Late News Poster Session: Physical Metallurgy
Program Organizers: TMS Administration
Tuesday 5:30 PM
March 1, 2022
Room: Exhibit Hall C
Location: Anaheim Convention Center
Cancelled
O-40: Effects of Alloying Elements on Stability of γ”-Ni3Nb Phase in Nickel Based Alloy: Kako Tokutomi1; Satoru Kobayashi1; 1Tokyo Institute of Technology
γ”-Ni3Nb(D022), the strengthening phase in Alloy718 type Nickel based alloys, is known to transform to its stable form, δ-Ni3Nb(D0a), resulting in a loss of strength. We found that the stability of γ” phase is improved by a substitution of Ta for Nb. In the present work, we show effects of Ta and Ta+V substitution on the stability of the γ”-Ni3Nb phase using diffusion-multiple type combinatorial samples and conventional bulk alloy samples. The results will be discussed in term of the diffusion coefficient of the alloying element in γ-Ni matrix and the driving force from the γ” phase to the δ phase.
O-41: Fe-rich Metastable Multi-principal Element Alloys: James Frishkoff1; Nathan Brown1; Madeline Rivera1; Amy Clarke1; Kester Clarke1; 1Colorado School of Mines
Metastable dual-phase multi-principal element alloys (DP-MPEAs) have been shown to exhibit both transformation and twinning induced plasticity (TRIP/TWIP), which contribute to characteristically high ultimate tensile strength (≥ 1GPa) and ductility (≥ 50% strain to fracture). A multi-factor thermodynamic & experimental screening approach for identifying new Fe-rich metastable DP-MPEA compositions with improved yield strength is reported here. Alloy design criteria include the elimination of cobalt, precipitate strengthening behavior, and dual-phase microstructures. The screening approach employs a novel phase metastability criterion to predict the transformation-induced plasticity susceptibility of each composition. Microstructures and tensile properties are assessed in the as-cast and heat treated conditions.
O-43: Microstructural Evolution during Deformation of 1 GPa Ultrahigh Strength-high Ductility Combination Austenitic Low Density Steel: Devesh Misra1; Jaehyun Kim1; L. Wei2; 1The University of Texas at El Paso; 2Shanghai Jiatong University
Low density steels are of significant interest because of light weight combined with high strength and ductility. We describe here the microstructural evolution during deformation of a low density steel characterized by tensile strength and elongation of 1125 MPa and 30.8%, respectively, via using post-mortem electron microscopy and electron back scattered diffraction of the deformed region. The plastic deformation was accommodated by pronounced planar dislocation slip and is attributed to the superposition of sheared ordered kappa precipitates and short-range ordering. Dynamic slip band refinement and shearing of precipitates led to constant strain hardening of the austenitic steel.
O-44: The Design Strategy and Creep Properties of Cr-free Model NiCo-based Superalloys: Victoria Tucker1; Sae Matsunaga1; Michael Titus1; 1Purdue University
Ni-based superalloys are used extensively in high temperature applications. With excellent creep and fatigue properties along with good corrosion resistance, Ni-based superalloys are an optimal design material for turbine blades and other high temperature, high strength applications. While superalloys have been used for decades, recent works have begun to reveal that, during deformation, solute segregation to planar defects are influenced by alloy compositions. In this work, our recent alloy design strategy via the CALPHAD method and experimental findings including creep results of γ’-containing Ni-30Co-Al-X-0.03Zr-0.5B (X=Ti,Ta,Nb) are presented. Based on these findings, we hypothesize that the presence of Co provides a driving force for segregation to planar defects. Furthermore, it has also been proposed that alloys whose compositions lie close to the γ+γ’/γ+γ’+η/δ phase boundary (low Al, high X alloys) would exhibit a propensity for segregation of η- and δ-formers to SISFs and SESFs.
O-45: The Validity of Using the Hollomon-Jaffe Parameter to Predict Hardness of Tempered Low-carbon High-performance Stainless-steel Alloys for Nuclear Applications: Shmuel Samuha1; Jeff Bickel2; Thomas Lienert3; James Valdez3; Tarasankar DebRoy4; Tuhin Mukherjee4; Stuart Maloy3; Peter Hosemann2; 1University of California, Berkeley Nuclear Engineering, and NRCN; 2University of California, Berkeley Nuclear Engineering; 3Los Alamos National Laboratory; 4The Pennsylvania State University
The Hollomon-Jaffe (H-J) parameter is traditionally employed to describe the combined effect of time and temperature in a tempering treatment, yet not to predict the hardness following a heat treatment (HT). The present work was undertaken with the object of exploring this last possibility. For this purpose, the low-carbon, high-performance Ferritic/Martensitic T-91 stainless-steel alloy, a potential candidate for structural steel in nuclear reactors, was chosen. The alloy was austenized at three different temperatures, yielding different onsets of prior austenite microstructures, then tempered using different soaking times and temperatures. In total, 51 HT combinations were evaluated. Variations in the hardness were interpreted in the context of fundamental metallurgical characteristics using advanced diffraction and analytical methods. Based on the H-J methodology, a logistic function was established, successfully predicting the decrease in hardness following tempering, estimating the onset of hardness changes and the end of the tempering.