A composition for welding or brazing aluminum comprises silicon (Si) and magnesium (Mg) along with aluminum in an alloy suitable for use in welding and brazing. The Si content may vary between approximately 4.7 and 10.9 wt %, and the Mg content may vary between approximately 0.20 wt % and 0.50 wt %. The alloy is well suited for operations in which little or no dilution from the base metal affects the Si and/or Mg content of the filler metal. The Si content promotes fluidity and avoids stress concentrations and cracking The Mg content provides enhanced strength. Resulting joints may have a strength at least equal to that of the base metal with little or no dilution (e.g., draw of Mg). The joints may be both heat treated and artificially aged or naturally aged.