The University of British Columbia

Research Interests

• Physical phenomena in non-ferrous casting: hot tearing
• Continuous Casting, EB Melting and Refining, Vaccuum Casting
• Finite element-based heat flow and stress codes
• Optimization of industrial casting processes
• Mathematical modeling

Thus far, my work has adopted an approach that combines both industrial and laboratory experiments with mathematical modeling. General finite element-based heat flow and stress codes have been developed in-house and applied, together with commercial codes, in the analysis, optimization and design of a number of industrial processes, focusing principally on casting technology. In the last 6 years I have received substantial support from industry for my effort as either the primary or co-investigator.

The expertise in heat transfer extends beyond the basics of heat conduction to include inverse conduction techniques, which have been applied to analyse complex industrial boundary conditions, solidification microstructure evolution in cast irons, freckle formation in nickel-based superalloys and hydrogen-based porosity formation in aluminum alloys . In the case of my thermal stress analysis activities, most of the effort has been directed toward the prediction of stress and strain evolution in casting processes with a view to reducing cracking and distortion and has involved both elastic and inelastic deformation. For example, a significant effort recently has been directed toward understanding and predicting the formation of hot tears in aluminum ingots that develop during the start-up phase of the direct-chill (DC) casting process and to understand mechanistically why some alloys are more sensitive to cracking than others (the DC casting process is the dominant industrial process used to produce aluminum sheet ingots).

Laboratory and industrial measurements continue to play a large role in my activities since, in many instances, the knowledge necessary to develop sophisticated process models does not exist within the literature. The data collected represents new knowledge and includes data related to heat transfer phenomena , data related to distortion phenomena data related to porosity formation, data related to the constitutive behaviour of alloys at high temperature, including in the semi-solid state , data related to defect formation in nickel-based superalloys and data related to the evolution in the solidification structure in various aluminum alloys . The collection of this data often represents a significant challenge and requires the use of sophisticated state-of-the art equipment and techniques. The industrial data in particular is often very difficult to acquire because of the need to work on production equipment, but is unique and often essential to our understanding of how these processes operate mechanistically.

As evidence of impact, many of the codes for which I have coordinated the development are actively in use by industry. Specifically, the code developed for Canadian Autoparts Toyota Inc. is being used in the design of die-tooling for the production of aluminum alloy wheels; the code developed for the TIMKEN Company is being utilized in the thermal-mechanical processing of steel tubing; and the code developed for Alcan Ltd. is being applied to optimize the casting recipe used during the start-up phase of the DC casting process. These are major international corporations with a significant impact on the global economy.

Primary collaborators: Dr. Daan Maijer (UBC), Dr. Mary Wells (Waterloo), Canadian Auto Part Toyota, Rio Tinto Alcan, The Timken Company.

