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SEMINAR NOTICE: Andrea Hodge, USC, Fri. 4/19/13, 3:30 pm, ARMS 1010
by Stacey, Lisa A 15 Apr '13

15 Apr '13

Please see attached Seminar Announcement for Dave Bahr's guest, Andrea Hodge from USC next Friday, April 19th. Thank you, Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: CORRECTED SEMINAR NOTICE: S. Sailei, PhD Final Exam, Thursday, 4/18/13, 9:30 am, FRNY B124
by Stacey, Lisa A 11 Apr '13

11 Apr '13

Please see notice below - note the location & corrected day (Thursday, April 18th): MATERIALS SCIENCE AND ENGINEERING SEMINAR Macrosegregation and Shrinkage Pipe Formation in Static Castings By: Sailei Zhang Ph.D. Final Examination Co-Advisors: Prof. M. J. Krane and Prof. D. R. Johnson ABSTRACT Both macrosegregation and shrinkage defects are common problems in static castings. However these two aspects were usually studied separately in earlier research. In this presentation, a single-domain multi-phase model is developed for macrosegregation evolution and shrinkage pipe formation in static castings, as functions of buoyancy- and shrinkage-induced flow. Using a volume-of-fluid (VOF) method, both the air/liquid and air/solid interfaces are tracked during shrinkage pipe formation. The model is applied to binary Ti-48Al (at.%) and ternary Ti-46.6Al-8.6Nb (at.%) alloys in a cylindrical mould (R = 3.5 cm, H = 15 cm). Experiments to investigate macrosegregation and shrinkage pipe formation are performed by casting both alloys in an induction skull melting (ISM) furnace, using tilt-casting method in investment moulds. No significant exchange of fluid that is not at nominal composition between the riser and the part is found. However, the macrosegregation level is increased in a larger scale casting (R = 30 cm, H = 50 cm), which can potentially change the primary solidification phase and the local microstructure of the γ-TiAl alloy in the final cast. To study the influence of the riser on flow exchange between riser and cast part as well as the macrosegregation development in static castings, an Al-5wt. % Cu alloy system is used. An ingot with the riser designed based on Chvorinov's rule is performed in a slab mould, which is used as a standard case for this study. The results show that a wider riser is able to provide a barrier and prevent the solute-rich interdendritic liquid in the riser from flowing into cast part. For the castings with the riser shape being fixed, the average composition in the cast part is smaller at a higher solidification rate. Date: Thursday, April 18, 2013 Time: 9:30 A.M. Place: FRNY B124 Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: SEMINAR NOTICE: S. Sailei, PhD Final Exam, Friday, 4/18/13, 9:30 am, FRNY B124
by Stacey, Lisa A 11 Apr '13

11 Apr '13

Please see notice below - note the location: MATERIALS SCIENCE AND ENGINEERING SEMINAR Macrosegregation and Shrinkage Pipe Formation in Static Castings By: Sailei Zhang Ph.D. Final Examination Co-Advisors: Prof. M. J. Krane and Prof. D. R. Johnson ABSTRACT Both macrosegregation and shrinkage defects are common problems in static castings. However these two aspects were usually studied separately in earlier research. In this presentation, a single-domain multi-phase model is developed for macrosegregation evolution and shrinkage pipe formation in static castings, as functions of buoyancy- and shrinkage-induced flow. Using a volume-of-fluid (VOF) method, both the air/liquid and air/solid interfaces are tracked during shrinkage pipe formation. The model is applied to binary Ti-48Al (at.%) and ternary Ti-46.6Al-8.6Nb (at.%) alloys in a cylindrical mould (R = 3.5 cm, H = 15 cm). Experiments to investigate macrosegregation and shrinkage pipe formation are performed by casting both alloys in an induction skull melting (ISM) furnace, using tilt-casting method in investment moulds. No significant exchange of fluid that is not at nominal composition between the riser and the part is found. However, the macrosegregation level is increased in a larger scale casting (R = 30 cm, H = 50 cm), which can potentially change the primary solidification phase and the local microstructure of the γ-TiAl alloy in the final cast. To study the influence of the riser on flow exchange between riser and cast part as well as the macrosegregation development in static castings, an Al-5wt. % Cu alloy system is used. An ingot with the riser designed based on Chvorinov's rule is performed in a slab mould, which is used as a standard case for this study. The results show that a wider riser is able to provide a barrier and prevent the solute-rich interdendritic liquid in the riser from flowing into cast part. For the castings with the riser shape being fixed, the average composition in the cast part is smaller at a higher solidification rate. Date: Friday, April 18, 2013 Time: 9:30 A.M. Place: FRNY B124 Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: PETER WINCHELL KEYNOTE SPEAKER SEMINAR REMINDER - Tomorrow, Friday, April 12th, 3:30 pm, ARMS 1010
by Stacey, Lisa A 11 Apr '13

11 Apr '13

Reminder please see seminar notice below for our Peter G. Winchell Lecture Series Keynote Speaker: Prof. Christoph Beckermann. [cid:image001.png@01CE36D3.ABBD1CA0] Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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FW: SEMINAR REMINDER: S. Lawrence, PhD Prelim I, Fri., 4/12/13, 11:30 am, ARMS 1028
by Stacey, Lisa A 11 Apr '13

