INFLUENCE OF SHRINKAGE POROSITY ON THE FATIGUE BEHAVIOR OF CAST ALSI7MG

Cast defects are always present in aluminum castings due to the production process. Because of the negative influence of porosity on the fatigue properties, the porosity knowledge is the key-step in the fatigue life prediction of Al-Si castings. This contribution presents rotating bending fatigue tests that were planned and performed on specimens of modified AlSi7Mg cast alloy based on the largest defect size characterization by metallography. For the production of the fatigue test specimens, separately cast bars were produced with different treatments of the liquid metal before casting. The objective was to determine the role of modifiers on fatigue response using a limited number of test specimens. The largest defect size on individual specimens was predicted using a statistical pore size distribution obtained with metallography and used in fatigue test planning. Predicted and actual sizes of critical pores observed on the fatigue fracture surface of broken specimens were compared.