Metallurgy Commons^™

New Experimental Apparatus To Investigate Hot Tearing Behavior In Steel, Yanru Lu, Laura Bartlett, Ronald J. O'Malley, Semen Naumovich Lekakh, Mario F. Buchely

Materials Science and Engineering Faculty Research & Creative Works

Hot tearing is a complex thermomechanical phenomenon occurring in the semi-solid region. Strain in this region can induce cracking and localized alloying element segregation. An apparatus for investigating hot tearing was developed utilizing a servo-motor controlled cylinder to apply a pre-determined amount of strain to the solidifying shell. A special mold was developed using filling and solidification modeling to ensure that dendrite growth was perpendicular to applied strain. A computer-automated system was utilized to control the strain and strain rate and measure the force and displacement. Solidification experiments utilizing AISI 1020 steel validated the apparatus capabilities and optimized testing parameters.

The Influence Of Ti, Nb And V On The Hot Ductility Of As-Cast Microalloyed Steels, Madhuri Varadarajan, Laura Bartlett, Ronald J. O'Malley, Semen Naumovich Lekakh

Materials Science and Engineering Faculty Research & Creative Works

Microalloying with Ti, Nb and V, both individually and in combination, is a common method for producing steels with high strength and toughness. However, interaction with other elements and impurities can lead to cracking during continuous casting and rolling. The hot ductility of commercially cast V, Nb and Nb-V-Ti steels has been investigated using two experimental methods: tensile testing utilizing a servo-hydraulic load frame with a resistance furnace and thermomechanical testing using rapid joule heating. The temperature-dependent ductility of these steels is compared for both test methods. Factors that influence the ductility of these steels are discussed.

Processing And Properties Of Medium-Mn Trip Steel To Obtain A Two-Stage Trip Behavior, D. M. Field, L. G. Garza-Martinez, D. C. Van Aken

Materials Science and Engineering Faculty Research & Creative Works

Two medium-Mn steels of nominal composition 0.15C-2.0Si-10.5Mn-(0.75, 1.5) Al-0.04Nb-balFe (wt pct) were processed to produce sub-micron grain sizes of 0.65 and 0.80 μm. Mechanical testing was performed in three successive conditions: hot rolled, intercritically annealed, and cold rolled with subsequent intercritical annealing. Intercritical annealing was performed at 923 K for 20 hours. Electron-backscattered diffraction and X-ray diffraction were utilized to characterize the microstructure, consisting of α-ferrite, α-martensite, ε-martensite, and γ-austenite. Microstructural constituents were tracked during tensile deformation, and it was found that both steels exhibited two-stage TRIP with γ-austenite martensitically transforming first to ε-martensite and as strain increased ε-martensite transformed …

A Spatially Distributed Fiber-Optic Temperature Sensor For Applications In The Steel Industry, Muhammad Roman, Damilola Balogun, Yiyang Zuang, Rex E. Gerald Ii, Laura Bartlett, Ronald J. O'Malley, Jie Huang

Materials Science and Engineering Faculty Research & Creative Works

This paper presents a spatially distributed fiber-optic sensor system designed for demanding applications, like temperature measurements in the steel industry. The sensor system employed optical frequency domain reflectometry (OFDR) to interrogate Rayleigh backscattering signals in single-mode optical fibers. Temperature measurements employing the OFDR system were compared with conventional thermocouple measurements, accentuating the spatially distributed sensing capability of the fiber-optic system. Experiments were designed and conducted to test the spatial thermal mapping capability of the fiber-optic temperature measurement system. Experimental simulations provided evidence that the optical fiber system could resolve closely spaced temperature features, due to the high spatial resolution and …

Spherical Cavity Expansion Approach For The Study Of Rigid-Penetrator’S Impact Problems, Mario Buchely, Alejandro Marañon

