ARTÍCULO
PRECIPITATION HARDENING ANALYSIS OF AN Al-8%Ag ALLOY
Sergio Eliseo Hernández MartÃnez1,2a*, Jorge GarcÃa Rocha1,2b,
José de Jesús Cruz Rivera1,2c, José Luis Hernández Rivera2
Advanced Materials Research Vol. 976 (2014) pp 154-158
Online available since 2014/Jun/30 at www.scientific.net
© (2014) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.976.154, 2014.
ABSTRACT:
Aluminum alloys are important in aerospace industry, due to their mechanical properties, low specific weight and good corrosion resistance. Such properties are achieved due to a heat treatment of solubilization, quenching and aging, in order to precipitate metastables phases, which act as dislocation obstacles, increasing the strength of the alloy. In the present study, the precipitation sequence of Al-8%Ag alloy was analyzed via Vickers hardness and Transmission Electron Microscopy. The size and morphology of the precipitated particles, involved in the stages of precipitation process was characterized. It was determined the microstructure at the peak hardness, which is mainly composed of spherical GP zones with about 6 nm average diameter, which are responsible for the alloy achieve a value of 72 HVN. It was observed that this hardness value does not compete with others well known alloys, like AA 6061 and AA 2024, which can be precipitation hardened. The main reason for the low values of HVN, is because of there is no enough difference between the matrix and the precipitated particles lattice parameters, and don’t cause a significant elastic strain by coherence in the matrix lattice, that could produce a substantial hardening. To ascertain this assumption, the aged material was severely plastic deformed, achieving 94 HVN, and the grain refinement and high dislocations density were the major hardening mechanisms, since the precipitates behavior was similar as the matrix, because particles were distorted instead of acting as impediment to material flow.