X-ray Study on Plastic Strain Distribution in Soft Zone of A5052-H Weld Metal

Abstract

In ship yards, for example, they prefer to use work-hardened aluminum sheets instead of annealed sheets for weld structural materials of ships because of the easiness of handling them. When we perform fusion welding on the work-hardened aluminum sheets soft zone is developed near weld metal. This zone influences mechanical properties of weld joints. In this study the authors examined plastic strain distribution in the soft zone by applying X-ray diffraction technique. The plastic strain was estimated by integral breadth of X-ray diffraction intensity curve. Since we need some area for irradiating X-rays we study the appropriate irradiation width by simulating the plastic strain distribution by considering the influence of the irradiation width. The result shows that the irradiation width does not influence the plastic strain distribution when we perform correction proposed in this study but the important point is to use the appropriate distance shifted in irradiation and 1 or 2 mm is appropriate. The plastic strain has the value of 0% near fusion boundary, increases abruptly into heat-affected-zone and reaches the value of the work-hardened (about 13%). The width of the soft zone depends on weld heat input. The larger the heat input, the wider the width. By examining the temperature distribution during welding, plastic strain tends to decrease when the material is heated higher than about 300°c and to be zero percent higher than about 450°C (this temperature depends on the welding speed, and the higher the welding speed the higher the temperature). When we measure the area surrounded by a curve of welding thermal cycle and the temperature of 300°C the value of about 108°Cs is obtained for every welding speed when plastic strain decreases to zero.