A method for forming a weld joint, comprising: - melting at least a portion of a work piece base metal while adding a filler metal to form the weld joint, wherein the filler metal is an Al-Si-Mg alloy consisting of: - 5.0 to 6.0 wt % silicon; - 0.31 to 0.5 wt % magnesium; and - the balance being aluminium and trace elements, wherein the trace elements consist of: - a maximum allowable amount of iron of 0.8 wt %; - a maximum allowable amount of copper of 0.3 wt %; - a maximum allowable amount of manganese of 0.05 wt %; - a maximum allowable amount of zinc of 0.2 wt %; - a maximum allowable amount of titanium of 0.2 wt %; - a maximum allowable amount of beryllium of 0.0003 wt %; and - other trace elements are allowable in a maximum weight percent of 0.05% each, the other trace elements together being allowable in a maximum weight percent of 0.15% total, characterized by further comprising a heat treating step with a temperature in a range of 590.6 °C (1095 °F) and 615.6 °C (1140 °F), wherein said other trace elements comprising zirconium, scandium and/or chromium. - melting at least a portion of a work piece base metal while adding a filler metal to form the weld joint, wherein the filler metal is an Al-Si-Mg alloy consisting of: - 5.0 to 6.0 wt % silicon; - 0.31 to 0.5 wt % magnesium; and - the balance being aluminium and trace elements, wherein the trace elements consist of: - a maximum allowable amount of iron of 0.8 wt %; - a maximum allowable amount of copper of 0.3 wt %; - a maximum allowable amount of manganese of 0.05 wt %; - a maximum allowable amount of zinc of 0.2 wt %; - a maximum allowable amount of titanium of 0.2 wt %; - a maximum allowable amount of beryllium of 0.0003 wt %; and - other trace elements are allowable in a maximum weight percent of 0.05% each, the other trace elements together being allowable in a maximum weight percent of 0.15% total, characterized by - 5.0 to 6.0 wt % silicon; - 0.31 to 0.5 wt % magnesium; and - the balance being aluminium and trace elements, wherein the trace elements consist of: - a maximum allowable amount of iron of 0.8 wt %; - a maximum allowable amount of copper of 0.3 wt %; - a maximum allowable amount of manganese of 0.05 wt %; - a maximum allowable amount of zinc of 0.2 wt %; - a maximum allowable amount of titanium of 0.2 wt %; - a maximum allowable amount of beryllium of 0.0003 wt %; and - other trace elements are allowable in a maximum weight percent of 0.05% each, the other trace elements together being allowable in a maximum weight percent of 0.15% total, characterized by - a maximum allowable amount of iron of 0.8 wt %; - a maximum allowable amount of copper of 0.3 wt %; - a maximum allowable amount of manganese of 0.05 wt %; - a maximum allowable amount of zinc of 0.2 wt %; - a maximum allowable amount of titanium of 0.2 wt %; - a maximum allowable amount of beryllium of 0.0003 wt %; and - other trace elements are allowable in a maximum weight percent of 0.05% each, the other trace elements together being allowable in a maximum weight percent of 0.15% total, further comprising a heat treating step with a temperature in a range of 590.6 °C (1095 °F) and 615.6 °C (1140 °F), wherein said other trace elements comprising zirconium, scandium and/or chromium.