equipped with an EDS. As shown in Fig. 2B, 5-mm-wide rectangular shaped specimens were cut from the brazed joints and subjected to tensileshear tests with a crosshead speed of 1 mm/min. Shims were used at each end of the specimens to ensure shear loads in the lap joint while minimizing induced couples or bending of the specimens. Average tensile shear strength was calculated from tensile specimens to estimate the static mechanical resistance and joint efficiencies of the joints. Results A photograph of a laser-brazed Ni electroplated steel/AZ31B joint and a typical cross-sectional view of the joint are shown in Fig. 3. This brazed joint was made using 2.2 kW laser power, 8 mm/s travel speed, and 0.2 mm beam offset to the steel side. B The joint exhibited a uniform brazed area with good wetting of both base materials. Partial melting of the AZ31B base metal was observed. In contrast, when bare steel was used, no bonding occurred between the steel sheet and the braze alloy fusion zone (FZ) and wetting of the steel by the braze metal was very poor (Ref. 15). The 5.5-μm-thick Ni electrodeposited layer on the surface of the steel significantly improved the wetting of the steel by molten JANUARY 2013, VOL. 92 4-s WELDING RESEARCH Fig. 4 — Transverse sections of a laser brazed joint. A — Optical micrograph of the entire joint and SEM images in different positions along the steel-FZ interface; B — position A; C — position C; D — position E; E — position F. Fig. 5 — Typical temperature vs. time profiles measured during laser brazing at the top and bottom side of the joint. A C E D
Welding Journal | January 2013
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