Deformation-induced Manipulation of Defect Structures and Hierarchical Microstructures: Session I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Bharat Gwalani, North Carolina State Universtiy; Kester Clarke, Los Alamos National Laboratory; Eric Lass, University of Tennessee-Knoxville; Vahid Tari, ATI - Allegheny Technologies Incorporated
Wednesday 8:30 AM
March 22, 2023
Room: Sapphire P
Location: Hilton
Session Chair: Bharat Gwalani, North Carolina State University; Vahid Tari, Allegheny Technologies Incorporated
8:30 AM Invited
Processing Heterostructures Using Deformation Techniques: Yuntian Zhu1; 1City University of Hong Kong
Heterostructured materials consist of heterogeneous zones with dramatic (>100%) variations in mechanical and/or physical properties. The interaction in these hetero-zones produces a synergistic effect where the integrated property exceeds the prediction by the rule-of-mixtures. Heterostructures are found to have the capability to produce unprecedented strength and ductility that are considered impossible from our textbook knowledge and materials history. Importantly, HS materials can be produced by current industrial facilities at large scale and low cost. In this talk I’ll present an overview on the processing of various heterostructures and their effectiveness in improving mechanical properties.
8:55 AM Invited
Nanostructural Hierarchy in Metallic Materials for Extended High Temperature Stability: Subhashish Meher1; Sourabh Kadambi1; Thomas Lillo1; 1Idaho National Laboratory
The structural hierarchy exhibited by materials on more than one length scale can play a major part in determining bulk material properties. Understanding the hierarchical structure can lead to new materials with physical properties tailored for specific applications. A combined experimental and phase-field modeling approach has been used to explore such hierarchical structures at nanoscale for enhanced coarsening resistance in a gamma-gamma prime Ni-base superalloy and a BCC-B2 based high entropy alloy (HEA). Experiments and phase-field modeling highlight the importance of embedded phases (gamma and BCC respectively) to promote stability of (gamma-prime and B2 respectively) and to delay coarsening of the encompassing precipitates. Phase field modeling based on experimental results reveals the reasoning for enhanced precipitate coalescence in these alloys. This research on hierarchical structures establishes a new paradigm for alloy design for specific needs of emerging nuclear, fossil and solar energy applications.
9:15 AM
Exploiting Hydrogen Segregation Effects for Controlling Microstructure Evolution: Haoxue Yan1; C. Cem Tasan1; 1Massachusetts Institute of Technology
Even ppm levels of hydrogen in metals can change behaviors of crystallographic defects, such as dislocations and grain boundaries. Here, we propose that such effects of hydrogen can be used to regulate microstructure evolution. In this presentation, we show that a gradient microstructure can be achieved in commercially pure aluminum by introducing hydrogen during recrystallization treatments. To understand the fundamental aspects of this approach, we study the relationship between recrystallization driving force and hydrogen content. The effect of hydrogen on recrystallization kinetics are also examined via scanning differential calorimetry analyses and discussed in terms of Turnbull’s classical rate equation for interface migration. The applicability of the proposed approach in other metal systems will be discussed. This work suggests new strategies to overturn the detrimental effects of hydrogen into opportunities for designing beneficial microstructures.
9:35 AM
Microstructural Inelastic Deformation and Fracture Modes in Crystalline Materials: M. Chen1; Dongyue Xie,2; N. Li2; Mohammed Zikry1; 1North Carolina State University; 2Los Alamos National Laboratory
Interrelated aspects of thermo-mechanical behavior with a specific focus on microstructural characteristics, such as partial and total dislocations densities and grain-boundary (GB) that span the nano to the micro, and how these characteristics affect failure modes, such as fracture nucleation in crystalline materials, will be presented. Recently developed methodologies have been used for a detailed analysis of fracture nucleation and the accurate characterization of intergranular and transgranular crack growth. Criteria for dislocation-density mechanisms and immobilization are directly related to interactions with GB ledges and propagating cracks in polycrystalline aggregates. The effects of interfaces, such as GB blockage, dislocation-density motion, and pileups on fracture nucleation will be discussed. The predictions are validated with micropillar compression experiments to provide further understanding of how defects, such as partial and total dislocation-densities, affect failure nucleation and intergranular and transgranular fracture.
9:55 AM Invited
Under Pressure - Exploring the Synergy of High Pressure Deformation Mechanisms of Metals and Rocks: Suveen Mathaudhu1; 1Colorado School of Mines
For decades, severe plastic deformation approaches such as high pressure torsion and equal channel angular extrusion have probed the limits of novel defect and microstructure evolution under pressure-confined shear deformation. However, deformation under similar conditions has been occurring for eons in the geological materials in earth's lithosphere. Cross-cutting theories on the nature of intense pressure and shear-driven structural evolution in metals and geological materials will be presented, along with novel characterization methods used to understand defect evolution for the corresponding conditions and time-scales. The discussion will forecast the ability to use laboratory-scale tools and simulant materials to extend our understanding of how the world has moved underneath us and how it may deform in other parts of the universe.
