Beryllium copper

Beryllium copper is a high-strength, highly conductive material, but welding is tricky. The problem is its tendency to hot cracking if you put in too much heat or don't control cooling properly. You have to keep heat low and work quickly so the material doesn't overage and become brittle. After welding, controlled aging is important to restore original strength. If you work unclean, the part will crack or you'll lose the required mechanical properties.