ANALISIS SIFAT MEKANIK HASIL PENGELASAN ALUMINIUM AA 1100 DENGAN METODE FRICTION STIR WELDING (FSW)

Abstract

Development of the industrial world are now starting to consider the aluminum material as the main ingredient in the production process. This is because aluminum and aluminum alloys including light metals having high strength, corrosion resistance, good electrical conductors and aluminum is lighter than iron or steel. The use of aluminum in particular types of AA 1100 in the industrial world are widely used for heat exchangers, pressure vessels, pipes, etc. However, aluminum and aluminum alloys have properties that are less well when compared to steel, such as specific heat and has a high conductivity, easily oxidized and forming an aluminum oxide Al2O3 having a high melting point, resulting in a fusion between the base metal and weld metal to be blocked and if in too fast cooling process will form a smooth cavity ex-pouch of hydrogen. However, the most fundamental difference is the value of perseverance in the weld metal, where the value of steel weld metal toughness is always high when compared with the parent metal, while in the weld metal toughness values of aluminum tend to be smaller than the value of toughness in the parent metal. Along with these case need to be done research to makes it easy of aluminum welding and have optimal strength. One of which the welding process of aluminum alloy can be done by friction stir welding. FSW (friction stir welding) is a welding method that has been discovered and developed by Wayne Thomas for the work piece of aluminum and aluminum alloy in 1991 at TWI (The Welding Institute) United States. FSW welding process to occur in the solid state (solid state joining). FSW welding process to occur at the solvus temperature, so there is no decrease in strength due to overaging and dissolving of x the precipitate coherent. Because the welding temperature is not too high, then the residual stress and distortion of heat effect is also low. Mechanical characteristics of the FSW is determined by the parameters: welding speed, tool rotation and tool pressure. In this research, the welding of aluminum AA 1100 by friction stir welding method (FSW) can be done well. Tensile test results obtained that the averages of ultimate strength for welding with using 780 rpm is 52 222 Mpa, for 980 rpm is 38 472 MPa and 1120 rpm is 56 528 MPa. With these results can be seen that the highest ultimate strength is use 1120 rpm and ultimate strength at 980 rpm is the lowest. Wormholes defects in the welding with 980 rpm is the main factor that reduces the tensile strength in this research. Macro observations are known the largest wormholes defects in the welding with 980 rpm and also the presence of cracks due to lack of penetration and cause of stress concentration at the weld, this case also occurs at 780 rpm. From micro observations is known on the grains shape of the stir zone, FeAl3 particles is spread more evenly in matrix of Al due to the stir process during the welding process. Hardness testing showed that the weld metal is softer than the parent metal. While the TMAZ region has the lowest hardness.