The effects of microstructure and microtexture generated during solidification on deformation micromechanism in IN713C nickel-based superalloy

Liu, Gang; Cantó, Jorge; Winwood, S.; Rhodes, Katie; Birosca, S.

doi:10.1016/j.actamat.2018.01.062

Cited by 64 publications

(15 citation statements)

References 36 publications

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“…The GND and slip trace mapping were calculated using in-house python code. The principles and details of the calculations were reported previously in (Liu et al, 2018;Birosca et al, 2014Birosca et al, , 2019. Furthermore, specific site extraction close to initiation sites and beneath fatigue striations for the dislocation analyses were prepared using Focus Ion Beam (FIB) and characterised by means of FEI-Talos 200F utilising Scanning Transmission Electron Microscopy (STEM)-High Angle Annular Dark field (HAADF).…”

Section: Microstructure and Microtexture Characterisationsmentioning

confidence: 99%

“…Moreover, superalloy produced via investment casting also has the advantage of minimising machining process compared to the forged alloys, which is of significant economic efficiency and enable massive industrial production. IN713C has been widely used as turbocharger turbine wheel materials in the automotive industry for decades (Salvat Cantó et al, 2018;Liu et al, 2018). However, casting has an inherent problem of porosity formation (shrinkage and/or gas pore) and usually results in relatively large grains, which degrades the alloy's fatigue property to a great degree.…”

Section: Introductionmentioning

confidence: 99%

“…They demonstrated that the HCF life might be affected by average secondary dendrite arm spacing in addition to the drastic difference in nucleation site size and average grain size. In our earlier work (Liu et al, 2018) we proposed a strain accommodation model via lattice rotation of interdendritic area in the late stage of crack propagation in IN713C superalloy. However, the question of to what extend the dendritic structure affects crack propagation and overall deformation mechanism remained unanswered.…”

Section: Introductionmentioning

confidence: 99%

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The effects of grain size, dendritic structure and crystallographic orientation on fatigue crack propagation in IN713C nickel-based superalloy

Liu

Winwood

Rhodes

et al. 2020

International Journal of Plasticity

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The polycrystalline IN713C produced via investment casting is one of the widely-used nickel-based superalloy in automotive and aerospace industries. This alloy, however, has an apparent inhomogeneous microstructure generated during casting and contains dendritic structure that gives rise to strain localisation during loading. Yet, the effect of dendritic structure, grain size and shape as well as crystallographic orientation, which directly influence fatigue property and deformation micromechanism in the components, is rarely studied. In the present study, IN713C cast bars are tailored with three different grain structures, i.e., transition, equiaxed and columnar, with substantial grain size variations. The produced bars were tested under strain controlled LCF (Low Cycle Fatigue) and stress controlled HCF (High Cycle Fatigue) conditions at 650 °C. The results showed that most of fatigue cracks initiated from casting pores and fatigue life extended in the microstructure with a small grain size during both HCF and LCF loadings. It is also demonstrated that fatigue striations were mainly observed within dendritic areas during crack propagation, whereas the higher GND (Geometrically Necessary Dislocation) density were predominantly observed in the interdendritic 2 areas. Here, we propose a concept of 'Crack Propagation Unit (CPU)' for better description of deformation mechanism at local scale during fatigue loading by combining fracture surface characteristic methodology and dislocation distribution analyses within the dendritic structural unit. Furthermore, this model to understand the deformation micromechanism can provide a new perspective on the interpretation of Hall-Petch relationship in casting materials that contain dendritic structure. This is further demonstrated via direct correlation of the high crack propagation resistance with the crack path divergence instead of the dislocation pileup at the grain boundary or in-between the γ/ γ' channels. Moreover, by utilising serial sectioning method followed by layered EBSD scanning, quasi-3-D grain orientation mappings were obtained, and crystallographic texture information were directly correlated with the fracture surface observations. This allowed an investigation of the influence of orientation of individual grains and micro/macro texture on crack propagation rate. The critical stage of crack propagation in fatigue life and its correlations with microstructural features is established, offering potential practical applications by controlling the investment casting process parameters.

