Apelian Participates in GM Powertrain 2003 Advanced Materials Conference (November 2003)

Nov. 13, 2003, Pontiac

With increasing competition in automotive market, it is important for the World's No. 1 automaker to continue improvements in materials and processes and in particular to increase technological content so as to bring low cost and high performance products to the market.

Materials Engineering Department at GM Powertrain has planned to organize an annual Advanced Materials Conference that will provide opportunities for Powertrain product and manufacturing engineers to learn the latest development of advanced materials technologies, especially in the areas that GM Powertrain has leveraged and sponsored. This year's conference is scheduled for one-day meeting with emphasis on aluminum casting related activities including physical metallurgy, fatigue properties, heat treatment, and machining of aluminum castings. Three sessions are scheduled accordingly: Session I: Aluminum Casting and Fatigue Properties; Session II: Heat Treatment; and Session III: Machining of Aluminum Alloys. Five speakers from three universities are invited to give presentations. They are: Prof. Diran Apelian, Director of Metal Processing Institute at WPI; Prof. Fawzy Samuel, Industrial Research Chair at University of Quebec at Chicoutimi; Prof. M. Hamed, Director of Thermal Processing Laboratory at McMaster University, Ms. M. Dumitrescu, Principal Research Engineer at McMaster University, and Dr. Eugene Ng from McMaster University.

2003 ADVANCED MATERIALS CONFERENCE

GM Powertrain Engine Engineering
823 Joslyn Ave. Pontiac, MI 48340

November 13, 2003, Kettering Center (1AM28C)

Conference Program

8:20AM Introduction

SESSION I. ALUMINUM CASTING AND FATIGUE PROPERTIES

Chair: Herb Doty

8:30AM Fatigue Studies in Al-Si-X Cast Alloys - An Example of Industry-University Alliances in Action (The MPI model)
Prof. Diran Apelian, MPI, Worcester Polytechnic Institute

9:15AM Influence of Inclusions on the Nucleation of the -Al Phase in Al-Si-Fe Alloys
Prof. F.H. Samuel, University of Quebec at Chicoutimi

10:00AM Break


SESSION II. HEAT TREATMENT
Chair: Dave Paluch

10:30AM Short Cycle Heat Treating with Fluidized Bed: Microstructure Evolution
Prof. Diran Apelian, MPI, Worcester Polytechnic Institute

11:15AM Determination of Heat Transfer Rates during Cooling of Aluminum Castings Using Impinging Air Jets
Prof. M. Hamed, McMaster University, Canada

12:00PM Lunch Break


SESSION III. MACHINING OF ALUMINUM ALLOYS

Chair: Dave Shea

1:00PM Auto 21 Project: Machinability of Aluminum Alloys A356 - Experimental Investigation
Ms. Miky Dumitrescu, McMaster University, Canada

1:45PM Finite Element Modeling for Machinability Aspects of Aluminum Alloys
Dr. Eugene Ng, McMaster University, Canada

2:30PM Q&A
3:00PM Adjourn


ORGANIZERS:

8:30 am Fatigue Studies in Al-Si-X Cast Alloys - an example of Industry-University Alliances in Action (The MPI model)

D. Apelian and D. Lados
Metal Processsing Institute (MPI)
WPI, Worcester, MA 01609

Abstract

Industry-University collaboration is highly encouraged, and often incentives have been created by Federal agencies and other organizations to "mandate" such collaborations. However, the execution of industry-university collaborations requires specific factors and resources, as well as social factors. These issues will be addressed through an overview of the Metal Processing Institute (www.wpi.edu/Academics/Research/MPI/) established at WPI in the early 90's, and specifically, the Advanced Casting Research Center (ACRC). Fatigue studies in Al-Si-X alloys will also be reviewed, as an example of a an industry-university collaborative effort to expand and establish the knowledge base, as well as to disseminate this much needed knowledge base.

