-existing pores from the die-cast process, surface condition, gas entrapment.
Authors and Affiliations
Karl Fahlström, Jon Blackburn, Leif Karlsson, Lars-Erik Svensson
Keywords
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- EP ID EP576525
- DOI 10.32474/MAMS.2018.01.000106
- Views 51
- Downloads 0
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