Papers by Keyword: GP Zones

Paper TitlePage

Authors: F. Lourdjane, Z. Chaieb, A. Raho, M. Kadi-Hanifi
Abstract: The development of the transition metastable phases and the accompanying hardening of these transformations are studied for Al-20wt%Ag and Al-3wt%Cu-1wt%Mg supersaturated solid solutions. During the precipitation the GP and GPB zones form by a process of negative diffusion. The metastable phases are characterized by their hardness isotherms and their temperature range determined on the hardness isochronal.
Authors: V. Anil Kumar, Raghavendra R. Bhat, Romesh C. Sharma
Abstract: Aluminum alloys based on Al-Zn-Mg-Cu system classified under high strength light alloys, find a large scale application in aerospace sector. In the present study, heat treatment of an Aluminum alloy with Al-8Zn-2Mg-2Cu wt.% (AA7449) was carried out. Heat treatment parameters were optimized based on hardness and conductivity measurements. The mechanisms of strengthening in primary and secondary aged states are explained using hardness and conductivity measurements. Conductivity generally showed an increasing trend with increase in aging time, which could be attributed to decrease in the lattice distortion of the Aluminum matrix with increase in aging time. The dissolution of GP zones and formation of other metastable phases like η’ and stable phase like η were found to reduce the supersaturation in the matrix as the precipitation growth and coarsening processes are completed during overaging. Transmission electron microscopy (TEM) study was carried out to confirm the peak-aging regime. Selected Area Diffraction (SAD) patterns were recorded where GP zones and η’ precipitates were observed in the bright field images to establish their nature. The mechanical properties were correlated with the TEM observations and was suggested that a critical distribution of GP zones and η’ precipitates is essential to achieve peak strength in Al-Zn-Mg alloys.
Authors: P.K. Mandal
Abstract: The Al-Zn-Mg system is a familiar age-hardenable 7xxx series of aluminium alloy. Aluminium alloys are gaining wide popularity in aeronautical, automotive, and transportation industries. Scandium (Sc) has the ability to refine grain size of cast aluminium structure. It has been possible to achieve an ideal combination of strength, density, and thermal stability because of the unique age-hardening characteristics of Sc. Moreover, low solid solubility of Sc in aluminium is responsible for the improvement of the microstructure and mechanical properties when added in small amounts (≤0.6 wt.%). Further, inoculation is an effective means of grain refinement in liquid state of as-castaluminium alloys. So, density of GP zones formation and early stage of ageing effects assessment main priority in the present work. However, coherent precipitates like ScAl3are finely dispersed to provide thermal stability by increasing recrystallization temperature. Hence, the improvement in the high temperature stability of aluminium alloys (7xxx series) may be attributed to the grain boundary pinning (e.g. Zenerdrag mechanism) by the fine precipitates.In this paper, the relationship between the mechanical behavior and microstructure characteristics of Al-Zn-Mg-Sc based alloys are investigated to understand the thermal stability mechanism of grain refinement and dispersive precipitation.
Authors: Simon P. Ringer, S.P. Swenser, Barry C. Muddle, Ian J. Polmear, Takeaki Sakurai
Authors: K. Matsuda, H. Daicho, Gary J. Shiflet, Susumu Ikeno
Authors: Kosuke Kido, K. Matsuda, Tokimasa Kawabata, T. Sato, Susumu Ikeno
Showing 1 to 10 of 15 Paper Titles