Strength prediction in NiCo alloys – The role of composition and nanotwins

Chowdhury, Piyas; Şehitoğlu, Hüseyin; Maier, Hans Jürgen; Rateick, Richard G.

doi:10.1016/j.ijplas.2015.07.002

Cited by 54 publications

(8 citation statements)

References 80 publications

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“…For example, recent advances note that the parameter

γ_{us}

subjected to alloying and/or an increased presence of interfaces could be extracted precisely using combined MD and quantum mechanical simulations (e.g. density functional theory) . Mesoscale normalizations could be applied to convert

γ_{us}

into corresponding frictional stresses to be used in continuum formulations.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

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Mechanisms of fatigue crack growth – a critical digest of theoretical developments

Chowdhury

Şehitoğlu

2016

Fatigue Fract Eng Mat Struct

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128

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A B S T R A C T Recent advances in the processing technology are permitting the manufacture of novel metallic materials with superior fatigue properties via microstructure tailoring. In the light of these promising developments, there is a rising need for establishing a synergy between state-of-the-art experimental characterizations and physically based theoretical underpinnings. A revisit to the existing predictive literature is thus a timely requirement prior to furthering new design guidelines against cyclic damage. To that end, this paper recounts an overview of the key mechanistic and analytical theories on the fatigue crack growth mechanisms. Emphasis is placed on categorizing the proposed modelling endeavours based on their fundamental principles. In doing so, contributions and limitations thereof are carefully examined on the basis of most updated experimental revelations. The objective is to provide a perspective to the current generation of engineers and researchers alike. This concise yet critical narrative would essentially assist in formulating even more advanced microstructure-damage relationships in the modern context. A commentary is added at the end outlining the promising avenues for future research.CTOD, FCG = crack tip opening displacement, fatigue crack growth MD, DFT = molecular dynamics, density functional theory RVE = representative volume element LEFM, EPFM = linear elastic and elastic plastic fracture mechanics E, H = Young's modulus, plastic modulus GB = grain boundary K max , K min , K open , = maximum, minimum and opening stress-intensity factors K c = fracture toughness under mode I loading ΔK eff th , ΔK th = (effective) threshold stress intensity factor range da/dN = fatigue crack growth rate per cycle (a is the crack length and N is the number of cycles) L deflect , θ deflect = length and angle of a deflected crack respectively θ = angle between slip and crack paths σ yield , σ cyclic yield , σ fracture = monotonic, cyclic yields strengths and static fracture strength σ ′ f , ε ′ f = strength and ductility coefficient in Coffin-Manson-Basquin rule: Δε plastic ¼ 2ε ′ f 2N f ð Þ c σ eff , σ hydro = effective and hydrostatic stress ρ * = effective radius of a sharp crack ρ slip , _ ρ vacancy , ρ interface = dislocation density, vacancy generation rate and interface density P H 2 , P O 2 = partial pressures of hydrogen and oxygen m, C = Paris exponent, Paris proportionality constant m Schmid = Schmid factor τ friction , τ forward friction , τ reverse friction = friction (Peierls) stress for free (unobstructed), forward and reverse dislocation glide

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“…For example, recent advances note that the parameter

γ_{us}

γ_{us}

into corresponding frictional stresses to be used in continuum formulations.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…a cross‐slip situation). Between these two extremities, there are myriad other possibilities of reaction outcomes . Essentially, each reaction would be unique in terms of the degree of the resistance to the oncoming slip; and hence, the attendant crack behaviours in the long run.…”

Section: Dislocation Blockage Modelsmentioning

confidence: 99%

Mechanisms of fatigue crack growth – a critical digest of theoretical developments

Chowdhury

Şehitoğlu

2016

Fatigue Fract Eng Mat Struct

Self Cite

128

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“…For example, a very low energy barrier to create the corresponding shear displacement would make slip nucleation spontaneous. The exact topography of the Peierls energy surface depends on: (a) the crystal lattice structure and (b) effects of alloying [37,44,45].…”

Section: Importance Of Capturing Atomistic Energeticsmentioning

confidence: 99%

A revisit to atomistic rationale for slip in shape memory alloys

Chowdhury

Şehitoğlu

2017

Progress in Materials Science

113

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Performance degradation in shape memory alloys (SMA) arises due to a gradual loss of strain recoverability attributable to slip mediated plasticity. The slip-induced changes in SMAs can be profound creating accumulation of permanent strains, altering the critical stress and hysteresis in an adverse manner. Slip nucleation in ordered SMA lattices can often be triggered due to energetically favorable dissociation reactions. Partial slip can dominate over full slip, generating planar defects (e.g. anti-phase boundary, superlattice or complex stacking faults) as evidenced through electron microscopy. Considerable advances are made lately on physically rationalizing the observed plastic micromechanism(s) benefitting from quantum mechanical models. In-depth analyses of crystal variables (e.g. lattice ordering, atomic stacking and stable/metastable fault structures) subjected to intrinsic solid-state effects have unequivocally established the genesis of empirical slipping propensity in terms of atomic fault energetics. This article systematically revisits the empirical physical evidence of slip in important SMAs from the literature, presents the pertinent experimental findings, and then embarks on reviewing the

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“…Nanocrystalline metals have been the subject of numerous studies because of their potential use in high strength applications (Chowdhury et al, 2015;Chowdhury et al, 2016;Min et al, 2014;Salehinia et al, 2014;Yuan et al, 2016). The large densities of grain boundaries in these materials dramatically change the deformation behavior from that observed in their conventional polycrystalline counterparts (Burbery et al, 2015;Hahn and Meyers, 2015;Ivanisenko et al, 2016;Khalajhedayati et al, 2016;Upadhyay et al, 2016;Zhang et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Effects of solutes on dislocation nucleation from grain boundaries

Borovikov

Mendelev

King

2017

International Journal of Plasticity

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When grain sizes are reduced to the nanoscale, grain boundaries (GB) become the dominant sources of the dislocations that enable plastic deformation. We present the first molecular dynamics (MD) study of the effect of substitutional solutes on the dislocation nucleation process from GBs during uniaxial tensile deformation. A simple bi-crystal geometry is utilized in which the nucleation and propagation of dislocations away from a GB is the only active mechanism of plastic deformation. Solutes with atomic radii both larger and smaller than the solvent atomic radius were considered. Although the segregation sites are different for the two cases, both produce increases in the stress required to nucleate a dislocation. MD simulations at room temperature revealed that this increase in the nucleation stress is associated with changes of the GB structure at the emission site caused by dislocation emission, leading to increases in the heats of segregation of the solute atoms, which cannot diffuse to lower-energy sites on the timescale of the nucleation event. These results contribute directly to understanding the strength of nanocrystalline materials, and suggest suitable directions for nanocrystalline alloy design leading toward structural applications.

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Strength prediction in NiCo alloys – The role of composition and nanotwins

Cited by 54 publications

References 80 publications

Mechanisms of fatigue crack growth – a critical digest of theoretical developments

Mechanisms of fatigue crack growth – a critical digest of theoretical developments

A revisit to atomistic rationale for slip in shape memory alloys

Effects of solutes on dislocation nucleation from grain boundaries

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