Materials Science and Engineering Faculty Research & Creative Works

In recent years, Spherical Cavity Expansion (SCE) theory has been extensively utilized to model dynamic deformation processes related to indentation and penetration problems in many fields. In this review, the SCE theory is introduced by explaining the different mathematical features of this theory, its solution, and a potential application to model the penetration of a rigid penetrator into a deformable target. First, a chronologically literature review of the most common models used to study this kind of penetration problems is introduced, focusing on the SCE theory. Then, the engineering model of penetration is presented using the SCE approach. The model …

Modeling Of Scrap Dissolution In Molten Iron For The Case Of Heat Transfer-Controlled Process By Different Approaches And Comparison Of Their Accuracies, Ajay Kumar Shukla, Brahma Deo, D. G.C. Robertson

Materials Science and Engineering Faculty Research & Creative Works

Dissolution of steel scrap in molten iron is studied by using analytical as well as numerical approaches for the case of a heat transfer-controlled process. The approaches used are Green's function approach, quasi-static approach, integral profile method (IPM) (with parabolic profile), and finite difference methods (FDM). Application of FDM explicit and FDM implicit with fixed grid and variable grid is described. Accuracy of all the approaches is compared in terms of total dissolution time evaluated from overall heat balance criterion. The selection rule of time step and deciding the suitable approach for achieving minimum error for different operating conditions, represented …

Aging Response On The Stress Corrosion Cracking Behavior Of Wrought Precipitation-Hardened Magnesium Alloy, G. R. Argade, S. K. Panigrahi, R. S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

Constant immersion testing and slow strain rate testing (SSRT) are conducted on wrought magnesium alloy in a 3.5 wt.% NaCl solution. After solution annealing (SA) at 525 °C for 8 h, the alloy was isothermally aged at 210 °C for 15 h, 48 h, and 144 h to obtain underaged (UA), peak-aged (PA), and overaged (OA) microstructures, respectively. After 32 days of constant exposure in chloride solution, the SA and UA samples showed the lowest (~ 0.10 mg cm−2 day−1) and the highest (~ 0.20 mg cm−2 day−1) weight loss, respectively. SSRT was carried out at an initial strain rate …

Grain Size Effects In Selective Laser Melted Fe-Co-2v, Wesley Everhart, Joseph William Newkirk

Materials Science and Engineering Faculty Research & Creative Works

The material science of additive manufacturing (AM) has become a significant topic due to the unique way in which the material and geometry are created simultaneously. Major areas of research within inorganic materials include traditional structural materials, shape memory alloys, amorphous materials, and some new work in intermetallics. The unique thermal profiles created during selective laser melting (SLM) may provide new opportunities for processing intermetallics to improve mechanical and magnetic performance. A parameter set for the production of Fe-Co-2V material with additive manufacturing is developed and efforts are made to compare the traditional wrought alloy to the AM version of …

Elevated Temperature Mechanical And Microstructural Characterization Of Slm Ss304l, G. R. Hecht, Sriram Praneeth Isanaka, Joseph William Newkirk

Materials Science and Engineering Faculty Research & Creative Works

SLM built SS304L was annealed and water quenched to minimize residual stress and avoid carbide precipitation. Mini-tensile characterization of strength and elongation at temperature conditions up to 800°C, along with observations of the associated microstructural transformations were utilized to understand the changes produced in SLM SS304L. As-built and annealed specimens were found to exhibit decreasing strength and elongation with increasing temperature as expected. Carbide precipitates appeared after short times at high temperatures within both as-built and annealed specimens for all cases, but no brittle intermetallic phase development was observed for any of the temperatures investigated. While the lack of Sigma, …

Compressive And Bending Performance Of Selectively Laser Melted Alsi10mg Structures, D. Murphy, O. Fashanu, Myranda Spratt, Joseph William Newkirk, K. Chandrashekhara, H. Misak, D. Klenosky

