Characterization of Minerals, Metals, and Materials: Welding and Solidification
Sponsored by: TMS Extraction and Processing Division, TMS: Materials Characterization Committee
Program Organizers: Shadia Ikhmayies, Al Isra University; Bowen Li, Michigan Technological University; John Carpenter, Los Alamos National Laboratory; Jian Li, CanmetMATERIALS; Jiann-Yang Hwang, Michigan Technological University; Sergio Monteiro, Military Institute of Engineering ; Firrao Donato, Collegio Universitario, Italy; Mingming Zhang, ArcelorMittal Global R&D; Zhiwei Peng, Central South University; Juan P. Escobedo-Diaz, UNSW Australia; Chenguang Bai, Chongqing University; Eren Kalay, METU; Ramasis Goswami, Naval Research Laboratory; Jeongguk Kim, Korea Railroad Research Institute

Thursday 8:30 AM
March 2, 2017
Room: 31B
Location: San Diego Convention Ctr

Session Chair: Chenguang Bai, Chongqing University; Pasquale Spena, Free University of Bozen-Bolzano


8:30 AM  
Characterization of Explosively Bonded Interfaces for High Contaminant Sensitivity Environments: Olivia Underwood1; Jonathan Madison1; Lisa Deibler1; Jeffrey Rodelas1; 1Sandia National Laboratories
    Sandia’s Z-machine is the world’s most powerful and efficient laboratory x-ray radiation source. While minor contaminants, due to residue or debris can have significant effects on performance, a specific set of experiments utilizing explosive bonds as closure valves, require complete elimination of any opportunity for leakage. To assist, explosively bonded interfaces in 304L stainless steel are interrogated using ultrasonics, metallography, micro-computed tomography, hardness maps, and mechanical testing. Although traditional collision angle and flyer plate velocities are found to be insufficient in producing suitable results, the characterization performed has helped identify desirable parameters. Interface characteristics and feature lengths will be presented toward a discussion of maintaining hermeticity and the identification of metallurgical joining processes at play. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000

8:50 AM  
Investigation on the Local Mechanical Behavior of Laser Weldments in AHSS TWBs: Pasquale Russo Spena1; Luca Cortese2; Filippo Nalli1; Daniel Reiterer3; 1Free University of Bozen-Bolzano; 2Sapienza - Università di Roma; 3IDM Südtirol-Alto Adige
    Local elasto-plastic behavior of laser weldments of TWBs made of advanced high strength steels (AHSSs) is investigated, to be used in finite element (FE) forming simulations of TWBs. To this purpose, several micro-samples were extracted from weld seams of some TWBs of different AHSS grades, and subsequently tested using an axial machine equipped with proper micro-grips. Inverse methods, with the aid of FE analysis, where used to determine precisely the material constitutive relations of weldments in a large strain range, up to final fracture. A preliminary validation of the accuracy of the numerical simulations, which model the local behavior of seams, is also presented. Data concerning the local behavior of laser weldments can be used to properly model forming processes of TWBs made of AHSSs.

9:10 AM  
Microstructural Evolution of Porous Materials by Magnetic Freeze Casting: Pooya Niksiar1; Michael Frank2; Joanna McKittrick2; Michael Porter1; 1Department of Mechanical Engineering, Clemson University, Clemson; 2Materials Science and Engineering Program, University of California, San Diego
    External magnetic fields are applied during the process of directional solidification to control the microstructural evolution of ceramic scaffolds formed by freezing colloidal suspensions. Such porous materials typically have anisotropic microstructures composed of lamellar walls and mineral bridges connecting adjacent lamellae. Lamellar wall spacing and mineral bridge connectivity (length and thickness) are two characteristics that can be controlled during solidification and influence the mechanical properties of the scaffolds. While lamellar wall spacing primarily depends on the freezing conditions, mineral bridge connectivity is increased by increasing the magnetic field strength up to an optimum or by increasing the solidification rate which decreases the lamellar wall spacing (resulting in a higher probability of bridge formation). With increased connectivity, the strength and stiffness of the scaffolds increase when compressed parallel to the mineral bridges formed by external magnetic fields.

