Solute clustering behavior between 293K and 373K in a 6082 Aluminum alloy

V.NOSEDA GRAU; A. CUNIBERTI; A. TOLLEY; M. V. CASTRO RIGLOS; M. STIPCICH

JOURNAL OF ALLOYS AND COMPOUNDS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2016 vol. 684 p. 481 - 487

0925-8388

We present a systematic study of the effect of pre-ageing between 293 K and 373 K in a 6082 Aluminum alloy using mainly differential scanning calorimetry in combination with Vickers hardness and transmission electron microscopy. The pre-ageing effects are characterized through the modifi-cations of the b00 precipitation DSC signal. Pre-ageing at 293 K leads to a progressive increase of the peak temperature, until it reaches a plateau at long aging times (250min), while pre-ageing at 373 K leads to a continuous decrease of the peak temperature. The results indicate the formation of two different types of clusters, named 1 and 2, below and above a pre-ageing transition temperature,determined to be around 343 K. After pre-ageing below 343 K, the dissolution of clusters 1 superimposed with the b00 precipitation occurs, and the enthalpy change remains almost independent of preageing time. Instead, pre-ageing above 343 K leads to the formation of type 2 clusters that transform on heating into beta" phase precipitates, with a decreasing enthalpy change as pre-ageing time increases.This result indicates that clusters 2 evolve during pre-ageing, reaching a structure/composition with formation enthalpy similar to that of b00 phase. Vickers hardness reveals the different evolution of both types of clusters with aging time. Transmission electron microscopy observations on samples subsequently aged at 453 K, show that type 2 clusters favour the nucleation of b00 precipitates, while type 1 clusters hamper such nucleation process.