Links: Centre for Metallurgical Process Engineering

Refereed Journal

1. S. Kim, S. L. Cockcroft, “Sintering Behaviour of Ultra-Fine Al2O3-(ZrO2+Xmol% Y2O3) Ceramics by High-Frequency Induction Heating”, Accepted for Publication April 2010, Materials Science and Engineering A, MSEA-D-10-00676.
2. H. Hao, D. M. Maijer, M. A. Wells, A. Phillion and S. L. Cockcroft, “Modeling the Stress-Strain Behavior and Hot Tearing During Direct Chill Casting of an AZ31 Magnesium Billet”, in press Metallurgical and Materials Transactions A, E-TP-09-635-AR, January 2010
3. S. Kim, S. L. Cockcroft, A. M. Omran and H. Hwang, “Mechanical, wear and heat exposure properties of compacted graphite cast iron at elevated temperatures”, accepted for publication in Journal of Alloys and Compounds, 2009, Vol. 487 (2009) 253–257
4. A. B. Phillion, S. L. Cockcroft, and P. D. Lee, “Predicting the constitutive behavior of semi-solids via a direct finite element simulation: application to AA5182”, Modelling Simul. Mater. Sci. Eng., 17 (2009) 055011 (15 pages).
5. O. Lashkari, L. Yao, S.L. Cockcroft, D.M. Maijer, “X-Ray Microtomographic Characterization of Porosity in Aluminum Alloy A356”, Metallurgical and Materials Transactions A: Volume 40, Issue 4 (2009), Page 991.
6. K. Hu, A.B. Phillion, D.M. Maijer, S.L. Cockcroft, "Constitutive behavior of as-cast magnesium alloy Mg-Al3-Zn1 in the semi-solid state" Scripta Mater. 60(6): 427-430. 2009.
7. A. B. Phillion, S. Verne`de, M. Rappaz, S. L. Cockcroft and P. D. Lee, “Prediction of solidification behaviour via microstructure models based on granular structures”, International Journal of Cast Metals Research, 22 (1-4): 2009.
8. S. Kim, S. L. Cockcroft and A.M. Omran, “Optimization of the Process Parameters Affecting the Microstructures and Properties of Compacted Graphite Iron” Journal of Alloys and Compounds, Vol. 476 12 May (2009), 728-732.
9. A. B. Phillion, S. Thompson, S. L. Cockcroft and M. A. Wells, “Tensile Properties of As-Cast Aluminum Alloys AA3104, AA6111 and CA31218 at Above Solidus Temperatures”, Mater. Sci. Eng. A., 497: 388-394:2008.
10. A.B. Phillion, P.D. Lee, E. Maire and S.L. Cockcroft, “Quantitative assessment of deformation-induced damage in a semi-solid aluminum alloy via x-ray tomography”. Metallurgical and Materials Transactions A, Vol. 39A, Oct., 2459-2469:2008.
11. A.B. Phillion, S.L. Cockcroft, and P.D. Lee, “A three-phase simulation of the effect of microstructural features on semi-solid tensile deformation”, Accepted to Acta Materialia” (ref. A-08-444) subject to minor revision, April, 2008.
12. A.B. Phillion, S.L. Cockcroft, R.C. Atwood, and P.D. Lee, “A New Methodology for Measurement of Semi-Solid Constitutive Behaviour and its Application to Examination of As-Cast Porosity and Hot Tearing in Aluminum Alloys”submitted to Materials Science and Engineering A, Accepted, January, 2008
13. D. Li, M.A. Wells, S.L. Cockcroft and E. Caron, Metallurgical and Materials Transactions B-Process Metallurgy and Materials Processing Science, Vol. 38, (6) 2007, pp. 901-910.
14. J. B. Mitchell, S. L. Cockcroft, D. Viano, C. Davidson, D. StJohn, “Determination of Strain during Hot Tearing by Image Correlation”, Metallurgical and Materials Transactions A, Vol. 38A, Oct. 2007, pp 2503 - 2512.
15. B. Zhang, D.M. Maijer and S.L. Cockcroft, “Development of A 3D Thermal Model of the Low-Pressure Die-Cast (LPDC) Process of A356 Aluminum Alloy Wheels, Materials Science and Engineering A, Vol. 464 , 2007, pp 295–305.
16. Phillion, A.B., Cockcroft, S.L., and Lee, P.D. "X-Ray Micro-tomographic Observations of Damage Caused by Hot Tearing in AA5182", Scripta Materialia, 55 (5), 2006, 489-92.
17. Mitchell, A., Kawakami, A., and Cockcroft, S.L., "Beta fleck and segregation in titanium alloy ingots, "High Temperature Materials and Processes, v 25, n 5-6, 2006, p 337-349.
18. J.D. Zhu, S.L Cockcroft and D.M. Maijer, Modeling of Microporosity Formation in A356 Aluminum Alloy Casting – The Role of Hydrogen Diffusion, Metallurgical and Materials Transactions A, 37A (2006), 1075-1085.
19. B. Zhang, S.L. Cockcroft, D.M. Maijer, J.D. Zhu, and A.B. Phillion, “Casting Defects in Low-Pressure Die-Cast Aluminum Wheels”, Journal of the Minerals, Metals and Materials Society, Vol. 57, No.11, Nov. 2005, pp. 36-43,, by invitation.
20. A. Mitchell, S.L. Cockcroft and T. Wang, “Some Observation on the Columnar-to-Equiaxed Transition in Nickel-base Superalloys”, High Temperature Materials and Processes, Vol. 24, No.2, 2005, pp. 131-138.