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Section: Microstructure and Microtexture Characterisationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The effects of grain size, dendritic structure and crystallographic orientation on fatigue crack propagation in IN713C nickel-based superalloy

Liu

Winwood

Rhodes

et al. 2020

International Journal of Plasticity

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“…The GND and Slip Trace maps were generated from EBSD data using in-house code. The principle of GND and Slip Trace maps are calculations is reported in Birosca et al, 2014, Liu et al, 2018 The orientation data was collected using 100 nm step size in order to determine the orientation spread within individual grains at relatively small length scales. The diffraction pattern binning of 4 x 4 was employed and the noise floor was calculated using the method described in Jiang et al, 2013 and it is found to be much less that average GND values.…”

Section: Scanning Electron Microscopy (Sem) and Electron Backscatter mentioning

confidence: 99%

The dislocation behaviour and GND development in a nickel based superalloy during creep

Birosca

Liu

Ding

et al. 2019

International Journal of Plasticity

133

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In the current study, dislocation activity and storage during creep deformation in a nickel based superalloy (Waspaloy) was investigated, focussing on the storage of geometrically necessary (GND) and statistically stored (SSD) dislocations. Two methods of GND density calculations were used, namely; EBSD Hough Transformation and HR-EBSD Cross Correlation based methods. The storage of dislocations, including SSDs, was investigated by means of TEM imaging. Here, the concept of GND accumulation in soft and hard grains and the effect of neighbouring grain orientation on total dislocation density was examined. Furthermore, the influence of applied stress (below and above Waspaloy yield stress) during creep on deformation micro-mechanism and dislocation density was studied. It was demonstrated that soft grains provided pure shear conditions at least on two octahedral (111) slips for easy dislocation movement reaching the grain boundary without significant geometrically necessary accumulation in the centre of the grain. Hence, the majority of the soft grains appeared to have minimum GND density in the centre of the grain with high GND accumulation in the vicinity of the grain boundaries. However, the values and width of accumulated GND depended on the surrounding grain orientations. Furthermore, it was shown that the hard grains were not favourably oriented for octahedral slip system activation leading to a grain rotation in order to activate any of the available slip systems. Eventually, (i) the hard grain resistance to deformation and (ii) neighbouring grain resistance for the hard grain reorientation caused high GND density on a number of octahedral (111) slip systems. The results also showed that during creep below the yield stress of Waspaloy (500 MPa/700C), the GND accumulation was relatively low due to insufficient microscopic stress level. However, the regions near grain boundaries showed high GND density.Whereas, in addition to the movement of pre-existing dislocations (SSD and GND) at higher mobility rate under 800 MPa/700C above yield creep condition, large numbers of dislocations were generated and moved toward the grain boundaries. This resulted in much higher GND density but narrower width of high intensity GND near the grain boundaries. It is concluded that although GND measurement by means of EBSD can provide a great insight of dislocation accumulation and its behaviour, it is critical however to consider SSD type which is also contributes to the strain hardening of the materials.

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“…This is consistent with the previous study on RR1000 during thermomechanical fatigue testing. [21][22][23] As postulated in Reference 21 and demonstrated and validated here, the octahedral slip system in the soft grain can be easily activated (high SF) and this can facilitate uniform pure shear condition and an easy yield for the soft grains without the need for grain reorientation. Moreover, the pure shear condition in soft grains allows unrestricted movement of dislocations on (111) slips.…”

Section: Soran Biroscamentioning

confidence: 82%

Crystallographic Orientation Relationship with Geometrically Necessary Dislocation Accumulation During High-Temperature Deformation in RR1000 Nickel-Based Superalloy

Birosca

2018

Metall Mater Trans A

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In the current study, it is demonstrated that soft grains along 〈100〉 fiber provided a pure shear condition for easy dislocation movement leading to a relatively low dislocation density. The hard grains along the 〈111〉 fiber, however, were not favorably oriented for slip system activation and caused high dislocation accumulation. It is concluded that the average overall dislocation density does not provide a meaningful value, as it is largely dependent on the original material crystallographic texture, the numbers of hard and soft grains in the electron backscatter diffraction (EBSD) mapped area, and the grain size factor.

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The effects of microstructure and microtexture generated during solidification on deformation micromechanism in IN713C nickel-based superalloy

Abstract: The effects of microstructure and microtexture generated during solidification on deformation micromechanism in IN713C nickel-based superalloy. Acta Materialia http://dx.

Cited by 64 publications

References 36 publications

The effects of grain size, dendritic structure and crystallographic orientation on fatigue crack propagation in IN713C nickel-based superalloy

The effects of grain size, dendritic structure and crystallographic orientation on fatigue crack propagation in IN713C nickel-based superalloy

The dislocation behaviour and GND development in a nickel based superalloy during creep

Crystallographic Orientation Relationship with Geometrically Necessary Dislocation Accumulation During High-Temperature Deformation in RR1000 Nickel-Based Superalloy

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