文档介绍：Materials Characterization 52 (2004) 49–64
Microstructures in friction-stir welded dissimilar magnesium alloys
and magnesium alloys to 6061-T6 aluminum alloy
. Somasekharan, . Murr*
Department of Metallurgical and Materials Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA
Received 9 September 2003; accepted 10 March 2004
Abstract
Wrought Mg alloy AZ31B-H24 and semisolid-cast Mg alloy AZ91D (approximately 3% primary solid fraction) were
friction-stir welded to Al alloy 6061-T6. Semisolid-cast (approximately 3% and approximately 20% primary solid fractions) Mg
alloys AZ91D and AM60B were also joined using the same technique, with AZ91D on the advancing side. Numerous welds
were made with the Mg alloys and the 6061-T6 Al alloy in alternating advancing and retreating sides. Light optical
metallography was used to observe and confirm the weld zone characteristics unique to dissimilar welds. Dynamic
recrystallization (DRX) was observed in the weld region as well as in the transition region, with a clear decrease in the grain size
from the base material through the transition zone and into the weld zone. The welds were free of porosities. The welds between
the dissimilar Mg alloys revealed a homogeneous, equiaxed, fine-grained structure in the weld zone. The weld zone in the welds
of the Mg alloys to Al alloy 6061-T6 showed unique dissimilar weld, flow characteristics, such plex intercalated
microstructures with recrystallized lamellar-like shear bands rich in either Mg or Al. Elemental analysis performed on the weld
region showed bands with equal parts of Mg and Al, as well as unique recrystallized bands with a predominance of either
material. Vickers microhardness testing on all the welds revealed a lack of degradation of residual microhardness of the
materials in the weld zone or the transition zone, with some unusual, erratic hardness spikes exhibiting hardness values as much
as three times that of the base material