ANALISIS PENGARUH VARIASI TEMPERATUR PREHEAT PADA PENGELASAN GTAW ALUMINIUM 6061 TERHADAP SIFAT MEKANIK DAN STRUKTUR MIKRO

Aluminum 6061 is included in the heat treatable aluminum alloy, during the welding process deformation, cracks, porosity or other welding defects will usually occur which results in a change in the metallurgical composition of the aluminum material resulting in reduced material strength. In this research the variations used are non preheat, preheat 80°C and preheat 120°C. The results of the tensile test with the highest tensile strength value of 189.08 MPa at 120°C preheat variation, then the presence of higher preheat can increase the tensile strength of the material. Micro test results show that the higher the preheat temperature will cause the precipitate to be dispersed, thereby reducing the precipitate content which can affect the mechanical properties of the material. The results of the hardness test, the higher the preheat temperature, the lower the hardness of the material, this can also be seen from the differences in the shape of the microstructure. However, in the welding process with 80°C and 120°C preheat, it was seen that the hardness value in the weld metal increased beyond the hardness in the base metal area which could be caused by a hardening of the precipitate. The highest hardness test result was 67.68 HV on the non-preheat base metal and the lowest hardness was 56.17 HV on the preheat base metal at 120°C