Speaker Biography

Dr. Diran Apelian is Howmet Professor of Engineering and Director of the Metal Processing Institute at Worcester Polytechnic Institute (WPI). He received his B.S. degree in metallurgical engineering from Drexel University in 1968 and his doctorate in materials science and engineering from MIT in 1972. He worked at Bethlehem Steel's Homer Research Laboratories before joining Drexel University's faculty in 1976. At Drexel he held various positions, including professor, head of the Department of Materials Engineering, associate dean of the College of Engineering and vice-provost. He joined WPI in July 1990 as the Institute's Provost. In 1996 he returned to the faculty and heads the activities of the Metal Processing Institute. He is credited with pioneering work in various areas of solidification processing, including molten metal processing and filtration of metals, aluminum foundry engineering, plasma deposition, and most recently, spray casting/forming. Apelian is the recipient of many distinguished honors and awards, has over 350 publications to his credit, and serves on several technical and corporate boards. He is Chief-Editor of the Journal of Light Metals, and serves on several editorial boards.

9:15 am Influence of Inclusions on the Nucleation of the -Al Phase in Al-Si-Fe Alloys

W. Khalifa1, F. H. Samuel1, J. E. Gruzleski2
1Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada
2McGill University, Montreal, Québec, Canada

Abstract

Systematic inoculation experiments were carried out to study the influence of various inclusions on the nucleation of the -Al phase in Al-Si-Fe alloys at different cooling rates. The results showed that in the dilute alloys, containing less than 1.5 pct Si + Fe, almost all the inclusion types have high percentages of occurrence within the -Al phase, indicating that nucleation is promoted on the surface of such inclusions. In a hypoeutectic Al-Si alloy containing 6.3 pct Si, the inclusion particles of MgO, TiB2, TiC, -Al2O3, and SiC become mostly inactive nucleants and are pushed to the interdendritic regions because of the dominating poisoning effect of Si. The current results were used successfully to explain the efficiency differences between the commercial grain refiners in the hypoeutectic Al-Si alloys. Si is observed to preferentially segregate to the liquid-Al/inclusion interfaces so as to lower the free energy of such interfaces. A theoretical analysis of the poisoning effect of Si showed that Si segregation to the liquid/nucleant interface alters the interfacial energy balance so that the catalytic efficiency of the nucleant particles is dramatically reduced. Careful analysis showed that the poisoning effect of Si in the hypoeutectic alloy is overcome when the nucleant particles have active surface characteristics as represented by the high catalytic potencies of -Al2O3, CaO and Al4C3 particles in nucleating the -Al phase of the hypoeutectic Al-Si alloy. Although some inclusions have comparable or higher occurrence levels than TiB2 in the -Al phase they cannot be used as efficient nucleants because of either their poor wettability with liquid aluminum or their chemical reactivity that can change the alloy chemistry.

Speaker Biography

Prof. Fawzy H. Samuel received his Bachelor's and Master's and Ph.D. in Metallurgical Engineering (1978-79). His research and professional experience includes Scientist at National Research Centre, Cairo, Egypt.; Scientist at Central Metallurgical Research and Development Institute, Helwan, Cairo, Egypt; Research Professor at the Ecole des Mines de Nancy, France (1983-1985); Research Associate in McGill University (1987-1989); Professor and Chair Incumbent of Alcan-NSERC-UQAC Industrial Research Chair (IRC) on Solidification and Casting of Aluminum (1990-1994); and Professor and Chair Incumbent of GM-NSERC-UQAC IRC on Advanced Technology of Light Metals for Automotive Applications (2000-to date).

He has supervised about 29 Master's and Ph.D. theses (UQAC) and 2 theses from Nancy, France.

He has published about 160 research articles in various international journals and 20 industrial reports. He holds 1 patent on strip rolling of interstitial-free steels (McGill University, with Prof. J.J. Jonas).

10:30AM Short Cycle Heat Treating with Fluidized Beds: Microstructure Evolution

D. Apelian and S. Chaudhury
Metal Processsing Institute (MPI)
WPI, Worcester, MA 01609

Abstract

Typically, for aluminum cast alloys, the total time taken to heat treat (solutionize and age) components in a conventional air convection furnace is anywhere up to 20 hours. However, heat treating the cast part in a fluidized bed furnace reduces the total time by an order of magnitude. A comparative study on heat treating in a conventional air convection furnace and a fluidized bed reactor will be presented. This study was performed on the Al-Si-Mg alloy system due to its commercial importance. The microstructural changes of the eutectic Si and Fe rich intermetallic phases during solutionzation, as well as the precipitation kinetics of Mg2Si phase during ageing are presented. Results indicate that the rate of heating in the furnace (kinetics) is critical in influencing the resultant structure during solutionizing and ageing of the alloy.

