Effect of solidification cooling rate on the fatigue life of A356.2-T6 cast aluminium alloy

Citation
B. Zhang et al., Effect of solidification cooling rate on the fatigue life of A356.2-T6 cast aluminium alloy, FATIG FRACT, 23(5), 2000, pp. 417-423
Citations number
14
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science & Engineering
Journal title
FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES
ISSN journal
8756-758X → ACNP
Volume
23
Issue
5
Year of publication
2000
Pages
417 - 423
Database
ISI
SICI code
8756-758X(200005)23:5<417:EOSCRO>2.0.ZU;2-6
Abstract
The effect of the cooling rate during solidification on the fatigue life of a cast aluminium alloy (A356.2-T6) is examined. The fatigue lives were det ermined for specimens removed from ingots with a gradient in cooling rates along their heights. Low- and high-cycle fatigue tests were conducted under both axial loading and reciprocating-bending conditions at a stress (strai n) ratio (R) of -1.0, 0.1 and 0.2. Results show that the fatigue life decre ases by a factor of three in low-cycle fatigue (R = -1.0) and by a factor o f 100 in high-cycle fatigue (R = 0.1) as solidification cooling rate decrea ses from similar to 10 to similar to 0.3 K s(-1), as indicated by measureme nts of the secondary dendrite arm spacings in the ingots. Fatigue cracks in itiated from porosity in the material solidified at slower cooling rates. W hen pore size is below a critical size of similar to 80 mu m, as a result o f increasing the cooling rate, the fatigue cracks initiated from near-surfa ce eutectic-microconstituent. When present at or near the surface, large ox ide inclusions initiated fatigue cracks.