Comparative Evolution of Surface Relieves of Stress-induced Martensite Plates in Shape Memory Alloys with Different Crystalline Structures

Suru, Marius-Gabriel; Moroşanu, Costică; Comaneci, Radu; Mihalache, Elena; Pricop, Bogdan; Lohan, Nicoleta Monica; Baciu, Constantin; Bujoreanu, Leandru-Gheorghe

doi:10.1016/j.matpr.2015.07.440

Cited by 2 publications

(1 citation statement)

References 13 publications

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“…TEM analysis revealed the fact that, due to the nonuniform deformation of HS-HPT processing, a grain size gradient occurred, that increased along cone's generator, from inner diameter to outer diameter of the module [41]. As compared to classically processed Fe-Mn-Si-Cr SMAs, where the widths of stress-induced martensite plates are ranged between 100 and 200 nm [42], at HS-HPT modules martensite plates did not develop to the same magnitudes due to the small size of the grains. Martensite plates (M) observed in figure 8(a) are very fine, with widths that were determined between 50 and 120 nm [43].…”

Section: Structural Analysismentioning

confidence: 99%

A new application of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy, for self-adjustable axial preloading of ball bearings

Paleu

Gurău

Comaneci

et al. 2018

Smart Mater. Struct.

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A new application of Fe-Mn-Si based shape memory alloys (SMAs) was developed under the form of truncated cone-shaped module, for self-adaptive axial preload control in angular contact bearings. The modules were processed by high-speed high-pressure torsion (HS-HPT), from circular crowns cut from axially drilled ingots of Fe-28Mn-6Si-9Cr (mass%) SMA. The specimens were mechanically tested in the hot rolled state, prior to HS-HPT processing, demonstrating free-recovery shape memory effect (SME) and high values for ultimate tensile stress and strain as well as low cycle fatigue life. The HS-HPT modules were subjected to static loading–unloading compression, without/with lubrication at specimen-tool interface, both individually and in different coupling modes. Dry compression cycles revealed reproducible stress plateaus both during loading and unloading stages, being associated with hardness gradient, along cone generator, caused by HS-HPT processing. Constrained recovery tests, performed using compressed modules, emphasized the continuous generation of stress during heating, by one way SME, at a rate of ∼9.3 kPa/%. Dynamic compression tests demonstrated the capability of modules to develop closed stress–strain loops after 50 000 cycles, without visible signs of fatigue. HS-HPT caused the fragmentation of crystalline grains, while compression cycles enabled the formation of ε hexagonal close-packed stress-induced martensite (ε), which is characterized by a high density of stacking faults. Using an experimental setup, specifically designed and manufactured for this purpose, both feasibility and functionality tests were performed using HS-HPT modules. The feasibility tests proved the existence of a general tendency of both axial force and friction torque to increase in time, favoured by the increase of initial preloading force and the augmentation of rotation speed. Functionality tests, performed on two pairs of HS-HPT modules fastened in base-to-base coupling mode, demonstrated the capacity of modules to accommodate high preloads while maintaining both axial force and friction torque at constant values in time. These preliminary results suggest that, for the time being, the modules can operate only as single use applications, more effective during the running-in period. This bevahior recommends HS-HPT modules as a new application of Fe-Mn-Si SMAs, with the potential to be used for the development of new temperature-responsive compression displacement systems.

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Section: Structural Analysismentioning

confidence: 99%

A new application of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy, for self-adjustable axial preloading of ball bearings

Paleu

Gurău

Comaneci

et al. 2018

Smart Mater. Struct.

View full text Add to dashboard Cite

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AFM Evaluation of Pre-Straining Degree Effects on the Dimensions of Stress Induced Martensite Plates in Fe-Mn-Si Based SMAs

Suru

Lohan

Mihalache

et al. 2017

Journal of Testing and Evaluation

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By means of atomic force microscopy (AFM) measurements, the evolution of surface relief characteristics of stress induced martensite plates was investigated on the surface of polished Fe-14Mn-6Si-9Cr-5Ni and Fe–28Mn–6Si–5Cr (mass. %) shape memory alloys (SMAs), subjected to various pre-straining degrees. Pre-straining degree was chosen as an independent variable, considering its influence on the reverse transformation of martensite. The specimens were cast by means of a levitation induction furnace and hot rolled to 1 mm-thickness in order to better reveal the shape memory phenomena. The specimens, cut by spark erosion to “dog-bone” shapes, were pre-strained by means of a tensile testing machine at room temperature (RT). The gauges of elongated specimens were analyzed by AFM. Qualitative 2D analyses were performed on AFM micrographs. Quantitative evaluations were based on systematic dimensional measurements of martensite profiles, allowing the determination of the average values of plate widths and heights for four pre-straining degrees of the two SMA systems under study. The variation tendencies of average values of martensite plate widths and heights with increasing the pre-straining were examined under the form of increasing rates of the plate widths and heights. The results show that, for the two SMA systems studied, the average widths and heights of stress-induced martensite plates varied between 80 and 188 nm for Fe-14Mn-6Si-9Cr-5Ni and between 101 and 192 nm for Fe-28Mn-6Si-5Cr. These dimensions experienced an increasing tendency with pre-straining degree, with a rate of about 30 nm/ % pre-strain.

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Comparative Evolution of Surface Relieves of Stress-induced Martensite Plates in Shape Memory Alloys with Different Crystalline Structures

Cited by 2 publications

References 13 publications

A new application of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy, for self-adjustable axial preloading of ball bearings

A new application of Fe-28Mn-6Si-5Cr (mass%) shape memory alloy, for self-adjustable axial preloading of ball bearings

AFM Evaluation of Pre-Straining Degree Effects on the Dimensions of Stress Induced Martensite Plates in Fe-Mn-Si Based SMAs

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