An insight to the mechanism of weld penetration in dissimilar pulsed laser welding of niobium and Ti–6Al–4V

• In dissimilar laser welding of Ti–6Al–4V/Nb signs of dissolution are observable.
• Locating 60% of laser beam diameter on Ti alloy results to full penetration welding.
• Energy absorbed by keyhole formed on Ti–6Al–4V will help in melting of Nb wall.
• Flowing molten material in common weld pool promotes niobium wall dissolution.

In laser welding of Ti–6Al–4V to niobium, the interaction of laser with the two metals is such that at the investigated laser conditions there will be conduction mode on the Nb side and keyhole on the Ti side. Thus the weld pool is not developed symmetrically as there will not be sufficient penetration in the higher melting point higher conductivity niobium side. The mechanisms of energy absorption and effective melting in dissimilar laser welding are analyzed. It is shown that more penetration into niobium is obtained when the laser energy is absorbed by Ti–6Al–4V and then the molten Ti–6Al–4V dissolves the niobium metal.