Thermo-mechanical Fatigue Behaviour of AlSi7Mg Alloy Processed by Selective Laser Melting

Heat treatable hypo-eutectic AlSi7Mg (A357) alloy is widely used for lightweight structural parts and for high temperature applications such as in cast cylinder heads.
AlSi7Mg is also a suitable alloy to be processed by selective laser melting (SLM), owing to its narrow solidification range, resistance to hot cracking and good fluidity. Employing SLM-processed parts made by AlSi7Mg in high temperature applications with cyclic thermal loads requires good resistance to thermo-mechanical fatigue due to the critical strains and stresses induced by the fluctuating temperature. In this study, the thermo-mechanical fatigue behaviour of A357 alloy samples produced by SLM has been investigated using a Gleeble®3800 simulator. A correlation has been found between the applied mechanical stress and thermo-mechanical fatigue life. Analyses on the mechanisms of failure allowed to draw conclusions about the relation between the thermo-mechanical fatigue strength and peculiar microstructure formed by SLM-processing.