Microstructural factors of low cycle fatigue damage in two phase Al–Si alloys

Double-stage hardening behavior and fracture characteristics of a heavily alloyed Al–Si piston alloy during low-cycle fatigue loading

“…In the present Al-Si alloy, there are a great number of intermetallic particles coupled with plate-like Si particles. The test for the typical hypoeutectic, eutectic and hypereutectic binary Al-Si alloys shows that these alloys exhibit single cyclic softening [24]. Therefore, the double-stage hardening in the present Al-Si piston alloy cannot be simply ascribed to the existence of Si particles in its microstructure.…”

“…The curve consists of four distinct stages: (1) initial rapid hardening; followed by (2) basically invariant stress amplitude; (3) the second progressive hardening; and (4) the second invariant stress amplitude to failure. The LCF behavior of the present Al-Si piston alloy with respect to cyclic hardening is radically different from the simple hardening or/and softening in the other aluminum alloys [4,[24][25][26][27][28][29][30][31][32][33][34][35][36]. The previous cyclic stress responses could be generally described as a single softening [24,27,29,32], or single hardening [4,25], or simple composite of softening/hardening process [28].…”

“…The previous cyclic stress responses could be generally described as a single softening [24,27,29,32], or single hardening [4,25], or simple composite of softening/hardening process [28]. As revealed in binary Al-Si alloys [24], the primary/eutectic Si particles do not contribute to the unusual stress response. Although there is a great deal of intermetallic compounds in this piston alloy, it cannot be simply speculated that these intermetallics result in the unusual cyclic hardening behavior.…”

“…Large primary Si particles may act as preferential cracking initiation sites [17,23]. For the simplified Al-Si binary eutectic alloys without casting defects, cracks initiate at the Al-Si interface [24]. In the absence of pores, the fractured Si particles have been found to cause microcrack formation and the existing Si particles to act as barriers for crack propagation [20].…”

Usable Properties of AlSi7Mg Alloy after Sodium or Strontium Modification

“…When evaluating the parameter λ E , 350 crossings of the measuring line with individual particles were analysed. For calculations aimed at determining maximum length of silicon precipitates l maxSi , significance of which in Al-Si alloys cracking tests is emphasised in [16,17], distances between 100 pairs of particles were taken into account.…”