Deformation Induced Microstructural Modification: Session IV: Deformation of Alloys I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Shaping and Forming Committee
Program Organizers: Arun Devaraj, Pacific Northwest National Laboratory; Suveen Mathaudhu, Colorado School of Mines; Kester Clarke, Los Alamos National Laboratory; Bharat Gwalani, North Carolina State Universtiy; Daniel Coughlin, United States Steel Corp

Tuesday 2:00 PM
March 16, 2021
Room: RM 38
Location: TMS2021 Virtual

Session Chair: Daniel Coughlin, Los Alamos National Laboratory


2:00 PM  Invited
Deformation Induced Precipitation (DIP) in Light Alloys: Theory and Experiments: Suhas Eswarappa Prameela1; Peng Yi1; Yannick Hollenweger2; Laszlo Kecskes1; Dennis Kochmann2; Michael Falk1; Timothy Weihs1; 1Johns Hopkins University; 2ETH Zurich
    Recent studies have shed new light onto the mechanisms that control deformation enabled precipitation in Aluminum and Magnesium Alloys. These studies show how defect structure, density, and distribution can be manipulated to obtain a high number density of nanoscale precipitates and fine solute clusters. However, many challenges remain with designing effective thermomechanical processing (TMP) routes. These include overcoming the competition between recrystallization and precipitation, decoupling the role of dislocations and vacancies in aiding the nucleation, and performing correlative microscopy studies. On the modeling side, there are challenges associated with capturing deformation gradients across multiple length scales and linking them to phase transformation processes. In this talk we will describe links between theory and experiments covering deformation enabled precipitation in Magnesium alloys and we will contrast them with those reported for Aluminum alloys.

2:30 PM  
Cyclic Deformation and Fatigue Behavior of 316L Stainless Steel Processed by Surface Mechanical Rolling Treatment: Luiz Carneiro1; Xiaogui Wang2; Yanyao Jiang1; 1University of Nevada, Reno; 2Zhejiang University of Technology
    The monotonic and cyclic behavior of 316L stainless steel (SS) with a gradient nanostructured (GNS) layer was investigated. The GNS layer was obtained using surface mechanical rolling treatment (SMRT). The plastic deformation levels achieved during the SMRT induced severe grain refinement, residual stresses, and martensitic phase transformation. The monotonic tensile strength of the SMRT 316L SS is increased by 13% and the elongation at failure is decreased by 25%, compared to the coarse-grained (CG) untreated specimen. Strain-controlled tension-compression fatigue tests were performed in both SMRT and CG specimens. The fatigue properties of the SMRT specimens are significantly enhanced, compared to the CG specimens. Furthermore, surface and subsurface fatigue crack initiation are observed, depending on the strain amplitude. The mechanisms involved in the enhancement of the fatigue properties due to the SMRT are discussed.

2:50 PM  
High Pressure Torsion Processed Maraging Steels: Microstructure and Mechanical Behaviour: Kevin Jacob1; Deepesh Yadav1; Saurabh Dixit2; Anton Hohenwarter3; Balila Jaya1; 1IIT Bombay; 2Mishra Dhatu Nigam Ltd.(Midhani); 3Montanuniversität Leoben
    Maraging steels are Fe-Ni martensitic steels with an unusual combination of strength and ductility. Strengthening results due to nano sized intermetallic precipitates that form in the highly dislocated matrix, on aging. High Pressure Torsion (HPT) has been utilised in this study to produce maraging steel 250 grade (AMS 6512) with finer lath spacing and a very high dislocation density, acting as nucleation sites for precipitation, and reverted austenite formation. Aging such a structure accelerates the precipitation kinetics substantially, whereas grain fragmentation and high dislocation density also leads to early onset of recrystallization all of which have subsequent bearing on the mechanical response of these maraging steels. HPT processed maraging steels show a 27% increase in strength while after aging, they show a 70% increase in strength corresponding to the non-HPT counterparts. Their ductility however shows a reverse trend, due to the change in morphology of the precipitates after HPT processing.

