Effects of Si contents and pre-strain on aging behavior in Al–Mn–Mg alloys containing a small amount of Cu

The paper reports the research results on precipitation hardening potentials of Al-Mn-Mg alloys containing a small amount of Cu, during aging at 150 degrees C. The age-hardening response and phase transformation are significantly affected by the Si content of the order of 0.1%. The hardening response increases during aging with increasing Si content. The hardening potential decreases significantly by tensile deformation prior to heat treatment. The pre-strain causes an inhomogeneous nucleation of precipitation on dislocations and cell walls and restricts transgranular precipitation during aging. In 10% pre-strained alloys, short-term aging leads to dislocation recovery, resulting in an increase in the n-value. Further decrease in dislocation density and increase in the n-value occur due to a small degree of precipitation hardening in a 0.15%-Siadded alloy, whereas dislocation recovery is suppressed by competitive precipitation in a 0.36%-Si-added alloy during prolonged aging.