Pathways Towards Grain Boundary Engineering for Improved Structural Performance in Polycrystalline Co–Ni–Ga Shape Memory Alloys

Lauhoff, C.; Vollmer, Malte; Krooß, P.; Киреева, И. В.; Chumlyakov, Yuriy; Niendorf, Т.

doi:10.1007/s40830-018-00204-3

Cited by 11 publications

(12 citation statements)

References 38 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Especially in the vicinity of triple junctions, this incompatibilities lead to stress concentrations, which are thought to be responsible for a detrimental superelastic behavior [32] and for the initiation of intergranular fracture [29]. Similar observations have also been made in Cubased SMAs [33][34][35][36][37][38] and Co-based SMAs [39,40]. Moreover, it was shown that the superelastic performance significantly can be improved in an oligocrystalline state, i.e., in case the mean grain size exceeds the cross section of the samples [11,31,41].…”

Section: Introductionmentioning

confidence: 61%

“…It can be seen that stress concentrations at the upper part of the grain boundary are accommodated by martensite plates with different orientations. This is likely caused by the grain boundary morphology leading to stress states known from grain boundary triple points [35,39]. In contrast, the martensite plates in the grain center run across the grain boundary and expand up to 400 lm into the right grain.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

Bauer

Vollmer

Niendorf

2021

Shap. Mem. Superelasticity

Self Cite

View full text Add to dashboard Cite

In situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

show abstract

Section: Introductionmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

Bauer

Vollmer

Niendorf

2021

Shap. Mem. Superelasticity

Self Cite

View full text Add to dashboard Cite

show abstract

“…structures of relatively brittle and anisotropic SMAs, e.g. Co-Ni-Ga [12,13,16]. Furthermore, martensite plates remain stabilized after final unloading in these particular areas (Figure 5).…”

Section: Resultsmentioning

confidence: 99%

“…Unfortunately, polycrystalline material suffers premature failure, i.e. particularly intergranular cracking upon thermo-mechanical loading and/or processing [1,12,13]. In microstructures without preferred grain orientation, the pronounced anisotropy of the transformation behavior [14] results in incompatibilities at grain boundaries (GBs) between grains of different crystallographic orientations.…”

Section: Introductionmentioning

confidence: 99%

Excellent superelasticity in a Co-Ni-Ga high-temperature shape memory alloy processed by directed energy deposition

Lauhoff

Sommer

Vollmer

et al. 2020

Materials Research Letters

Self Cite

View full text Add to dashboard Cite

A Co-Ni-Ga high-temperature shape memory alloy has been additively manufactured by directed energy deposition. Due to the highly anisotropic microstructure, i.e. columnar grains featuring a strong near-001 texture in build direction, the as-built material is characterized by a very low degree of constraints and, thus, shows excellent superelasticity without conducting a post-process heat treatment. As characterized by in situ deformation testing and post-mortem microstructural analysis, additive manufacturing employing directed energy deposition seems to be highly promising for processing of shape memory alloys, which often suffer difficult workability. IMPACT STATEMENTThe present work establishes a new pathway towards realization of high performance shape memory alloys by additive manufacturing and, thus, will stimulate further research in this field directed towards application.

show abstract

“…This was attributed to hardening of the matrix, changes of lattice parameters, and different selection of the martensite variants 12,14–16 . However, other SMA systems show significant improvements of the functional properties only if the grains completely cover the entire cross-section of the samples, for example, copper-based SMAs 17–23 , cobalt-based SMAs 24,25 , and iron-based SMAs 26–35 . Investigations by Ueland and Schuh 17–19 showed that grain boundary triple junctions as well as large grain boundary fractions have a detrimental effect on the pseudoelastic performance of polycrystalline Cu–Zn–Al and Cu–Al–Ni.…”

Section: Introductionmentioning

confidence: 99%

Promoting abnormal grain growth in Fe-based shape memory alloys through compositional adjustments

et al. 2019

Self Cite

View full text Add to dashboard Cite

Iron-based shape memory alloys are promising candidates for large-scale structural applications due to their cost efficiency and the possibility of using conventional processing routes from the steel industry. However, recently developed alloy systems like Fe–Mn–Al–Ni suffer from low recoverability if the grains do not completely cover the sample cross-section. To overcome this issue, here we show that small amounts of titanium added to Fe–Mn–Al–Ni significantly enhance abnormal grain growth due to a considerable refinement of the subgrain sizes, whereas small amounts of chromium lead to a strong inhibition of abnormal grain growth. By tailoring and promoting abnormal grain growth it is possible to obtain very large single crystalline bars. We expect that the findings of the present study regarding the elementary mechanisms of abnormal grain growth and the role of chemical composition can be applied to tailor other alloy systems with similar microstructural features.

show abstract

Pathways Towards Grain Boundary Engineering for Improved Structural Performance in Polycrystalline Co–Ni–Ga Shape Memory Alloys

Cited by 11 publications

References 38 publications

Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

Excellent superelasticity in a Co-Ni-Ga high-temperature shape memory alloy processed by directed energy deposition

Promoting abnormal grain growth in Fe-based shape memory alloys through compositional adjustments

Contact Info

Product

Resources

About