Mechanical Behavior at the Nanoscale V: Deformation and Failure
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Mechanical Behavior of Materials Committee, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Christopher Weinberger, Colorado State University; Megan Cordill, Erich Schmid Institute of Materials Science; Garritt Tucker, Colorado School of Mines; Wendy Gu, Stanford University; Scott Mao; Yu Zou, University of Toronto
Thursday 2:00 PM
February 27, 2020
Room: Santa Rosa
Location: Marriott Marquis Hotel
Session Chair: Jiangwei Wang, Zhejiang University; Wendy Gu, Stanford University
2:00 PM Invited
Interface-dominated Plasticity in Metallic Nanostructured Materials: Jiangwei Wang1; Qi Zhu1; Siyuan Wei1; Chuang Deng2; Scott X. Mao3; Frederic Sansoz4; 1Zhejiang University; 2The University of Manitoba; 3University of Pittsburgh; 4The University of Vermont
Interfaces, including grain boundaries (GB s), twin boundaries (TBs) and interphase boundaries, critically influence the mechanical properties and deformation mechanisms in metals and alloys. In this talk, I will present our recent progresses on the atomistic mechanisms governing the interface-dominated plasticity in metallic nanostructured materials, using the in situ nanomechanical testing. We revealed that the grain boundaries can migrate reversibly in shear loading cycles through a disconnection-mediated mechanism, in which the nucleation, lateral propagation and dynamic interactions of different types of GB disconnections control the deformation; the dislocation-twin interactions in nanotwinned metallic materials are strongly influenced by the twin size, where the dislocation slip on the uncommon (001) planes can be effectively activated with the twin size decreases；while in metallic nanolamellar materials, the interface structures strongly influence the deformation and crack formation. These findings provide novel insights into the interface-dominated plasticity in a broad class of metallic materials.
2:40 PM
The Influence of 3D Interfaces on the Mechanical Behavior of Nanoscale Metallic Multilayers: Justin Cheng1; Kevin Baldwin2; Youxing Chen3; Nan Li2; Irene Beyerlein4; Nathan Mara1; 1University of Minnesota, Twin Cities; 2Los Alamos National Laboratory; 3University of North Carolina, Charlotte; 4University of California, Santa Barbara
Nanoscale metallic multilayers (NMMs) are layered composites that are ideal for exploring the role of interfacial structure on deformation behavior. Most NMMs studied so far have been synthesized with atomically sharp, or 2D interfaces. In contrast, this work focuses on interfaces that are structurally graded in the out-of-interface plane direction. These “3D interfaces” influence the hardness and deformability of materials in ways that are not yet well quantified. We show that 3D interface-containing Cu/Nb NMMs display distinct anisotropy in mechanical response at single-phase layer thicknesses of <20 nm. TEM characterization of the atomic structure of 3D interfaces before and after deformation reveal the underpinnings of anisotropy and size effects found in nanoindentation and in-situ micropillar compression of NMMs. These effects can be quantified and explained by the relationship between the dominant deformation mechanisms (dislocation-interface interactions, interfacial sliding) and the atomic structure of 3D interfaces of varying thickness.
3:00 PM
Nanomechanical Studies of Dual-phase Titanium Alloys Made by Additive Manufacturing: Zhiying Liu1; Yu Zou1; 1University of Toronto
The mechanical properties of a laser melting deposited (LMD) Ti–6Al–2Zr–Mo–V alloy are investigated using the nanoindentation and micro-cantilever bending methods. The results show that hardness and reduced modulus of individual phases made by additive manufacturing are comparable with those made by conventional casting or forging methods. The mechanical difference between α and β phases associated with the crack path will be discussedThis work highlights the comparison of properties of individual phases made by various manufacturing methods and elucidates the relationship between mechanical contrast between phases and corresponded crack propagation mechanisms.
3:20 PM
Cu-graphene Multilayer Composite for Robust Electronic Interconnect Material: Wonsik Kim1; Sang-Min Kim2; Byungil Hwang3; Seung Min Han1; 1Korea Advanced Institute of Science and Technology; 2Korea Institute of Machinery and Materials; 3Chung-Ang University
Cu-graphene multilayer composite, as an interconnect material, is a very promising material system. Metal-graphene nanolayered composite is known to have ultra-high strength as the graphene hinders dislocation movements across its interface. The same graphene can be an effective interface for deflecting fatigue cracks that are generated under cyclic bending. In this work, Cu-graphene composites were tested for bending fatigue, which have shown 5 times enhancement in fatigue resistance compared to conventional Cu thin film. Fatigue cracks that are generated within the Cu layer were observed by the cross-sectional SEM and TEM to be stopped by the graphene interface. In MD simulation, Cu-graphene showed limited accumulation of dislocations at the film/substrate interface. In addition, more efficient fabrication process of Cu-graphene composite, by dry transfer of graphene and electrodeposition of Cu, is proposed. Nano-pillar indentation are performed and compared with previous studies to confirm that this Cu-graphene composite display similar strengthening effect.
3:40 PM Break
4:00 PM
Investigation of Crack Nucleation and Propagation During Nanoindentation of Silicate Glasses: Yvonne Dieudonne1; George Pharr1; 1Texas A&M University
Different aspects of cracking behavior have been studied using nanoindentation with triangular pyramidal indenters with centerline-to-face angles in the range of cube corner (35.3°) to Berkovich (65.3°). Two different glass structures have been analyzed and compared; anomalous glass (fused quartz) and normal glass (soda lime silicate), which deform primarily by densification and shearing processes, respectively. Those different deformation processes are anticipated to lead to different stress fields around the contact area resulting in different cracking morphologies. Nanoindentation at various loads (e.g., 3 mN -1000 mN) helped to identify a load dependency of the cracking behavior. Surface cracking was documented using atomic force microscopy and scanning electron microscopy. Results show that cracking is enhanced by sharper indenters and higher loads. However, there exists a distinct crack initiation threshold, below which no crack formation can be observed, which is dependent on the glass system as well as the indenter geometry.
4:20 PM
Comparison of Intergranular Fracture Behavior Between Sulfur Doped Nickel Grain Boundaries: Doruk Aksoy1; Rémi Dingreville2; Douglas E. Spearot1; 1University of Florida; 2Sandia National Laboratories
The fracture behavior of crystalline metals is affected by the presence of segregants in the system. One system which displays this behavioral change is the nickel-sulfur system. The embrittling behavior caused by sulfur is quantified by using a thermodynamic property known as the embrittling potency. This property can be used to characterize the intrinsically ductile nickel grain boundaries by their susceptibility to embrittlement. In this work, an extensive study of pure tilt grain boundaries is conducted via molecular dynamics simulations to explore the relationship between sulfur segregation and intergranular fracture behavior from a structural point of view. The embrittling potencies across lattices are matched mechanically to isolate the role of the grain boundary structure on interfacial fracture. Then, using cohesive-zone volume elements, the decohesion behavior for different grain boundaries is extracted. This data is analyzed to categorize and characterize grain boundaries in terms of their structural and fracture related properties.