Refereed Conference

1. L. Yao, S.L. Cockcroft, D.M. Maijer and J.D. Zhu, “Effect of oxide films on microporosity formation in A356 aluminum alloy castings”, to appear in the Proceeding of the Conference of Metallurgists, Light Metals Symposium Vancouver 2010.
2. L. Yao, E. Khajeh, S.L. Cockcroft, D.M. Maijer, "Modeling of Porosity Size Distribution in A356 Tapered Cylinder Castings", Accepted Proc. 12th Intl. Conf. on Modeling of Casting, Welding and Solidification Proc., ed. by S.L. Cockcroft, and D. M. Maijer (2009).
3. A. B. Phillion, S. Vernède, M. Rappaz, S. L. Cockcroft, and P. D. Lee, “Prediction of Solidification Behaviour via Microstructure Models based on Granular Structures”, 17-20 June 2008, Austria.
4. J.B. Mitchell and S.L. Cockcroft, "Determination of Strain during Hot tearing in Aluminum Alloys by Digital Image Correlation", Proceedings of the Conference of Metallurgists, Hamilton, Ontario, 2007. Best Paper Award Light Metals Symposium, presented by J.B. Mitchell
5. A. B. Phillion, P. D. Lee, S. L. Cockcroft, “Damage Formation during the Deformation of a Solidifying Al-Mg Alloy”, Frontiers in Solidification Science, TMS Annual Meeting, Orlando FL, 2007.
6. A. Larouche, M. Lane, M. DiCiano, D.M. Maijer, S.L. Cockcroft, and R. Thiffault, “Understanding T-ingot Horizontal DC Casting Using Process Modelling”, Materials Science Forum, Vol. 519-521, Eds. W.J. Poole, M.A. Wells, and D.J. Lloyd, Trans Tech Publications, pp.1461-1466, July 2006.
7. A.B. Phillion, D.M. Maijer, S.L. Cockcroft, “Coupled Thermal-Stress Model of the Start-up Phase of the Aluminum Direct Chill Casting Process: Predictions Relating to Hot Tearing”, Proc. 11th Intl. Conf. on Modeling of Casting, Welding and Solidification Proc., ed. by C-A. Gandin, and M. Bellet, Opio, Fr, pp. 807-814, (2006).
8. B. Zhang, S.L. Cockcroft, D.M. Maijer and J.D. Zhu, “A Thermal Model of the Low-Pressure Die-Casting (LPDC) Process and its Application to Predict Porosity Formation in Aluminum Alloy Wheels”, Simulation of Aluminum Shape Casting Processing, EditedbyTMS (The Minerals, Metals & Materials Society), 2006.
9. J.D. Zhu, B. Zhang, S.L. Cockcroft and D. Maijer, "Simulation of Microporosity Formation in A356 Aluminum Alloy Casting - The Role of Hydrogen Transport", Light Metals Symposium - COM2005 - Calgary, Canada. Best Paper Award Light Metals Symposium, Conference of Metallurgists, Calgary 2005, presented by S.L. Cockcroft.
10. A. B. Phillion, S. L. Cockcroft, J. Sengupta, and D. M. Maijer, "Implementation of a Strain-Based Hot Tearing Criterion In Direct Chill Cast Aluminum Ingots", Light Metals 2005 Edited by Halvor Kvande TMS (The Minerals, Metals & Materials Society), 2005
11. H. Hao, D. M. Maijer, M. A. Wells, S. L. Cockcroft and R. B. Rogge, "Prediction and Measurement of Residual Stresses/Strains in a Direct Chill Casting Magnesium Alloy Billet", Magnesium Technology 2005 Edited by Neale R. Neelameggha, Howard I. Kaplan, and Bob R. Powell TMS (The Minerals, Metals & Materials Society), 2005

Conference

1. Daniel Larouche, Dung-Hanh Nguyen, Steve Cockcroft, André Larouche, "Mathematical Modeling of DC Cast Sheet Ingots using a Semi-solid Tensile Constitiutive Behaviour for Hot Tearing Prediction" Light Metals 2009 Edited by Pierre Le Brun and Hussain H. Alali, TMS (The Minerals, Metals & Materials Society), 2009
2. J.B. Mitchell and S.L. Cockcroft, "Determination of Strain during Hot tearing in Aluminum Alloys by Digital Image Correlation", Proceedings of the Conference of Metallurgists, Hamilton, Ontario, 2007.
3. S.L. Cockcroft, A.B. Phillion, J. Mitchell, D.M. Maijer and P.D. Lee, “The Role of As-Cast Porosity, Stress and Strain in Hot Tearing in DC Cast AA5182”, Proceedings of the 7th Pacific Rim International Conference on Modeling of Casting and Solidification Processes 2007, Eds. Jin Jun-ze, et al., pp. 17-24, August 2007. (Keynote).
4. M. Lane, M. DiCiano, D.M. Maijer, S.L. Cockcroft, and A. Larouche, “Mathematical Modeling of the Horizontal DC Casting Process for T-ingot Production”, The 7th Pacific Rim International Conference on Modeling of Casting and Solidification Processes, August 19-22, 2007, Dalian, China.
5. J. Zhu, X. Zhao, D.M.Maijer, S.L.Cockcroft, D. Tripp, “Steady-State Modeling of Electron Beam Melting and Casting of Ti-6Al-4V Alloy Ingots”, The 7th Pacific Rim International Conference on Modeling of Casting and Solidification Processes, August 19-22, 2007, Dalian, China.
6. X. Zhao, D.M. Maijer, S.L. Cockcroft, D.W. Tripp, S.Fox, J.Zhu, “A Three-Dimensional Steady State Thermal Fluid Model of the Ingot Casting Process Associated with Electron Beam Melting of Ti-6Al-4V”, Proceedings of The 11th World Conference on Titanium, June 3-7,2007, Kyoto, Japan.