Light Metal Technology: Light Metal Technology
Sponsored by: TMS: Composite Materials Committee
Program Organizers: Xiaoming Wang, Purdue University; Peng Cao, The University of Auckland

Tuesday 9:20 AM
October 11, 2022
Room: 402
Location: David L. Lawrence Convention Center

Session Chair: Christopher Rudolf, US Naval Research Laboratory


9:20 AM  
Dielectric Behavior of Aluminum and Its Relevance to Electrical Conduction and Stress/Strain Self-sensing: Deborah Chung1; Xiang Xi1; 1State University of New York Buffalo
    Aluminum is a lightweight electrical conductor. Although the conduction behavior is well-known, the dielectric (polarization) behavior is not. The polarization stems from the interaction of the free (valence) electrons with the atoms. It gives a voltage that impedes conduction. The resulting increase in the apparent resistivity degrades the conduction performance. In addition, the capacitance resulting from the polarization delays the signal propagation (RC time constant). The capacitance relates to the permittivity (a material property), which is high (54,800, 2 kHz). Although the resistance is not affected by bending, the capacitance is reduced by bending. Upon bending back to the original straight shape, the capacitance is approximately restored for a single bend with various radii of curvature, but it is only partially restored for multiple bends. Bending degrades the dielectric connectivity (dipole-dipole interaction). The capacitance increases monotonically and reversibly with increasing tensile stress (elastic regime), thereby allowing capacitance-based stress/strain self-sensing.

9:40 AM  
Revealing Growth Mechanisms of Faceted Al2Cu Intermetallic Compounds via High-speed Synchrotron X-ray Tomography: Zihan Song1; Oxana Magdysyuk2; Tay Sparks1; Yu-Lung Chiu1; Biao Cai1; 1University of Birmingham; 2Diamond Light Source Ltd
    High-speed synchrotron X-ray tomography to image the growth of Al2Cu intermetallic compounds in 4D (3D plus time) during solidification of Al-45wt%Cu alloy. Two categories of growth patterns (basic units and dendrites) are identified. Basic units are elongated rods whose cross-section are L, U or hollow-rectangular shapes. The transition from L pattern to U and finally to hollow-rectangular shaped morphology was observed. Faceted dendritic patterns include equiaxed prism and columnar dendrites. Self-repeated layer-by-layer stacking of the basic units is proposed as a governing mechanism for the growth of Al2Cu faceted dendrites. Furthermore, when rotating Al-45wt%Cu during upwards directional solidification, under a transverse magnetic field of 0.5T, highly refined and well aligned Al2Cu intermetallic compounds are obtained. This is attributed to a rotational stirring flow that modulates and regulates the temperature and solute distribution. The developed experimental findings provide a physical understanding of the formation of faceted intermetallic compounds during solidification.

10:00 AM Break

10:20 AM  
Towards Light Weight Structural Materials-optimized Processing of Nanocrystalline Mg-Al Alloys: Mohammad Umar Farooq Khan1; Taban Larimian2; Tushar Borkar2; Rajeev Gupta3; 1Texas A&M University; 2Cleveland State University; 3North Carolina State University
    In this work Mg-x wt.% Al alloys were produced by high energy ball milling (HEBM) and consolidated using spark plasma sintering. Hardness, microstructure, and phase analysis for the alloys were investigated using Vickers’ micro-indenter, scanning electron microscopy, and X-ray diffraction, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy studies were done using a potentiostat in 0.1 M NaCl and 0.1 M Na2SO4, respectively, at ambient temperature. The hardness increased with an increase in the Al content even though the grain size increased, which correlates with various strengthening contributions from Al addition. The corrosion behavior improved on Al addition up to 10 wt.% and deteriorated for higher Al content. The corrosion behavior will be discussed based on microstructural changes Present work is valuable in designing the Mg-Al based alloys produced by HEBM with enhanced strength and corrosion resistance.

10:40 AM  
Precipitation Hardening on Fracture Behavior of Extruded Mg10Gd Modified with Nd and La: Petra Maier1; Norbert Hort2; 1University of Applied Sciences Stralsund; 2Helmholtz-Zentrum Hereon
    This study is a follow up on investing the influence of adding Nd and La to extruded Mg10Gd on mechanical properties. Previous research showed that an increase in tensile strength by decreasing grain size and increasing volume fraction of RE-rich precipitates with increasing the amount of alloying elements. The alloys containing La appeared less ductile in 3-point-bending tests. Precipitation hardening caused strong grain growth, most significant in Mg10Gd – resulting in half the outer-strain value to crack initiation. Alloys containing Nd showed a precipitation hardening response, but the increase in strength was on the expense of ductility, here fractography reveals the highest amount of large cleavage planes. Crack propagation in Mg10Gd alloy is mostly driven by twinning. Increased amount and size of second phases by addition of Nd and La suppress twinning, but the crack initiation and propagation is caused by brittle, coarse second phases, mostly in alloys containing La.

11:00 AM  
An Innovative Experimental Setup for the Electro-thermo-mechanical Characterization of Microscale Ti-6Al-4V Wires: Won June Choi1; Maxwell Kulak1; Chunghwan Kim1; Eric Payton2; Christopher Rudolf3; Wonmo Kang1; 1Arizona State University; 2Air Force Research Laboratory; 3Naval Research Laboratory
    In this study, we investigate electroplasticity in Ti-6Al-4V wires, i.e., the mechanism(s) of material deformation under concurrent mechanical and electrical load. An innovative force-controlled tensile tester, consisting of an electronic balance, piezo actuator, optical camera, infrared thermometer, and electric power supply, has been developed and utilized for the electro-thermo-mechanical characterization of fine wires. Ti-6Al-4V wires with 100-μm diameter have been selected to minimize the thermal effect associated with intrinsic Joule heating. Significantly reduced thermal effect has been validated by directly comparing experimentally measured temperatures using a non-contact IR thermometer to numerically predicted temperature profiles. Our experiments indicate that applied electrical current in a range of 0–20 A/mm2 results in reduction in yield strength and failure strain of the wire as well as the brittle-to-ductile transition. The observed changes in mechanical responses of Ti-6Al-4V wires match well with previous reported thermo-mechanical results, indicating that the thermal effect is still dominant.

11:20 AM  
Residual Stresses in Multilayer Metal Sheets Produced by the Friction Assisted Lateral Extrusion Process: Claire Adams1; Máté Sepsi2; David Field1; Laszlo Toth3; 1Washington State University; 2University of Miskolc; 3Université de Lorraine
    Ultrafine grained materials can be produced through severe plastic deformation methods such as the friction assisted lateral extrusion process (FALEP). By FALEP, one can bond different metals into a layered-sheet and obtain lighter structures with new properties. Such multilayer structure has residual stresses which can influence fatigue strength and formability of the material. FALEP experiments were carried out on Al-1050 and Al 5052 alloys, as well as on Al-1050 and copper. The residual stresses were measured by X-ray, using the Debye ring technique and were related to the parameters of the materials and processing technique.