LASER WELDING OF Ni_3Al INTERMETALLIC COMPUNDS FOILS

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We studied laser welding properties of cold-rolled Ni_3Al foils which we for the first time successfully developed.1.Recrystallization behavior of cold-rolled Ni_3Al foils and improvement of the mechanical properties.We discovered a new phenomenon named texture memory effect in our heavily cold-rolled Ni_3Al foils : the recrystallization texture return to the original cold-rolled texture during grain growth. We found that the fraction of ductile boundaries, Σ1, Σ3, and Σ9, increases during grain growth, resulting in the large tensile elongation of about 10%.2.Laser spot welding of Ni_3Al foilsSolidification cracking occurs in the fusion zone in the case of cold-rolled foils. The cracks do not propagation far beyond the shrinkage hole of the fusion zone in the 30 μm-thick foils. In contrast they propagate through the heat-affected-zone to the base metal in the 100 μm-thick foils, but the crack propagation can be effectively suppressed by preheating with continuous wave laser, probably because of reduction of thermal stress.Solidification cracking does not occur in the case of recrystallized foils. It is because thermal stress is relaxed due to plastic deformation in the heat-affected zone.It is thus concluded that good laser spot welding is achievable for both cold-rolled and recrystallized foils.3.Laser seam welding of Ni_3Al foilsWe investigated the seam welding behavior of both cold-rolled and recrystallized foils by using direct diode laser. Transverse cracking occurs for the cold-rolled foils thicker than 200 Km, while not for the foils thinner than 100 Km because of low thermal stress generated. The latter goes for the recrystallized foils.We thus revealed the laser spot and seam welding behaviors of Ni_3Al foils and good welding conditions without weld cracking.