Fig. 1 Schematic and specimen for fatigue test

Fig. 2 S-N curves of A356.2 alloys under different conditions: a as-cast, b T6 treated

Fig. 3 Variation in cyclic strain amplitudes of T6 alloys treated by Al-5Ti-1B/Al-10Sr a, Al-6Sr-7La b

Fig. 4 Morphologies of eutectic Si extracted by deep etching a unmodified, b traditional treated alloy, c alloy treated by Al-6Sr-7La

Fig. 5 Dislocation accumulation around eutectic Si a without cyclic loading, b after 6324 cycles, c after 110,441 cycles

Fig. 6 Slip bands after different levels of cyclic fatigue deformation a after 6324 cycles; b after 34,851 cycles, c after 110,441 cycles

Fig. 7 Precipitates in traditional treated alloy a and Al-6Sr-7La treated alloy b, HRTEM of spherical cross section c and short rod-like cross section d

Fig. 8 Typical cooling curves of the alloys treated by different refiners and modifiers

Fig. 9 Eutectic Si in traditional treated a, Al-6Sr-7La treated b alloys

Fig. 10 a, b HRTEM results of intersecting twins in eutectic Si, c EDX analysis

Fig. 11 Al-6Sr-7La treated alloy: a overall morphology of eutectic Si, b c dark-field images of corresponding area in a at higher magnification

Fig. 12 Bright-field TEM images of Al-6Sr-7La modified alloy: a overall morphology of eutectic Si, b corresponding area in a at higher magnification, c nanoparticles, d stacking faults

Fig. 13 a Fatigue fracture surface under stress amplitudes of 180 MPa, b c crack initiation

Fig. 14 Fatigue crack initiation: a surface inclusions, b internal inclusions, c surface pores, d internal pores

Fig. 15 Fatigue striations in the alloys after different cycles: a 6324, b 24,931, c 34,851, d 60,123, e 87,263, f 110,441

Fig. 16 Fractured a eutectic Si, b iron-rich phase in FCG zone

Fig. 17 a TEM image of iron-rich phase, b SAED results