11 Apr '13

Please see seminar notice below: MATERIALS SCIENCE AND ENGINEERING SEMINAR Mechanisms of Hydrogen Degradation in Metals By: Samantha Lawrence Ph.D. Prelim Exam – Part I Advisor: Prof. D. F. Bahr ABSTRACT Hydrogen is an important energy carrier; however, there are substantial barriers to effective hydrogen transport and storage. Degradation of metallic systems exposed to hydrogen (especially those used in pressure vessels, tanks, and pipelines of various energy industries) leading to unexpected catastrophic failures is particularly disturbing. Hydrogen is linked to a decrease in ductility, fracture strength, and fracture toughness in many metals (the phenomenon of hydrogen embrittlement). Three broadly grouped degradation mechanisms have been identified: (1) hydride formation, where brittle hydride precipitates ease fracture by providing low energy crack paths; (2) hydrogen-enhanced localized plasticity (HELP), where localized deformation increases in the presence of hydrogen due to a decrease in barriers to dislocation motion; and (3) hydrogen-enhanced decohesion (HEDE), where hydrogen reduces interfacial atomic bond strengths resulting in a sharp transition between ductile and brittle fracture. Hydrogen diffusion and subsequent capture at microstructural inhomogeneities, or traps, is required to establish a critical H-concentration prior to failure. Realizing that a “one‑size‑fits‑all” mechanism explaining observations of hydrogen embrittlement is unlikely, proposed degradation mechanisms are presented and future work geared toward understanding the interrelationships between the mechanisms is proposed. Date: Friday, April 12, 2013 Time: 11:30 A.M. Place: ARMS 1028 Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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Fwd: PPDA April 2013 Newsletter
by Donna Bystrom 11 Apr '13

11 Apr '13

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FW: SEMINAR REMINDER, K. Fezi, MS Final Exam, Thur. 4/11, 1:30 pm, ARMS 1103
by Stacey, Lisa A 10 Apr '13

10 Apr '13

Please see seminar notice below: MATERIALS SCIENCE AND ENGINEERING SEMINAR Modeling of Transport Phenomena During Electroslag Remelting of Alloy 625 By: Kyle S. Fezi Master of Science Final Examination Advisor: Prof. M. J. M. Krane ABSTRACT A numerical model is used to examine the transport phenomena during Electroslag Remelting (ESR), primarily the phenomenon of macrosegregation. Another model has been developed to study morphological effects on macrosegregation during the ESR process, including grain growth kinetics and solid grain movement. Both models are built on an existing model that is capable of solving mass, momentum, species, and energy conservation equations during multicomponent solidification. ESR is a secondary melting process used to enhance the metallurgical structure and refine the chemistry of an ingot. ESR consists of passing an alternating current through a consumable electrode immersed in an electrically resistive slag that generates enough heat to melt the electrode. There are limitations for ESR due to an increase in segregation levels with ingot diameter. In order to produce larger ingots than current practice, several constant current ESR runs are simulated to explain possible ways to minimize the segregation levels. Low currents are found to decrease the segregation level as well as shifting the initial composition to decrease the solutal buoyancy force. The columnar-to-equiaxed transition model is used to examine the effect of having free-floating equiaxed grains in the center of a casting. The CET is shifted by changing the thermal boundary conditions, the free-floating equiaxed particle diameter, and the possible number of heterogeneous nucleation sites. Comparisons are drawn between the static castings of the CET model and the ESR ingots. Date: Thursday, April 11, 2013 Time: 1:30 P.M. Place: ARMS 1103 Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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Fwd ME seminar
by Donna Bystrom 10 Apr '13

10 Apr '13

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FW: SEMINAR REMINDER: M. Dubelman-PhD Final, Tue. 4/9/13, 9:00 am, HAMP 1113
by Stacey, Lisa A 09 Apr '13

09 Apr '13

Please see seminar reminder below (note the location in HAMP): MATERIALS SCIENCE AND ENGINEERING SEMINAR Domain Evolution in Lead-Free Thin Film Piezoelectric Ceramics By: Meredith E. Dubelman Ph.D. Final Examination Advisor: Prof. J. Blendell ABSTRACT Due to environmental and health concerns lead-free piezoelectric systems are currently being evaluated for use as replacements for lead-based ceramics. Sodium Bismuth Titanate, Na0.5Bi0.5TiO3 (NBT) - based materials offer possible alternatives. NBT is a perovskite-type, ABO3, compound and is ferroelectric at room temperature. It has a relatively high Curie temperature, a large remnant polarization, and a high coercive field at room temperature. NBT can be modified by additives, such as BaTiO3 (BT), to improve its properties further. NBT-xBT was originally reported to have a morphotropic phase boundary which lies at x = 0.06. The structure transforms from rhombohedral for x < 0.06 to tetragonal for x > 0.06. However, recent studies have shown that for some compositions NBT-xBT develop a relaxor phase at room temperature. NBT xBT materials in the compositional range between 0.05 ≤ x ≤ 0.11have been shown to contain nanodomains embedded in a non-polar cubic matrix. The fluctuations of these nanodomains give rise to the relaxor behavior which in some cases is referred to as "relaxor antiferroelectric". In contrast to ferroelectric materials, in relaxor ferroelectrics thermal fluctuations can cause the poled nanodomains to relax to an unpoled state. It is necessary to understand local structure effects on the piezoelectric response at the grain level in order to develop materials with improved performance. Using Piezoresponse Force Microscopy (PFM), this study examines the domain motion within individual grains and domain evolution over time under locally applied electric fields as well as single-point hysteresis loop measurements in thin film NBT and NBT-xBT. These experiments provide an understanding of the domain behavior that cannot be acquired through bulk, macroscopic measurements. Thin films are fabricated using hydrothermal deposition and pulsed laser deposition. The films are highly oriented and exhibit relaxor behavior at room temperature. Date: Tuesday, April 9, 2013 Time: 9:00 A.M. Place: HAMP 1113 Thank you, Lisa Stacey Secretary/Development Assistant Purdue University School of Materials Engineering 765/494-4100

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Fwd: PPDA Coffee Hour Friday 12:30PM
by Donna Bystrom 05 Apr '13

05 Apr '13

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