3:10 PM  Invited
Fabrication of Ultrafine Grained Ferritic Steels by Combining Dynamic Transformation and Dynamic Recrystallization: Nobuhiro Tsuji1; Lijia Zhao2; Nokeun Park3; Yanzhong Tian4; Akinobu Shibata5; 1Kyoto University; 2ArcelorMittal; 3Yeungnam University; 4Northeastern University; 5National Institute for Materials Science
    Ultrafine grained (UFG) steels having average grain sizes smaller than 1 micro-meter are known to show excellent mechanical properties. UFG microstructures in steels and other metallic materials can be realized by severe plastic deformation (SPD), but it is still difficult to apply SPD processed to large scale industries. On the other hand, we succeeded in making UFG ferritic microstructures in a 10Ni-0.1C steel by combining dynamic transformation (DT) from austenite to ferrite and dynamic recrystallization (DRX) of ferrite during thermo-mechanically controlled processing (TMCP) at elevated temperatures, Homogeneous ferrite microstructures with equaxed morphologies and sub-micrometer grain sizes could be obtained by the TMCP. The UFG specimen with the average grain size of 350 nm showed a yield strength of 953 MPa and total tensile elongation of 23%.

3:40 PM  Invited
Microstructural Evolution and Deformation Mechanisms in Segregation-Engineered Nanocrystalline Al Alloys: Glenn Balbus1; Johann Kappacher2; David Sprouster3; Jungho Shin4; Fulin Wang4; Jason Trelewicz3; Daniel Kiener2; Verena Maier-Kiener2; Daniel Gianola4; 1UCSB; 2Montanuniversität Leoben; 3Stony Brook University; 4University of California, Santa Barbara
    The nonequilibrium nature of amorphous solids such as metallic glasses (MGs) shares intriguing commonalities with grain boundaries in nanocrystalline (NC) materials, owing largely to the multiplicity of energy states inherent to disorder. These collective qualities underpin the attractive suite of properties in both material classes. MGs, in particular, offer vast tunability that can be accessed through nonequilibrium processing, but fall short in terms of temperature stability (structurally and mechanically). NCs alloys offer a potential marriage of these attributes: GBs with a spectrum of states, offering tunability through relaxation and rejuvenation processes, and interface-aware alloy design through segregation engineering, offering thermal stability via thermodynamic or kinetic means. We show experiments on NC Al alloys that exhibit tunability in the GB state and concomitant mechanical properties, and highlight an exemplary ternary alloy that exhibits a combination of high hardness at both room and elevated temperatures, homogeneous plasticity, and emergent thermal stability.

4:10 PM  
The Effect of Processing Parameters on the Microstructure and Performance of Ni-Mn-Ga Alloys: Pnina Ari-Gur1; Pranav Bhale1; Irek Musabirov2; Ronald Noebe 3; Vladimir Shavrov4; Victor Koledov4; 1Western Michigan University; 2Russian Academy of Sciences, Ufa; 3NASA Glenn Research Center; 4Russian Academy of Sciences, Moscow
    Ni-Mn-based Heusler alloys demonstrate outstanding functional properties, such as giant magnetocaloric effect and magnetic shape-memory. Larger magnetocaloric effect is achieved when the temperature of the magnetic and crystallographic phase transitions merge. For applications at the micro- and nano-scale, such as MEMS and NEMS, special processing is needed. The nature of the process and its parameters, greatly affect the microstructure and the resulting properties and performance. In the current work, Ni-Mn-Ga based alloys were manufactured by three methods – one was melt-spinning and two processes of severe plastic deformation (SPD). One SPD process was high-pressure torsion (HPT) and the other, multiple isothermal forming (MIF). The effects of process parameters, such as the number of torsion passes for the SPD and cooling rates for the melt-spun samples, on the resulting microstructure, magnetic nature, crystallographic structures, temperature and nature of their phase transformations, crystallographic texture, and internal stresses were studied and conclusions drawn.

4:30 PM  
Thermomechanical Processing of Dilute Mg-Zn-Ca Alloys: Jenna Krynicki1; Laszlo Kecskes1; John Gibbins1; Zhigang Xu2; Timothy Weihs1; 1Johns Hopkins University; 2North Carolina A&T State University
    The use of lightweight metals in structural applications has sparked renewed interest in Mg alloys, as they can offer high specific strengths. Under extreme, high-rate loading conditions, spall strength and dynamic strength determine functionality. In such applications, attempts to strengthen Mg alloys with precipitates may prove inadequate as second phase particles can act as void nucleation sites that lower spall strength. Therefore, we focus on grain refinement with a minimal number of precipitates, using a Mg-1Zn-0.2Ca (wt%) alloy as an alternative to precipitation strengthening. The alloy was processed via Equal Channel Angular Extrusion (ECAE), implementing multiple extrusion routes. We report the resulting microstructures as a function of route and number of passes, identifying the degree of recrystallization, grain refinement, and texture. We also describe the mechanical properties of the fully processed samples using small-scale, quasi-static tension tests, exploring improvements in strength and ductility.