Influence of natural aging on the precipitation hardening of an AlMgSi alloy

A. CUNIBERTI; A. TOLLEY; M. V. CASTRO RIGLOS; R. GIOVACHINI

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

ELSEVIER SCIENCE SA

Año: 2010 vol. 527 p. 5307 - 5311

0921-5093

The influence of natural aging on precipitation hardening of an Al–Mg–Si alloy was investigated bymechanical testing and quantitative transmission electron microscopy. It was found that natural agingincreases yield stress and reduces ductility, which is attributed to the formation of Mg/Si clusters. Theevolution of tensile properties saturates after around 7 days natural aging. Artificial aging for 30 min at180 ◦C after solution treatment resulted in an important increase in yield strength and loss of ductility,due to the rapid precipitation of the intermediate phase. Previous natural aging progressively reducesthe strengthening effect of 30 min/180 ◦C artificial aging, completely suppressing it after 7 days pre-aging.Microhardness evolution during 180 ◦C artificial aging was followed in samples that were aged immediatelyafter quenching, and with 7 days natural aging before artificial aging. In addition, microstructuralcharacterization using TEM was carried out at specific artificial aging times. Previous natural aging wasfound to reduce the initial hardening rate, producing a delay in the formation of precipitates. Thepeak-aging condition was reached almost at the same aging time. However, longer precipitates witha lower volume fraction were observed when artificial aging was preceded by natural aging.