9:30 AM  
Mechanical Characterization of Weldment Zones of Selected Oil and Gas Pipeline Steel: Bodude Adebayo1; 1University of Lagos
    This work examines the integrity of weldment zone of an oil and gas pipeline steel used to convey petroleum products. To accomplish this in an efficient way, experiments on a variety of welding parameters were conducted on ASTM A109SCH40 steel specimen, welded by metal arc welding. Thus, the influence of welding current, arc voltage, welding speed, pipe thickness and depths of penetration on hardness and tensile properties of the pipeline steel were studied. The findings from this work shown that an increase in the welding speed at a constant arc voltage and current will lead to increase in penetration until maximum penetration is achieved. The practical implications of this research show that optimal weld penetration can be achieved under certain circumstances. Further researches are needed to explain how the weldment mechanism changes with varying welding conditions.

9:50 AM Break

10:05 AM  
Reconstruction of Solidification History from the Cast Microstructure of a Vacuum Arc Remelted Nickel Alloy 718 Ingot: Thomas Ivanoff1; Trevor Watt2; Eric Taleff1; 1University of Texas at Austin; 2Stratasys
    The solidification history of a remelted nickel alloy 718 ingot was reconstructed from dendritic microstructure data acquired by quantitative image analysis techniques. This information can potentially be used to determine how melt parameters, including melt pool profile and solidification rate, influence the solidification microstructures formed during remelting processes. The microstructure throughout two slabs, sectioned from the center of a laboratory-scale vacuum arc remelted (VAR) alloy 718 ingot, was imaged using macrophotography. Primary dendrite arm orientation (PDAO) and secondary dendrite arm spacing (SDAS) were then measured throughout each slab using particle detection and two-point correlation function analysis techniques. Melt pool profile and solidification rate were calculated from the measured PDAO and SDAS, respectively. The results of this study are expected to aid in the validation of process models used to predict solidification behavior during remelting processes.

10:25 AM  
The Effects of Refractory Element Addition on the Long Term Stability and Microstructural Characteristics of Nickel-Based Superalloys: Rasim Eris1; M. Vedat Akdeniz1; Amdulla O. Mekhrabov1; 1Novel Alloys Design and Development Laboratory (NOVALAB), Department of Metallurgical and Materials Engineering, Middle East Technical University
    The long term stability of L12 type ordered γ’ precipitates in the severe environmental conditions is deeply bound up with ordering characteristics and coherency between γ-γ’ interfaces. It is attributed that higher temperature capability can be sustained by adding distinct refractory elements since they shift phase transformation temperatures to higher level. Thus, in the current work, the effects of refractory X elements (where X= Mo, Nb, Ta and W) on the ordering characteristics, solidification structures and phase stability of the Ni0.8Al0.15X0.05 alloy systems will be presented. Furthermore, subsequent heat treatment including different aging times will be applied to determine the development of optimal coherency between constituent phases. The relationship between long term stability and microstructural characteristics of the present phases which is critical for the design and development of Nickel-based superalloys will be emphasized.

10:45 AM  
Interfacial Strength Characterization in a High-modulus Low-density Steel-based Fe-TiB2 Composite: Yizhuang Li1; Mingxin Huang1; 1The University of Hong Kong
    The titanium diboride (TiB2)-reinforced steel composite, designed for automotive applications, exhibits a combination of high isotropic Young’s modulus and low density as compared to existing advanced high strength steels (AHSS). The steel-based composite is produced by in-situ precipitation of TiB2 particles during eutectic solidification followed by hot rolling, and its microstructure displays a homogeneous distribution of both large primary TiB2 and small eutectic TiB2 particles in the ferrite matrix. Instead of interfacial debonding, particle cracking is the primary mode of damage, revealing high interfacial strength. To investigate the intrinsic interfacial strength, a hybrid method combining both nanoindentation and finite element analysis (FEA) was used. A micron-sized sample containing a single crystal TiB2 attaching to the ferrite matrix was fabricated by focused iron beam (FIB), and was compressed using nanoindentation with a flat indentation tip. By combining the compression and FEA results, the interfacial strength was determined.