Study on GP Zones Formation in the Sc Inoculated Ternary Al-Zn-Mg Alloys

Authors

  • P. K. Mandal Indian Institute of Technology Roorkee (IITR), Roorkee, Uttarakhand, India

Keywords:

GP zones, inoculation effect, XRD, TEM, activation energy, tensile properties

Abstract

Mostly, ternary Al-Zn-Mg (7075) alloys are used in automotive and aerospace engineering due to readily age-hardening response and high specific strength-to-density ratio. Scandium (Sc) has great inoculation effect in Al-Zn-Mg alloys. The cast Al-Zn-Mg alloys system undergoes a complex transition sequence in order to gain maximum strength. This sequence consists of solutionizing then immediate quenching in water (T4), natural ageing and artificial ageing (T6); usually, in several temperature steps to results in a structure of finely dispersed precipitates (Al3Sc). Quenching in water from the solution temperature 465oC/1 h induces severe internal stresses in the material; and introduction of dislocations in the supersaturated solid solution (SSSS) modifies the precipitation process. They act concurrently as vacancy sinks during room temperature ageing, which preferred nucleation sites and as short-circuit diffusion paths during later precipitation steps. The microstructure and the peak hardening effects are shown to depend on the competition between GP zones and nucleation of ή and/or nucleation of dislocations. According to the ageing, process starts with the diffusion of Zn to Mg atoms and GP zones develop by the formation of Mg-Zn clusters. The GP zones can act as prospective nucleation sites of more stable precipitates providing the basis of artificial ageing treatments applied to Al-Zn-Mg alloy systems. The kinetics of the activation energy have been studied on a number of three different Al-Zn-Mg alloys by Vicker’s hardness measurement between 120 and 180oC. A systematic investigation has been carried out to study the decomposition of the SSSS in the formation of GP zones and subsequent transition phases in the wide temperature range in Sc inoculated Al-Zn-Mg alloys. The influence of various process parameters on the microstructure and mechanical properties of the Al-Zn-Mg alloys are studied by OM, EBSD, FESEM, resistivity, XRD, DSC, TEM, and tensile properties. 

Author Biography

  • P. K. Mandal, Indian Institute of Technology Roorkee (IITR), Roorkee, Uttarakhand, India
    Department of Metallurgical and Materials Engineering

Downloads

Published

2019-04-10

Issue

Vol. 6 No. 2 (2016)

Section

Articles

License

Declaration and Copyright Transfer Form

(to be completed by authors)

I/ We, the undersigned author(s) of the submitted manuscript, hereby declare, that the above manuscript which is submitted for publication in the STM Journals(s), is not published already in part or whole (except in the form of abstract) in any journal or magazine for private or public circulation, and, is not under consideration of publication elsewhere.

  • I/We will not withdraw the manuscript after 1 week of submission as I have read the Author Guidelines and will adhere to the guidelines.
  • I/We Author(s ) have niether given nor will give this manuscript elsewhere for publishing after submitting in STM Journal(s).
  • I/ We have read the original version of the manuscript and am/ are responsible for the thought contents embodied in it. The work dealt in the manuscript is my/ our own, and my/ our individual contribution to this work is significant enough to qualify for authorship.
  •  I/We also agree to the authorship of the article in the following order:

Author’s name                                    

 

1. ________________

2. ________________

3. ________________

4. ________________

 

We  Author(s) tick this box and would request you to consider it as our signature as we agree to the terms of this Copyright Notice, which will apply to this submission if and when it is published by this journal.