Materials Science and Engineering Faculty Research & Creative Works

Selective laser melting (SLM) is a widely used additive manufacturing technique that effectively manufactures complex geometries such as cellular structures. However, challenges such as anisotropy and mechanical property variation are commonly found due to process parameters. In a bid to utilize this method for the commercial production of cellular structures, it is important to understand the behavior of a material under different loading conditions. In this work, the behavior of additively manufactured AlSi10Mg under compression, bending, and tension loads was investigated. Vertical and horizontal build directions are compared for each type of loading. Specimens were manufactured using the reduced build …

Comparison Of Fatigue Performance Between Additively Manufactured And Wrought 304l Stainless Steel Using A Novel Fatigue Test Setup, M. M. Parvez, Y. Chen, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

In this research, a novel adaptive controlled fatigue testing machine was designed for bending type high cycle fatigue test. A unique dual gauge section Krouse type mini specimen was designed for simply supported transverse bending. Displacement controlled fatigue tests were implemented using an electromechanical actuator. The variation in the control signal and load observed during the test provides unique insights into realizing the deterioration of the specimen due to fatigue. These analyses were utilized to compare the fatigue performance of wrought and additively manufactured 304L stainless steel. The influence of the build direction on fatigue performance was also investigated by …

Effective Elastic Properties Of Additively Manufactured Metallic Lattice Structures: Unit-Cell Modeling, Okanmisope Fashanu, David Murphy, Myranda Spratt, Joseph William Newkirk, K. Chandrashekhara, Ben Brown, John Porter

Materials Science and Engineering Faculty Research & Creative Works

Lattice structures are lightweight materials, which exhibit a unique combination of properties such as air and water permeability, energy and acoustic absorption, low thermal conductivity, and electrical insulation. In this work, unit-cell homogenization was used to predict the effective elastic moduli of octet-truss (OT) lattice structures manufactured using selective laser melting (SLM). OT structures were manufactured using a Renishaw AM 250 SLM machine with various relative densities. Compression test was carried out at strain rate 5 x 10^-3 m^-1 using an MTS frame. Finite element analysis was used in the determination of the OT’s effective elastic properties. Results …

Mechanical Properties Of Heusler Alloys, Wesley Everhart, Joseph William Newkirk

Materials Science and Engineering Faculty Research & Creative Works

Heusler alloys have been a significant topic of research due to their unique electronic structure, which exhibits half-metallicity, and a wide variety of properties such as magneto-calorics, thermoelectrics, and magnetic shape memory effects. As the maturity of these materials grows and commercial applications become more near-term, the mechanical properties of these materials become an important factor to both their processing as well as their final use. Very few studies have experimentally investigated mechanical properties, but those that exist are reviewed within the context of their magnetic performance and application space with specific focus on elastic properties, hardness and strength, and …

On The Feasibility Of Tailoring Copper-Nickel Functionally Graded Materials Fabricated Through Laser Metal Deposition, Sreekar Karnati, Yunlu Zhang, Frank W. Liou, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this study, pulse‐width modulation of laser power was identified as a feasible means for varying the chemical gradient in copper—nickel‐graded materials. Graded material deposits of 70 wt. %. copper‐30 wt. %. nickel on 100 wt. %. nickel and vice versa were deposited and characterized. The 70/30 copper—nickel weight ratio in the feedstock powder was achieved through blending elemental copper and 96 wt. %. Ni—Delero‐22 alloy. At the dissimilar material interface over the course of four layers, the duty cycle of power was ramped down from a high value to optimized deposition conditions. This change was theorized to influence the …

Development Of Castrip Dual Phase Steel, Brenton Allen Hrebec

Masters Theses

“Thermomechanical processing necessary to produce DP 980 steel using CASTRIP hot band was investigated. The resultant steel has an ultimate tensile strength of 1038 MPa, yield strength of 744 MPa, and total elongation of 8.6%. These mechanical properties were achieved by batch annealing the hot band at 649°C for 48 hours and cold rolling to a 20% reduction. The steel was continuously annealed to simulate a galvanization cycle with an intercritical temperature of 810°C. The possibility of improving the texture of the steel by warm rolling under dynamic strain aging conditions was investigated. Dynamic strain aging in the CASTRIP hot …

