Investigation of the effects of SR additions on microstructure and mechanical properties of alloy in AlSi12(Fe) high-pressure die casting alloy

Aluminium and its alloys have become one of the most widely used engineering materials due to meeting the weight reduction and higher strength targets of the automotive sector more particularly in critical applications. In this thesis; changes in microstructure and mechanical properties of AlSi12(Fe) high pressure die casting (HPDC) alloy based on Si modification via different amounts of Sr were investigated. Mould filling and solidification analyses of the AlSi12(Fe) HPDC alloy were carried out with the help of MagmaSoft and Click2Cast software. The simulation parameters and injection press parameters that were chosen used during casting were used the same to compare casted product versus simulation casting process results on the simulation programs. Since one of the main subjects of the study is to determine the effects of increased Sr amount on the mechanical properties of AlSi12(Fe) alloy. Therefore, five different castings were organized for five different Sr parameters as 0 ppm, 20 ppm, 40 ppm, 80 ppm, and 160 ppm respectively. The metal quality was determined depending on the increasing Sr content of the alloy by obtaining and characterizing the RPT samples simultaneously with the casting studies. In order to determine the metal quality, RPT samples were subjected to metallographic preparation processes. The metal quality was determined after the surface analyzes of RPT samples were carried out via SigmaScan. Porosity analyzes of the samples were carried out by using the X-Ray radiography method, which is one of the most well-known non-destructive testing methods, for the RPT samples before cutting for surface analysis, for the lama tensile bar before the sample preparation for the impact test, and for the cylindrical tensile bar samples before the tensile test. Within the scope of mechanical characterization studies; The hardness measurements of the samples, impact tests, and tensile tests for the cylindrical tensile bar were performed and the effect of the increased amount of Sr on the mechanical properties of the AlSi12(Fe) alloy was investigated in detail. In order to observe the change in Si morphology depending on the increasing amount of Sr, microstructure analyzes of the samples were carried out. SEM imaging was performed for the intermetallic formed in the microstructure due to the increasing amount of Sr, and point, linear, and areal EDS analyses were performed on the relevant phases. As a result, it was observed that both the microstructural and mechanical properties of the alloy were positively affected due to the increased amount of Sr in the AlSi12(Fe) alloy produced by the HPDC. A significant improvement in yield strength, tensile strength and % elongation value of AlSi12(Fe) alloy was determined with increasing Sr content. According to the results of the notch impact test, the energy absorption ability of the alloy was improved with the increase in the amount of Sr. It was concluded that the ductility of the AlSi12(Fe) alloy was significantly improved with the use of 160 ppm Sr.