Microstructures and properties of low cycle fatigue of electrolytic A356 alloys

Microstructures and properties of low cycle fatigue of electrolytic A356 cast alloys with different Ti contents were investigated, and corresponding properties of melting A356 alloys were also investigated as a comparison. All tested alloys exhibited the evident cyclic hardening behavior, and the alloys with 0.14% Ti had the higher cyclic hardening rate than the alloys with 0.10% Ti. When tested at higher strain amplitudes, the cyclic stress amplitudes of electrolytic alloys remained basically in the quasi-stable state, while the cyclic stress amplitudes of melting alloys continuously proceeded. The fatigue life of the A356 alloy was controlled by Ti content instead of the Ti-addition method. In comparison to the alloys with 0.14% Ti, the alloy with 0.10% Ti exhibited the longer fatigue life due to its lower yield stress. The fatigue flats, coupled with some fatigue striations and fatigue slipbands, were observed to occur in the fracture surfaces of the electrolytic A356 alloy at lower strain amplitudes.

Research Highlights
► The electrolytic and melting A356 alloys exhibited the cyclic hardening behavior.
► Alloys with 0.10% Ti have the longer LCF life due to its lower yield stress.
► The fatigue flats, striations and slipbands were observed at low strain amplitudes.