Metal Processing Institute
Advanced Casting Research Center

Research Programs

Optimization of Heat Treatment Using Fluidized Bed (FB) Reactors

Research Team:

Sujoy Krishna Chaudhury
Diran Apelian


The goal of this project was to develop the fundamental knowledge base for heat- treating of aluminum components using fluidized bed (FB) reactors. Specifically, we studied the kinetics of phase transformation and microstructural evolution during post solidification heat treatment of cast aluminum components through FB processing. The microstructure and properties of cast aluminum components that are heat-treated in FB were compared to their counterparts that were conventionally heat-treated. Within the scope of this project we assessed the economical benefits and environmental impact of FB reactors.

Project Overview

Heat treatment characteristics of T4 (solutionizing, quenching, and natural aging) and T6 (solutionizing, quenching, and artificial aging) tempered cast alloys were studied. Castings were heat treated using fluidized bed (FB). For comparative purposes, castings were also heat treated using conventional furnace (CF). In case of SSM A357 alloy, the casting was heat treated to T5 temper (artificial aging) using both FB, and CF. Detailed microstructural characterizations were carried out using both optical and scanning electron microscopy. Microstructural evolution during various stages of heat treatments such as solutionizing, quenching, and aging were analyzed and studied with the use of thermal analyses. Finally, tensile properties were correlated with their resultant microstructures.

The project was divided into three phases. These are:

This project commenced in April 2002 and ended in May, 2005; the project was funded by the ACRC consortium members. Several important research findings were found, which are pertinent to both the scientific and industrial communities. The primary objective of this project was to develop a fundamental understanding of fluidized bed heat treating of Al castings and optimize their processing parameters. Some salient features of fluidized beds are: 1) high heating rate, 2) uniform heating of castings, 3) excellent temperature uniformity within the bed, and 4) environmentally friendly. These advantages were partly realized during the past three years through extensive experiments and analysis on heat treating of various cast alloys. Various castings selected for this study, can be grouped into two major categories. These are

  1. Al-Si-Mg (A356-with low Mg content (~0.35%), and D357-with high Mg content (~0.6%), and
  2. Al-Si-Cu-Mg (354 alloy-with low Cu content (~1.81%), and 319 type alloy-with high copper content (~3%).

These alloys were all grain refined and also modified with Sr. In case of D357 alloy, the heat treatment characteristics of both unmodified and Sr modified alloys were studied. These alloys are commonly used in industry for various automotive applications and were chosen for this study because of the strong interest and support from of our consortium members. In addition to conventional casting (i.e. liquid state), some selected studies were also made on heat treatment characteristics of semi-solid cast A357 alloy.

Outcome / Impact

Some salient conclusions for each alloy studied in this project are given below:

A356 alloy - T4 and T6 temper

D357 alloy - T4 and T6 temper

354 and 319 alloys - T4 and T6 temper

Quench sensitivity (D357, 354, and 319 alloys) - T4 and T6 temper

A357 SSM alloy - T5 temper


  1. D. Apelian, M.M. Makhlouf, C. Bergman, and J. Rosendahl, "Fluidized beds: An energy efficient alternative to conventional heat treatment operations", in proceedings of the MPMD fourth global innovation symposium: Efficient Manufacturing Processes, TMS, Edited by I. Anderson, T. Marechaux, and C. Cockrill, 2003.
  2. M. M. Makhlouf, D. Apelian, S.K. Chaudhury and C. Bergman, " Heat treatment of aluminium cast components in fluidized bed", in proceedings of the 1st International Light Metals Technology Conference, Brisbane, Australia, 18-20 September, 2003, Edited by A. Dahle, P. 371-376.
  3. S.K. Chaudhury, S. Shankar, D. Apelian, and J. Vanwert, "Short Cycle Heat Treating with Fluidized Beds: Structure Evolution", in proceeding of International Conference on Structural Aluminum Castings, Orlando, Florida, USA, November 2-4, 2003.
  4. S.K. Chaudhury, L. Wang, and D. Apelian, "Fluidized Bed Reactor Heat Treatment of A356 Alloy: Microstructure Analysis and Mechanical Properties", AFS Transactions, 112, 04-055, 2004.
  5. S.K. Chaudhury, Q. Pan, J. Heimsch, and D. Apelian, "Response of semi-solid processed Al based cast alloy during fluidized bed heat treatment", in proceedings of 8th International Conference on Semi Solid Processing of Metals and Alloys, Limassol, Cyprus, 21-23 September, 2004, published by NADCA, Wheeling, Illinois.
  6. D. Apelian and S.K. Chaudhury, "Fluidized bed heat treatment of aluminum cast components", Journal De Physique IV, December, 120, p. 555-562, 2004.
  7. S.K. Chaudhury, D. Apelian, "Fluidized Bed Heat Treatment of Cast Al Alloys", in Shape Casting: The John Campbell Symposium, published by TMS - ISBN # 0-87339-583-2, pp 283-293 (2005).
  8. S.K. Chaudhury and D. Apelian, "Effects of solution heat treatment on microstructure and mechanical properties of Al-Si-Cu-Mg (354) alloy using a fluidized bed reactor", AFS Transactions, 113, 05-071, 2005.
  9. D. Apelian and S.K. Chaudhury, "Heat treatment of Aluminum cast components-Recent developments and future challenges", World Foundry Organization Congress, St. Louis, MO, USA, April, 2005.
  10. S.K. Chaudhury and D. Apelian, "Effect of rapid heating on solutionizing characteristics of Al-Si-Mg alloy using a Fluidized bed", Metallurgical and Materials Transaction A, 37A, March, p. 763-778, 2006.
  11. S.K. Chaudhury and D. Apeilan, "Fluidized bed heat treatment of cast Al-Si-Mg-Cu alloys", Metallurgical and Materials Transactions A, 37A, p. 2295-2313, 2006.
  12. S.K. Chaudhury and D. Apelian, "Effect of rapid heating on aging characteristics of T6 tempered Al-Si-Mg alloy using a Fluidized bed", Journal of Materials Science, 41, p. 4684-4690, 2006.
  13. S.K. Chaudhury and D. Apelian, "Effects of fluidized bed quenching on heat treating characteristics of cast Al-Si-Mg and Al-Si-Mg-Cu alloys", International Journal of Cast Metals Research (in press), 2006.

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