In the present study, butt joints of aluminum (Al) 8011-H18 and pure copper (Cu) were produced by friction stir welding (FSW) and the effect of plunge depth on surface morphology, microstructure and mechanical properties were investigated. The welds were produced by varying the plunge depth in a range from 0.1 mm to 0.25 mm. The defect-free joints were obtained when the Cu plate was fixed at the advancing side. It was found that less plunging depth gives better tensile properties compare to higher plunging depth because at higher plunging depth local thinning occurs at the welded region. Good tensile properties were achieved at plunge depth of 0.2 mm and the tensile strength was found to be higher than the strength of the Al (weaker of the two base metals). Microstructure study revealed that the metal close to copper side in the Nugget Zone (NZ) possessed lamellar alternating structure. However, mixed structure of Cu and Al existed in the aluminum side of NZ. Higher microhardness values were witnessed at the joint interfaces resulting from plastic deformation and the presence of intermetallics.

The gas porosity is one of the most serious problems in the casting of aluminum. There are several degassing methods that have been

studied. During smelting of aluminum, the intermetallic compound (IMC) may be formed at the interface between molten aluminum and

solid steel of crucible furnace lining. In this study, the effect of degassing treatment on the formations of IMC has been investigated. The

rectangular substrate specimens were immersed in a molten aluminum bath. The holding times of the substrate immersions were in the

range from 300 s to 1500 s. Two degassing treatments, argon degassing and hexachloroethane tablet degassing, were conducted to

investigate their effect on the IMC formation. The IMC was examined under scanning electron microscope with EDX attachment. The

thickness of the IMC layer increased with increasing immersion time for all treatments. Due to the high content of hydrogen, substrate

specimens immersed in molten aluminum without degasser had IMC layer which was thicker than others. Argon degassing treatment was

more effective than tablet degassing to reduce the IMC growth. Furthermore, the hard and brittle phase of IMC, FeAl3, was formed

dominantly in specimens immersed for 900 s without degasser while in argon and tablet degasser specimens, it was formed partially.