Oxide Inclusion Evolution And Factors That Influence Their Size And Morphology, Obinna M. Adaba

Doctoral Dissertations

"The evolution of oxide inclusion size distribution and the shape of the distribution during steelmaking and casting and the process variables that influence the inclusion characteristics at different stages were investigated and documented. A statistical method for transforming the 2D size distribution to their actual 3D distributions and the application of a kinetic model to determine nucleation and growth mechanisms were tested. Finally, laboratory experiments were performed to study the effects of preexisting inclusions, steel active oxygen content, and supersaturation on the size and morphology of Al₂O₃ inclusions.

The inclusion size, composition, and morphology following steel deoxidation …

Development Of Stage-I Tempered High Strength Cast Steel For Ground Engaging Tools, Viraj Ashok Athavale

Doctoral Dissertations

"Ground Engaging Tools (GET) are the expendable replacement parts used in heavy machinery used with mining or construction equipment. GET’s protect the expensive machine components from the wear and tear found common in high-impact or high-abrasion environments. The goal of this project is to develop advanced next-generation alloy choices that outperforms the existing GET materials. A method of predicting tempered hardness of mixed microstructures was formulated. Using this model, two alloy series viz. Cr-Ni-Mo and Mn-Si-Mo-V were proposed and experimented with the goal of obtaining a high strength and impact resistant cast steel. Cast iterations of Cr-Ni-Mo alloy series were …

Effect Of Wall Thickness And Build Quality On The Compressive Properties Of 304l Thin-Walled Structures Fabricated By Slm, Myranda Spratt, Sudharshan Anandan, Rafid M. Hussein, Joseph William Newkirk, K. Chandrashekhara, Heath Misak, Michael Walker

Materials Science and Engineering Faculty Research & Creative Works

The specific strength of lightweight lattice structures built with SLM is of interest to the aerospace industry. Honeycombs were manufactured with increasing wall thicknesses (which increases density) and tested under compression. The optimal strength to density ratio was determined from the resulting data. The build quality was also evaluated to determine how/if the results were influenced by the specimen quality. Differences between the nominal and as-built geometry were identified, but considered to be minimal. Microstructural evaluation of the specimens revealed a possible dependence on the ‘border scan’ properties, as the thickness of the specimens was such that the board scan …

Fast Prediction Of Thermal History In Large-Scale Parts Fabricated Via A Laser Metal Deposition Process, Lei Yan, Tan Pan, Joseph William Newkirk, Frank W. Liou, Eric E. Thomas, Andrew H. Baker, James B. Castle

Materials Science and Engineering Faculty Research & Creative Works

Laser metal deposition (LMD) has become a popular choice for the fabrication of near-net shape complex parts. Plastic deformation and residual stresses are common phenomena that are generated from the intrinsic large thermal gradients and high cooling rates in the process. Finite element analysis (FEA) is often used to predict the transient thermal cycle and optimize processing parameters; however, the process of predicting the thermal history in the LMD process with the FEA method is usually time-consuming, especially for large-scale parts. Herein, multiple 3D FEA models with simple assumptions on the heat source and its loading methods are compared and …

Development Of An Engineering Diagram For Additively Manufactured Austenitic Stainless Steel Alloys, Zachary T. Hilton, Joseph William Newkirk, Ronald J. O'Malley

Materials Science and Engineering Faculty Research & Creative Works

Austenitic stainless steels are the most widely applied types of stainless steels, due to their good weldability and high corrosion resistance. A number of engineering diagrams exist for the purpose of providing insight into the behavior of these steels. Examples of these diagrams are constitution diagrams (aka Schaeffler Diagrams) which are used to approximate the solidification path of the alloy and the amount of retained ferrite in the solidified matrix. Other diagrams are the Suutala diagram, which approximates cracking susceptibility, and microstructural maps, which predict the solidification path by varying a processing parameter, such as cooling rate. By combining these …

