Fatigue crack propagation in Al-Si alloy castings.

Abstract

Permanent mold castings of high purity binary Al-Si alloys (Si: 3, 7, 12 and 20%) were tested. The fatigue crack propagation in as-cast alloys in the Paris regime is seriously influenced by Si concentration less than eutectic composition. Al-20%Si alloy is less stable in fatigue crack propagation than the other alloys. Solution treated high Si alloys show slower rates of fatigue crack propagation than as-cast alloys. The fact depends on strengthening of the matrix, forming of eutectic Si particles into spheres and on increase in crack closure. The resistance to fatigue crack initiation is improved by high content of Si in as-cast alloys and by solution treating.

Effect of Pro-eutectoid Cementite on Fatigue Crack Growth Behavior of Pearlitic Steels

“…Static fracture phenomena of the hard second phase during fatigue crack growth have been reported in metal matrix composites containing a compound phase such as SiC particle-reinforced Al alloy composites, 24,25) WC-Co based cemented carbides [26][27][28] and Al-Si based casting alloys with hard Si particles as the second phase. [29][30][31][32][33] Kobayashi et al 24) investigated the SiC particle behavior during fatigue crack growth in Al alloy composites, and pointed out that fatigue crack growth was promoted by delamination between the SiC particles and the matrix and/or cleavage cracking of the SiC particles themselves, and the crack growth rate was accelerated by an increase in the SiC volume fraction. In addition, Sunouchi et al 28) examined the fatigue crack growth mechanism of WC-Co sintered materials using an acoustic emission technique, and concluded that the crack growth rate was accelerated by brittle fracture of WC particles and the particle fracture frequency increased with an increase of K max .…”

Fatigue life prediction of pre-corroded AZ31 magnesium alloy based on surface topology

“…The critical point of stress intensity factor (DK) in fracture mode defined as fracture toughness (K IC ) of the material which is ranged in 17.6-20.7 MPa ffiffiffiffi m p for AZ31B magnesium alloy. 44,45 The relationship between the virtual crack size and the corrosion time was obtained by curve-fitting, as reported in equation (11).…”

“…The virtual crack size is only affected by the corrosion time, and no significant influences could be observed on virtual crack size upon increasing the maximum stress. Thus, in Table 6, the mean values of different corrosion times have also been reported and used to propose equation (11).…”

“…In that study, fatigue crack was observed to initiate from inclusions and corrosion pits. The influence of the corrosive environment on the fatigue behavior of the AZ31 magnesium alloy was explored by Kobayashi et al 11 Shorter corrosion fatigue lives were observed compared to laboratory environment fatigue tests. 11 Environmental effects on the HCF behavior of the magnesium alloys AZ31 and AZ80 were studied by Hilpert and Wanger.…”

“…The influence of the corrosive environment on the fatigue behavior of the AZ31 magnesium alloy was explored by Kobayashi et al 11 Shorter corrosion fatigue lives were observed compared to laboratory environment fatigue tests. 11 Environmental effects on the HCF behavior of the magnesium alloys AZ31 and AZ80 were studied by Hilpert and Wanger. 12 No fatigue life reduction was seen in a corrosive environment compared to air at high-stress amplitudes.…”