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Extract B

The unique properties of lasers account for their widespread application in manufacturing industry. Laser beam welding is currently used in order to weld steels, aluminum alloys and dissimilar materials. This high power density welding process has unique advantages of coast effectiveness, deep penetration and narrow bead in comparison with conventional welding processes. As the thermal cycles of laser beam welding are generally much faster than those of arc welding it is possible to form a rather small weld zone that exhibits locally high hardness.

However, it is important to point out that the metallurgical and mechanical properties of laser welds and the response of conventional materials to this new process have not been fully established yet. It is currently difficult to determine the tensile properties of the laser welded joint area owing to the small size (2-3 mm) of the fusion zone. Therefore an experimental investigation of the mechanical properties of laser-welded joints was carried out. To determine the hardness profile of the welded metal three similar joints were produced by a CO² laser and microhardness measurements were conducted at three locations. It is important to mention that the microhardness test results, however, exhibited no significant difference between these three locations for all the welded joints.

The welding process may lead to drastic changes in the microstructure with accompanying effects on the mechanical properties and, hence, on the performance of the joint. Laser welded joints, like all other welded joints, may contain defects in the form of cracks in the narrow weld area. The size and location of such cracks directly affect the joint performance and the lifetime of a structure. Nevertheless, it is essential to remember that laser beam welding has a number of advantages over conventional processes. Despite the high investment cost of laser welding equipment, it is expected that laser beam welding will have a great impact on fabrication and manufacturing industries within the next decade.

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