11:15AM Determination of Heat Transfer Rates during Cooling of Aluminum Castings Using Impinging Air Jets

Dr. M. S. Hamed
Thermal Processing Laboratory
Department of Mechanical Engineering, McMaster University
Hamilton, Ontario, Canada

Abstract

Rapid Cooling (Quenching) is regarded as one of the most critical steps in thermal processing of metal parts. High cooling rates determine the distribution of phase transformations, stresses, deformation and distortion after quenching, which in turns affect the quality of the produced part.

Quenching systems utilizing impinging air jets have been widely used in many thermal-processing operations, especially for the heat treatment of Aluminum alloys. The design of these systems requires estimation of cooling rates and cooling times of the processed parts. The accuracy of these estimates depends upon accurate determination of the surface heat transfer coefficients during the cooling process.

An algorithm, utilizing the concept of heat transfer dimensionality, was developed to calculate the heat transfer coefficients. The development and verification of the algorithm has been carried out using a combination of analytical and numerical approaches utilizing experimental data obtained for a wide range of jet parameters. Results show that the developed algorithm can accurately predict heat transfer rates for parts with complicated geometries.

Speaker Biography

Dr. Hamed has a PhD in Materials and Mechanical Engineering. He has worked in the field of thermal processing as director of R & D for five years. Currently, Dr. Hamed is a faculty member at the Department of Mechanical Engineering and Director of the Thermal Processing Laboratory (TPL) at McMaster University, Hamilton, Ontario, Canada.

1:00PM Auto 21 Project: Machinability of Aluminum Alloys A356 - Experimental Investigation

Ms. Miky Dumitrescu,
McMaster University, Canada

Abstract

The project objective is to develop/improve the high speed and ultra high speed machining methods for automotive parts that will constitute essential components in lightweight vehicles. High speed machining (HSM) is a subject that has presented special interest to both academic and industrial researchers for more than two decades. The advantages of this process are evident in terms of productivity, machining accuracy and surface finish. However, many issues related to tooling and machine design must still be addressed especially in speed ranges above 2000 m/min. A key obstacle to developing HSM technology for affordable mass production is the cost and robustness of tool materials and manufacturing processes.

Advanced manufacturing technology of high silicon aluminum alloys has been identified as one of the manufacturing processes most in need of new developments to obtain the required improvements for a new generation of vehicles. High speed machining using cutting speeds above 5000 m/min - one order of magnitude increase over the current common practice in the automotive industry - has been highlighted as a potential solution to make this goal feasible. The elements with the most important effect on tool life and wea mechanisms are workpiece material microstructure and eventual inhomogenities, non-metallic inclusions and other hard spots, as well as the silicon content.

A positive tool geometry and sharp cutting edge are considered optimal when using PCD and/or carbide tooling and will have to be coupled with a stable, vibration-free machining system. Improving the tool holder's stiffness and minimizing tool run-out are methods also taken into account. The experimental program is focused on milling of A356, high Silicon aluminum alloy widely used in automotive industry.

Tool life and wear mechanisms and cutting force data are collected and analyzed; the effect of different cooling environment is also evaluated. Chip formation is being analyzed and the effect of process characteristics on chip formation is described. The effects of machining parameters on workpiece surface quality are also considered.

High speed milling tests were performed in two separate stages: (1) Milling of solid block / continuous surface castings of A356 alloy at cutting speeds of up to 7000 m/min; and (2) Milling of engine block segments /interrupted surface castings, at cutting speeds of up to 5,000 m/min.

a) The milling tests on solid surface castings were performed initially at a fixed cutting speed of 5225 m/min using uncoated and diamond coated carbide inserts and three different coolant environments: dry, MQL and flood coolant. Based on the positive results obtained, at 5225 m/min, the cutting velocity was tentatively increased to 7,000 m/min.

b) Milling tests on engine block segments

This experimental investigation explored the effect of an actual part surfaces and thickness discontinuities on the performance of the tool at the optimized cutting parameters obtained in the previous stage. Cutting speeds of 2,000 to 5,000 m/min were used. Owning to the fact that no severe detrimental effect of cutting speed on tool wear mechanisms or part surface quality was recorded, it can be concluded that the higher cutting speed range is a viable option that merits further investigation.

