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      Permanent link:
      https://www.ias.ac.in/article/fulltext/boms/023/05/0405-0411

    • Keywords

       

      Two-step ageing; delayed ageing; clusters; coherency strains

    • Abstract

       

      In commercial practice, two-step ageing is commonly used in Al-Zn-Mg alloys to produce a fine dispersion of η′ precipitates to accentuate the mechanical properties and resistance to stress corrosion cracking. While this is true in Al-Zn-Mg alloys, two-step ageing leads to inferior properties in Al-Mg-Si alloys. This controversial behaviour in different alloys can be explained by Pashley’s Kinetic model. Pashley’s model addresses the stability of clusters after two-step ageing. In the development of the model, the surface energy term between cluster and matrix is taken into account while the coherency strains between the cluster and matrix are not considered. In the present work, a model is developed which takes into account the coherency strains between cluster and matrix and defines a new stability criterion, inclusive of strain energy term. Experiments were done on AA 7010 aluminium alloy by carrying out a two-step ageing treatment and the results fit the new stability criterion. Thus it is found that the new model for two-step ageing is verified in the case of Al-Zn-Mg alloy.

    • Author Affiliations

       

      K T Kashyap1 2 C Ramachandra1 B Chatterji1 S Lele1

      1. central materials and processes laboratory, foundry & forge division, hindustan aeronautics limited, bangalore - 560 017, india
      2. Department of Metallurgical Engineering, Banaras Hindu University, Varanasi - 221 005, India

    • Dates

       
      Published
      October 2000
      Manuscript received
      24 January 2000
      Manuscript revised
      4 May 2000

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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