The purpose of this research was to obtain room temperature fatigue be
havior of AZ91E-T6 cast magnesium alloy and to determine if commonly u
sed models that depict fatigue behavior are applicable to this cast al
loy. Axial strain-controlled fatigue behavior using cylindrical specim
ens were employed to determine low cycle fatigue behavior with strain
ratios R = epsilon(min)/epsilon(min) = 0, -1, and -2. The conventional
log-log total strain low cycle fatigue model properly represented the
R = -1 axial fatigue data. Significant mean stress relaxation occurre
d for all R = 0 and -2 axial fatigue tests. However, for the smaller s
train amplitude tests with R = 0, sufficient mean stresses were retain
ed such that fatigue life was reduced. The mean strains/stresses had l
ittle influence on the cyclic stress-strain curve which exhibited cycl
ic strain hardening. Mean stress effects were analyzed using the Morro
w, SWT and Lorenzo-Laird models and similar, but oftentimes nonconserv
ative, calculations resulted. Region I and II fatigue crack growth beh
avior was determined using C(T) specimens with load ratios R = P(min)/
P(max) = 0.05 and 0.5. Values of DELTAK(th) and (DELTAK(th)eff were le
ss than 1.5 MPa square-root m and the Paris equation slopes were betwe
en 3.3 and 3.9. Quasi-cleavage was predominant for both fatigue crack
growth and final fracture regions. The commonly used low cycle fatigue
and fatigue crack growth models appear to reasonably represent most o
f the results with this AZ91E-T6 cast magnesium alloy.