Magnesium Alloy AZ91E and its Usage in Bicycle Frame Design

increase of the cyclic time results in the negative movement of corrosion potential and the
increase of current density. SEM observation indicates that corrosion occurs only in α phase, β
phase is inert in corrosive medium, and the corrosion of AZ91 magnesium appears in uniform
characteristic. XPS analysis suggests that the corrosion product is mainly composed of oxide and
hydroxide of magnesium and aluminum, and a small amount of sulfate is also contained in the
film.
Damping Behavior:- The amplitude-dependent damping of a commercial magnesium cast alloy
AZ91 has been determined at room temperature by measurement of the logarithmic decrement
of free decaying vibrations of bending beams clamped at one side. In order to generate cracks in
the specimens they were subjected to (1) isochronal heat treatments for 1 h at temperatures above
400 °C with succeeding quenching in cold water and (2) controlled fatigue bending loading in
the same equipment also used for the damping measurements. After both treatments, the
amplitude-dependent damping curves show a maximum for strains 10 −5 to 10 −3 , which can be
correlated with the presence of cracks and can be explained by a simple rheological model based
on crack damping. This maximum is enhanced when the number of loading cycles or the
quenching temperature is increased which can be explained by crack nucleation. Crack growth
with increasing number of loading cycles shifts the maximum to lower strains.