Micro-mechanism of the effect of grain size and temperature on the mechanical properties of polycrystalline TiAl

Ding, Jing; Tian, Yu; Lu-sheng, Wang; Huang, Xia; Zheng, Haoran; Song, Kun; Zeng, Xiangguo

doi:10.1016/j.commatsci.2018.10.019

Cited by 32 publications

(6 citation statements)

References 43 publications

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“…Nevertheless, as the dislocation density saturates, the dislocation motions are blocked and part of SFs disappears (Figure 6j–l). This is why the stress–strain curves of samples with larger grain sizes produced sawtooth fluctuations [ 40 ] (described in Figure 2b–d). Figure 6j–l and m–o shows that GB activities occur during the plastic deformation of both structures.…”

Section: Resultsmentioning

confidence: 99%

Grain Distribution for Optimal Strength in Homogeneous and Gradient Nano‐Grained Coppers

Qiang

Long

2023

Adv Eng Mater

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The distribution of grains plays a crucial role in determining the strength of polycrystalline copper when the grain size is constant. Herein, the mechanical properties of homogeneous nano‐grained (HNG) and gradient nano‐grained (GNG) coppers with different grain distributions are examined using molecular dynamics (MD) simulations. The HNG‐ordered structure has all triple junctions (TJs), whereas the random structure contains many quadruple and quintuple junctions. When grain size is below the critical size in the inverse Hall–Petch relationship, the high‐density TJs in the HNG‐ordered structure effectively inhibit grain boundary (GB) softening compared with the random structure, leading to higher strength. However, when grain size is above the critical size, subgrains are produced inside the large grains due to dislocation slip. In addition, disordered atoms in HNG‐random structure are stacked in the quadruple and quintuple junctions, resulting in thicker GBs. This triggers grain boundary migration, and forms more subgrains at GBs. Subsequently, grain boundary sliding and grain rotation of subgrains induce partial recrystallization in the structure. This consecutively triggered deformation mechanism leads to extra strengthening in the random structure. Further research indicates that combining small‐grained ordered and large‐grained random structures can be a new approach to effectively strengthen GNG materials.

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Section: Resultsmentioning

confidence: 99%

Grain Distribution for Optimal Strength in Homogeneous and Gradient Nano‐Grained Coppers

Qiang

Long

2023

Adv Eng Mater

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“…For traditional nanograined refractory alloys, the MD simulations also show the inverse Hell–Petch relationship when the average grain size is smaller than the critical size. For example, the binary NiCo [ 27 ] and TiAl [ 33 ] refractory alloys show the inverse Hell–Petch relationship when the grain sizes are smaller than 4.3 and 8 nm, respectively. Because the critical grain sizes are relatively small for these traditional nanograined refractory alloys, the inverse Hell–Petch relationship can be attributed to the rotation of grain and migration of GB.…”

Section: Resultsmentioning

confidence: 99%

Role of Local FCC Structure to the BCC Polycrystalline NbMoTaWV High‐Entropy Refractory Alloy under Plastic Deformation

2022

Physica Status Solidi (a)

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The molecular dynamics (MD) simulation is used to explore the role of local face‐centered cubic (FCC) structure to the body‐centered cubic (BCC) polycrystalline Nb20.6Mo21.7Ta15.6W21.1V21.0 refractory high‐entropy alloy under plastic deformation. With the grain size of 25.3, 27.9, and 31.9 nm, the dislocation propagation within grains at strains larger than the ultimate strain is the dominant deformation mechanism. With the grain size of 20.1 and 15.6 nm, the dislocation propagation within the grain and the local structural transformation from BCC to the undefined type at the grain/grain boundary (GB) interface are two main deformation mechanisms. With the grain size of 10.0 and 5.2 nm, the local BCC structures of grain atoms significantly become the undefined type, which is the main deformation mechanism during the tensile process. The FCC fraction increases from yield strain to ultimate strain, and remains a FCC fraction of the highest value, indicating the role of local FCC structure is more significant for the cases without dislocation deformation mechanism. Once a large amount of BCC atoms is transformed into the undefined type, some BCC atoms need to transform into local FCC atoms for making their neighbor BCC atoms more local space to decrease the energy barrier for the BCC transformation to the undefined type.

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“…In the case of G3 grain, the grain itself surprisingly disappears in the end. This can be understood through observing the microstructure evolution that the rotation of grains and the slip of grain boundaries are the dominant factors in plastic deformation in CoCrNi MEA with grain size below the critical size [40]. It should be pointed out especially that, the grain boundary between one smaller grain and one larger grain normally has higher energy, and therefore atoms on such a grain boundary can diffuse more easily when the material is being stretched, the disappearance of grain G3 is such an example.…”

Section: Fig 11mentioning

confidence: 99%

The effects of grain size and temperature on mechanical properties of CoCrNi medium-entropy alloy

2023

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In this paper, the molecular dynamics method was used to analyze mechanical properties and microscopic deformation mechanisms of CoCrNi medium-entropy alloy with different average grain sizes at various temperatures. Its elastic modulus and Poisson's ratio were first calculated by the constant pressure molecular dynamics method. It is found that the elastic modulus increases with the average grain size increasing and is reduced at elevated temperatures. However, its Poisson's ratio decreases with the average grain size increasing and is not sensitive to temperatures.Simulations of simple tension were carried out and the results show that: (1) when the average grain size exceeds 15.2 nm, its yield stress and maximum flow stress decreased with the average grain size raising (Hall-Petch relationship), in this situation it is speculated that the dislocation slips and deformation twins within the grains dominate the plastic deformation; (2) when the grain size is smaller than 15.2 nm, the two stress parameters instead increase with the average grain size increasing (Inverse Hall-Petch relationship), such a plastic deformation mechanism is understood mainly due to grain boundaries migrations and grain rotations. In the end, as temperature effects on microscopic deformation mechanisms are concerned, it is found that more dislocations tend to be plugged near grain boundaries which have lower mobility at lower temperatures. Accordingly, the two stress parameters increase as the temperature decreases.

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Micro-mechanism of the effect of grain size and temperature on the mechanical properties of polycrystalline TiAl

Cited by 32 publications

References 43 publications

Grain Distribution for Optimal Strength in Homogeneous and Gradient Nano‐Grained Coppers

Grain Distribution for Optimal Strength in Homogeneous and Gradient Nano‐Grained Coppers

Role of Local FCC Structure to the BCC Polycrystalline NbMoTaWV High‐Entropy Refractory Alloy under Plastic Deformation

The effects of grain size and temperature on mechanical properties of CoCrNi medium-entropy alloy

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