The low cycle fatigue behavior of ZL101-T6 aluminum alloy has been investigated

focusing on the crack initiation and propagation in the alloy

by scanning electronic microscope （SEM） and metallographic microscope. The results show that the crack of eutectic Si phase is mainly responsible for the low cycle fatigue crack initiation. The amount of crack Si particles is increased with increasing in fatigue cycles

and the crack rate of Si particle

which can be accelerated with the increase of strain amplitude

promotes the propagation rate of fatigue crack. The propagation of fatigue crack is mainly dependent on the connection of adjacent cracking eutectic Si particles during initial cycling stages. With the growth of micro-crack

transgranular coalescence can be taken place in Al matrix to form a long fatigue crack

resulting in the final rupture of the alloy. So the final rupture in the ZL101 aluminum alloy is characterized by the transgranular fracture.