Keywords : Welding Defects
USING FRICTION STIR PROCESS (FSP) TO IMPROVE THE PROPERTIES OF AA7020 ALUMINUM ALLOY WELDMENTS WELDED BY TUNGSTEN INERT GAS (TIG).
journal of kerbala university,
Volume 11, Issue 1, Pages 50-60
One technique that may be used for repair of defects arising from process upsets is simply re-welding using the nominal process parameters. In such a case, it is important to know whether or not using a different welding process is capable of repairing defects in the already welded material (which will presumably have somewhat different properties as compared to the base metal). To examine this issue , three TIG weld passes were performed in aluminum AA7020 strips(6 piers of strips with 25 *200 *9.5 mm dimension ) by used (Al Mg 5 Cr ) filler metal according to AWS (A- 5.10) standard .Then friction stir weld pass were performed in exiting TIG welds (for only 3 piers of welded strips) with a tool rotation speed of (1000 rpm) and moved straight speed (welding speed ) of (14 m /min). Microstructure and Vickers hardness testes were done for weldments in three regions (base metal , TIG and FSP weld metals) to comparison .
Results indicate that for this material and these conditions weld control parameters its possible to use another welding process to reduce defects in upsets process. Weld metallurgy is only slightly changed in the interface between TIG and FSP structures due to refining in exiting TIG welds structures. While there is no change in metallurgy of other TIG passes and base metal. Hardness in the weld metal after FSP pass increased by about 120% of the base metal.