The butt joints of semi solid 356 were produced in as cast conditions by friction stir
welding process (FSW). This experiment studied in pre/post heat treatment (T6) using the welding
speed 160 mm / min with tilt angle tool at
3 degree and straight cylindrical tool pin. The factors of
welding were rotating speed rates at 1320, 1750 rpm and heat treatment conditions. They were
divided into (1) As welded (AW) joints, (2) T6 Weld (TW) joints, (3) Weld T6 (WT) joints, (4) T6
Weld T6 (TWT) joints, (5) Solution treated Weld Artificially aged (SWA) joints and (6) Weld
Artificially aged (WA) joints. Rotating speed and heat treatment (T6) condition were an important
factor to micro, macro structure of metal and mechanical properties of the weld. Increasing rotating
speed and different heat treatment condition impacted onto tensile strength due to the defects on
joints. Therefore the optimum welding parameter on joint was a rotating speed 1320 rpm, the
welding speed 160 mm/min, heat treatment condition of Weld T6 (WT) which obtained the highest
tensile strength 228.92 MPa, as well as, highest hardness of 98.1 HV