Speaker Biography

Ms. Mihaela (Miky)Dumitrescu obtained her B.Sc. degree in 1988 from "Transylvania University" in Brasov, Romania, and her M.Eng. degree in 1998, from McMaster University in Hamilton, ON. She is a research engineer with the McMaster Manufacturing Research Institute, and her areas of interest include high speed machining of difficult to cut materials, optimization of very high speed machining of aluminum alloys and LASER assisted machining processes. She is also involved in process and tooling optimization studies for different manufacturing processes. She has 14 journal and conference publications outlining aspects of her research work.

1:45PM Finite Element Modeling for Machinability Aspects of Aluminum Alloys

Dr. Eugene Ng
McMaster University, Canada

The increasing drive for improvements in performance and dimensional accuracy in automotive parts has lead to the employment of High Speed Machining (HSM) technology. Given the high volume of machining undertaken in industry, it is of significant importance to predict the nature of machining-induced residual stresses in a component based upon the machining conditions and material behaviors.

The productivity in high speed machining is hindered because of problems caused by the dynamics of tool/ workpiece/ fixture system as well as tool life. Once the chatter is eliminated, the material removal rate is constrained by the tool wear and stresses in the cutting edge, which are dependent on tool geometry, tool and workpiece material, and cutting parameters. When machining with higher cutting speed and with large flank wear length, the temperature generated along the tool/ workpiece interface increased drastically. This will usually generate unfavorable tensile residual stress in the newly machined surface. However when the tensile residual stress generated was less than 10 µm deep, the fatigue performance will not be affected or compromised. When machining aluminum alloys, the tendency for burr formation increases due to its high ductility. The size of the burr is dependent on plastic flow stress field, which is affected by the machining parameters and tool wear. The cost of removing these burrs is directly proportional to their size.

For the application described in this presentation, the selection of optimum machining parameters and tool geometry is controlled by the integrity of the surface produced, the formation of burr and part distortion. No publications were found so far on modeling the effects of flank wear length on burr height, therefore, our research work is investigating the feasibility of using finite element modeling based on an update Lagrangian formulation to model the effects of rake angles (0º and +18º) and flank wear length (0mm, 0.1mm, 0.2mm and 0.3mm) on temperature distribution, cutting forces, stress & strain distributions, residual stress and burr formation. This presentation will introduce a Finite Element method to model the residual stress and burr formation states induced by high speed machining of Aluminum alloy (6061).

The model takes into account workpiece thermo-mechanical properties, cutter geometry and flank wear length, and process parameters. The analysis is based on an updated Lagrangian finite element method using ABAQUS/Explicit™ as the solver. The modeled results show that flank wear length has a more significant effect on cutting forces and temperature, which influence the residual stress distribution beneath the machined surface. The main advantages of using finite element analysis for modeling the metal cutting process is that the workpiece material properties can be modeled as a function of temperature and strain rate and the tool/chip interface can be modeled with sticking and sliding friction conditions. The results indicate that for a flank wear greater than 0.2mm, the tensile residual stress magnitude and penetrated depth into the workpiece material increase. Also, burr height increases as the flank wear length increases depending on the rake angle used. With this analysis, we can predict when to stop using the tool based on surface integrity and the burr height criteria.

Speaker Biography

Dr. Eu-Gene Ng is a Post Doctorate fellow and research manager in MMRI. He acquired his Ph.D. from University of Birmingham, England in 2001. While pursuing his Ph.D., he has undertaken a British government/ European industry (Rolls-Royce, England; SNECMA, France) funded research program on 'High Speed Milling of Nickel Based Super Alloy'. After completion, this research was graded 5 stars by the British government. Dr. Ng's research interest includes finite element modeling, high speed machining of difficult to cut materials, acquiring material properties at high strain rates and elevated temperatures and surface integrity issues. The major contributions to his research areas include: (i) development of a finite element subroutine to determine when crack propagation will occur, (iii) finite element modeling of 3-D machining with chip segmentation and (iii) developing a protocol for modifying the residual stress distribution beneath the newly high speed machined surface from tensile to compressive without a secondary process. He has over 17 academic journal and 20 reviewed conference publications.

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Last modified: August 24, 2007 13:45:29