Modeling And Simulation Of Mass Flow Of Steel Plate/Slab During Hot Rolling, X. Wang, S. Ganguly, K. Chandrashekhara, Mario F. Buchely, Semen Naumovich Lekakh, David C. Van Aken, Ronald J. O'Malley, D. Bai, Y. Wang, T. Natarajan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The ability to predict mass flow behavior during hot rolling is essential to product quality. In this study, viscoplastic models of the steels from SSAB and U.S. Steel were developed based on experimental stress-strain curves. A three-dimensional nonlinear finite element model was built to simulate a reverse plate hot rolling and a hot strip rolling process. For plate rolling, a seven pass schedule was simulated. The plastic strain distributions during rolling were investigated. The results show that the surface of the plate has larger plastic strain than the center. In the case of hot strip rolling, the simulation predicts that …

Corrosion Performance Of Zirconium-Based Passivations On Electroplated Zinc Nickel, Madison Morgan Reed

Masters Theses

“Performance requirements for Department of Defense (DoD) electrical components include corrosion and electrical contact resistance. Historically, electroplated cadmium with a chromate conversion coating (CrCC) has been used to meet corrosion and contact resistance standards. However, replacements are needed for these materials because they are toxic and carcinogenic. Electroplated γ-ZnNi has been identified as an acceptable alternative to Cd. This study evaluated commercially available Zr-based thin films and sealers as passivations for potential replacement of CrCCs. Ten different passivations were tested and compared with bare γ-ZnNi. X-Bond and Zircobond passivations were found to provide some improvement to the bare ZnNi corrosion …

Grain Refinement Of High Alloy Stainless Steels In Sand And Directionally Solidified Castings, Dustin Alan Arvola

Masters Theses

"The goal of this research project is to develop an industrially viable melting process that will control the crystallization macrostructure of austenitic grades of cast steels. Titanium nitride (TiN) has proven to be an effective grain refiner of austenite. Theoretical simulation and experimental application has led to the development of a repeatable grain refining melt process for austenitic stainless steel alloys.

Grain refinement of the as-cast structure of Cr-Ni stainless steel alloys solidified with primary FCC, BCC and dual FCC/BCC phases was studied experimentally. Refinement was achieved in both cast ferritic and austenitic grades. Dual solidification of …

Effect Of Microstructural Features On Steel Machinability, Mark C. Emmendorfer

Masters Theses

Non-metallic inclusions can have a tremendous impact on the machinability of steel. Some oxide inclusions such as alumina, spinel, and other refractory abrasive oxide inclusions can have a detrimental effect on machinability. Modification of oxide inclusions by calcium treatment can promote the formation of low melting point oxides such as anorthite and gehlenite inclusions that can assist in chip formation and form a lubricating layer on the rake surface of the machine tool. MnS is known to be beneficial to improving the machinability of steel. They assist in chip formation by being heavily deformed in the primary shear zone. Sulfide …

Effect Of Thickness On The Structure And Corrosion Performance Of Sputtered Ce-Al-O Coatings On Al 2024-T3 Alloy Substrates, Yuanyuan Liu, Jiamu Huang, Lilu Qin, James B. Claypool, Matthew J. O'Keefe, Yiming Jiang

Materials Science and Engineering Faculty Research & Creative Works

Ce-Al-O coatings with thicknesses between ca. 136 nm and 1094 nm were deposited on Al 2024-T3 alloy substrates using magnetron co-sputtering of independent Al and CeO2 targets. The Ce-Al-O coatings with thicknesses from ca. 136 nm to 490 nm were compact, dense, and did not have distinct X-ray diffraction peaks. The ca. 1094 nm thick Ce-Al-O coating exhibited a columnar-textured outer layer ∼700 nm thick and a dense, ∼390 nm thick inner layer. X-ray photoelectron spectroscopy analysis revealed that the Ce-Al-O coatings contained Ce (III) species, and that the Al/Ce atomic ratio decreased with increasing coating thickness. Electrochemical corrosion data …