10:15 AM Break
10:35 AM Invited
Phase Stability in Alloys during Severe Plastic Deformation in the High Strain Limit: Pascal Bellon1; Robert Averback1; Yinon Ashkhenazy2; 1University of Illinois at Urbana-Champaign; 2Hebrew University of Jerusalem
Mechanical alloying has become a valuable processing scheme, much studied since the seminal work of JS Benjamin over 50 years ago. Yet, no general model describes how alloy phases evolve during severe plastic deformation, whether unique steady states stabilize at high strain, and if so whether it is independent of the initial state of the system. An attractive model for describing such a driven alloy system is the effective temperature model proposed by Martin as it builds an effective potential that acts like a free energy in system driven from equilibrium. In this presentation we use computer simulation and SPD experiments on model alloys to highlight the successes and weakness of this model. We focus particular attention on the use of ternary additions to systematically vary alloy properties such as heat of mixing, shear modulus, and interphase energies.
11:00 AM Invited
Universal Trend in the Non-Equilibrium Evolution of Metastable Grain Boundaries at Extreme Conditions: Yue Fan1; 1University of Michigan
In ultrafine-grained materials and under non-equilibrium processing conditions, GBs are rarely in ground states and would instead present a multiplicity of microscopic metastable states, endowing the system with enhanced tunability. For example, recent experiments show nanocrystals can be rejuvenated by femtosecond laser and their hardness can be effectively controlled. However, a mechanistic understanding on metastable GBs’ evolution remains unclear. Here we investigate a variety of metastable GBs under fast driving conditions using atomistic simulations. Assisted with data-mining algorithm to analyze the annealing behavior of GBs at various conditions, we construct a high-fidelity energetic evolution map, showing that it can be divided into an ageing regime and a rejuvenating regime over the energy—temperature space. The ageing/rejuvenating stems from the energy imbalance during the interchanges between metastable states, and a kinetic equation is subsequently derived. The predicted energetic evolution and its implication on metastable GBs’ mechanical performance are consistent with experiments.
11:20 AM
Role of Cold Sprayed Microstructure on Tensile and Fatigue Behavior for AA7075: Christopher Williamson1; Ning Zhu1; Arthur Webb1; Brian Jordon2; Luke Brewer1; 1University of Alabama; 2Baylor University
This paper will compare and contrast the microstructure-property relationships for cold sprayed and wrought (T6) AA7075 material. Cold spray deposition is a solid state, powder-based additive processing approach that uses supersonic particle impingement to build up the material into complex geometries. The cold sprayed microstructure is fundamentally bimodal in grain size and has an inhomogeneous nanophase distribution. Cold sprayed materials were produced using three different feedstock powders with intentional differences in the precipitate distribution: as-atomized, solutionized, and overaged. After deposition, the tensile behavior between these three materials is markedly different with as-atomized material being the strongest but least ductile, while overaged material is the weakest but most ductile. The stress-cycle fatigue behavior of these materials shows that is it not the strength of the material that controls their life, but instead our data strongly suggests that it is the role of intermetallic networks that is central to fatigue performance.
11:40 AM
Self-lubricating Ni-based Superalloy Composites Processed by Severe Plastic Deformation: Manoel Kasalo1; Sebastian Suarez2; Andrea Bachmaier1; 1Erich Schmid Institute of Materials Science of the Austrian Academy of Sciences; 2Department of Materials Science, Campus D3.3, 66123 Saarbrücken, Germany
Low friction and high wear resistance can result in a prolonged operating lifespan of mechanically stressed components. Both characteristics could be achieved in nanostructured self-lubricating metal matrix composites, by adjusting the matrix microstructure and the lubricant integration to it. In this work, high-pressure torsion (a severe plastic deformation technique) was used to incorporate solid lubricants (e.g., Graphite, MoS2) in different quantities into Ni-based superalloys. The aim is to determine which amount of solid lubricant and which deformation parameters ensure an improvement of the tribological performance, without compromising the mechanical properties of the composites. A better distribution of the solid lubricant phase was observed by scanning electron microscopy when the powders were colloidally mixed before the deformation process. Mechanical properties were evaluated by micro tensile tests and microhardness measurements, observing increased values in the latter. The self-lubricity of the composites was investigated by using a ball-on-flat tribometer.
12:00 PM Invited
The Role of Deformation Induced Defects on Phase Evolution in High Entropy Alloys: Abhishek Sharma1; Sriswaroop Dasari1; Bharat Gwalani1; Mohan Sai Kiran Nartu1; Yao-Jen Chang2; Stephane Gorsse3; An-Chou Yeh2; Rajarshi Banerjee1; 1University of North Texas; 2National Tsing Hua University; 3University of Bordeaux
Though a fine scale second phase distribution is a potent strengthening mechanism for alloys, achieving high precipitate density is often difficult owing to sluggish precipitation kinetics and limited heterogeneous nucleation sites. More specifically in case of transition element based complex concentrated alloys (CCAs) or High Entropy Alloys (HEAs), precipitation of equilibrium phases, e.g., ordered B2 or sigma phase, can be limited due to their high nucleation barrier for homogeneous precipitation within the face-centered cubic (FCC) matrix. This can lead to the competing homogeneous nucleation of a metastable ordered L12 phase which has a substantially lower nucleation barrier. Using different CCAs/HEAs as examples, deformation processing has been employed to introduce a large number density of homogeneously distributed heterogeneous nucleation sites within the FCC matrix, to manipulate the phase fraction, morphology, and distribution of the equilibrium precipitates. This approach of tailoring microstructure is widely applicable to other multi-component alloys including RHEAs.