Mixture of reactants for use in welding

An exothermic reaction mixture which upon initiation of an exothermic reaction forms a molten weld metal for use in joining one piece of aluminum or aluminum alloy with at least one other metal piece, said mixture of reactants comprising:

• about 20% to about 75% by weight aluminum;
• about 5% to about 50% by weight of a Group I metal sulfate;
• about 22% to about 50% by weight of a Group II metal sulfate;
• about 4% to about 20% by weight of at least one Group I metal fluoride;
• and
• about 0.1 to about 45% by weight silicon.

An exothermic reaction mixture which upon initiation of an exothermic reaction forms a molten weld metal for use in joining a non-ferrous metal piece with at least one other metal piece, said exothermic reaction mixture comprising:

• a reducing agent;
• a filler metal;
• one or more metallic compounds at least one of which is a Group I metal sulfate selected from the group consisting of sodium sulfate, lithium sulfate and potassium sulfate, which during said exothermic reaction are reduced by said reducing agent and form a compound with said reducing agent having a heat of formation which provides an exothermic reaction with sufficient heat to melt said filler metal;
• and
• at least one Group I metal fluoride flux selected from the group consisting of sodium fluoride, lithium fluoride, potassium fluoride, and sodium aluminum fluoride.