Chemistry, Design, And Processing Of Two-Stage Trip Steel, Daniel M. Field

Doctoral Dissertations

"A regular solution model was developed to calculate the chemical driving force for α-martensite formation, ΔG^{λ→ α}_Chem. A model for the strain energy, ΔG^λ→α_str, was formulated utilizing the Young’s modulus (E), lattice misfit squared (δ²), and molar volume (Ω) which opposed the chemical driving force for α-martensite formation. The M^α_S was determined at a temperature at which ΔG^λ→α_Chem + ΔG^λ→α_str = 0. In conjunction with a previously developed ε-martensite model, a means of predicting the volume fraction of λ-austenite was determined; and it was shown that for values …

Micro-Slotting Technique For Measurement Of Local Residual Stress In Metallic Materials, Elizabeth Anne Burns

Doctoral Dissertations

"Micro-slotting, a micro-scale relaxation residual stress measurement technique, has been shown in recent years to be a reliable method for measuring local residual stresses in metallic materials. This technique employs an SEM-focused ion beam system for milling and imaging, digital image correlation software to track displacements due to residual stress relaxation, and finite element analysis for interpolation of the original local stress state. In this research, a micro-slotting procedure was established using finite element models and was used to obtain sub-surface residual stress measurements on machined and shot peened planar Ti-6Al-4V samples. These measurements were compared to macro-scale XRD residual …

Design And Fabrication Of Functionally Graded Material From Ti To Γ-Tial By Laser Metal Deposition, Xueyang Chen, Lei Yan, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

Functionally graded material (FGM) is one kind of advanced material characterized by a gradual change in properties as the position varies. The spatial variation of compositional and microstructure over volume is aimed to control corresponding functional properties. In this research, when 100% γ-TiAl was directly deposited on pure Ti substrate, cracks were formed within the γ-TiAl layer. Then a six-layer crack-free functionally graded material of Ti/TiAl was designed and fabricated by laser metal deposition (LMD) method, with composition changing from pure Ti on one side to 100% γ-TiAl on the other side. The fabricated FGM was characterized for material properties …

Influence Of Gage Length On Miniature Tensile Characterization Of Powder Bed Fabricated 304l Stainless Steel, Sreekar Karnati, Jack L. Hoerchler, Frank W. Liou, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Miniature tensile specimens with varying aspect ratios were fabricated from 304L stainless steel (SS) made using powder bed additive manufacturing (AM) process. The tensile characteristics measured from these specimens were analyzed to assess the impact of gage length. The study found no impact upon varying gage length on yield and ultimate strength measurements. However, a significant impact was observed on strain measurements. This data was also used to perform Weibull statistics to estimate the stochastic performance of the material. Fractography was performed to visually identify the types of flaws. A comparative study with specimens fabricated from cold rolled annealed 304 …

Characterization Of Heat-Affected Powder Generated During Selective Laser Melting Of 304l Stainless Steel Powder, Austin T. Sutton, Caitlin S. Kriewall, Ming-Chuan Leu, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The selective laser melting (SLM) process is an Additive Manufacturing (AM) technique that uses a laser to fuse successive layers of powder into near fully dense components. Due to the large energy input from the laser during processing, vaporization and instabilities in the melt pool occur causing the formation of condensate and laser spatter, collectively known as heat-affected powder. Since heat-affected powder settles into the powder bed, the properties of the unconsolidated powder may be altered compromising its reusability. In this study, characterization of 304L heat-affected powder was performed through particle size distribution measurements, x-ray diffraction, metallography, energy-dispersive spectroscopy mapping, …