Effect of hydrogen on the tensile strength of aged Ni–Ti superelastic alloy

Gamaoun, Fehmi; Ltaief, Montassarbellah; Bouraoui, Tarak; Zineb, Tarak Ben

doi:10.1177/1045389x11423427

Cited by 39 publications

(24 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 The influence of the hydrogen absorption probably contributes to the observed changes in mechanical properties. 20 No correlation between the surface roughness and friction has been found, and similar was reported previously. 23 Frictional resistance does not directly correlate to the surface roughness, but it depends on the type of the material, as TMA wires which have bigger surface roughness than nickel-titanium wires have lower frictional resistance.…”

Section: Discussionsupporting

confidence: 86%

“…19 Furthermore, when immersed into a more acid solution, the wire may become brittle due to the penetration of the hydrogen into the NiTi wire. 20 The type of coating studied on the as-received samples revealed a higher elastic modulus and yield strength of the rhodium-coated wires during loading; however, no differences were found during unloading, i.e., upon recovery of the memory shape of the wires, which is important for clinical performance. 21 The observed differences in mechanical properties were probably generated during different manufacturing conditions.…”

Section: Discussionmentioning

confidence: 88%

See 1 more Smart Citation

The coating of a NiTi alloy has a greater impact on the mechanical properties than the acidity of saliva

Acev¹,

Katić²,

Turco³

et al. 2018

Mater. Tehnol.

View full text Add to dashboard Cite

The aim of this study was to evaluate the influence of the acidity of saliva on changes to the surface roughness, friction and microhardness of NiTi alloys with various coatings. Three types of commercially available NiTi archwires: uncoated, rhodium coated and nitrified (dimension 0.508×0.508 mm, 10 cm long) were immersed in 10 mL of artificial saliva with the pH ranging from 4.8 to 6.6 for a period of 28 d. Surface roughness, friction and microhardness were analyzed and compared to the unexposed as-received wires. These mechanical properties were influenced by the wire coating with a moderate-to-high effect size (p£0.005; h 2 =0.132-0.309). The uncoated wire had a lower maximum roughness depth after exposure to pH 6.6 and 5.5 than the unexposed wire (p=0.026; h 2 =0.346). The friction was significantly increased only in the rhodium-coated NiTi at pH 4.8 compared to the lower acidities and the unexposed wire (p=0.005; h 2 =0.437). No correlation was found between pH, surface roughness, friction and microhardness, respectively. The coating of a NiTi alloy has a greater impact on the mechanical properties than the acidity does. A rhodium coating makes the alloy harder, induces a rougher surface and more friction. Nitrification does not alter the alloy as much. The relation between acidity and mechanical properties is not linear. A high acidity of 4.8 induces a high friction, but only in rhodium-coated NiTi. A lower acidity does not change the friction significantly.Cilj {tudije je bil ovrednotiti vpliv kislosti sline na spremembe povr{inske hrapavosti, trenja in mikrotrdote biokompatibilne NiTi zlitine z razli~nimi opla{~enji. Avtorji so za svoje preiskave uporabili tri vrste komercialno dosegljivih NiTi ortodontskih pritrjevalnih`ic: neopla{~eno, opla{~eno z rodijem in nitrificirano (dimenzij 0,508 mm × 0,508 mm, dol`ine 10 cm). @ice so 28 dni potapljali v 10 ml umetne sline s pH vrednostjo med 4,8 in 6,6. Nato so izvedli analize povr{inske hrapavosti, trenja in mikrotrdote v slino namo~enih`ic in jih primerjali z nenamo~enimi izhodnimi`icami. Na mehanske lastnosti je imelo opla{~enje`ic zmeren do znaten vpliv (p£0.005; h 2 =0,132-0,309). Neopla{~ena`ica je imela manj{o maksimalno globino hrapavosti po izpostavitvi pH 6,6 in 5,5 kot`ica, ki slini ni bila izpostavljena (p=0,026; h 2 =0,346). Trenje se je znatno pove~alo samo pri z rodijem opla{~eni NiTi`ici pri pH 4,8 v primerjavi z manj{imi kislostmi in pri s slino neizpostavljeni`ici (p=0,005; h 2 =0,437). Avtorji niso na{li nobene povezave med pH, povr{insko hrapavostjo, trenjem in mikrotrdoto. Opla{~enje NiTi zlitine ima ve~ji vpliv na mehanske lastnosti kot kislost. Opla{~enje z rodijem naredi zlitino tr{o, inducira bolj grobo povr{ino in pove~a trenje. Nitrifikacija bistveno ne spremeni zlitine. Zveza med kislostjo in mehanskimi lastnostmi ni linearna. Velika kislost 4,8 inducira trenje, vendar samo pri z rodijem opla{~enih NiTi`icah. Manj{a kislost pomembno ne spremeni trenja.

show abstract

Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 88%

The coating of a NiTi alloy has a greater impact on the mechanical properties than the acidity of saliva

Acev¹,

Katić²,

Turco³

et al. 2018

Mater. Tehnol.

View full text Add to dashboard Cite

show abstract

“…Here, it is well known that the hydrogen embrittlement behavior of metals is affected not only by the hydrogen content but also the hydrogen state, and the hydrogen state in metals is reflected by the hydrogen thermal desorption behavior. It has been reported that differences in the hydrogen state of the Ni-Ti alloys can change their hydrogen embrittlement behavior (Yokoyama et al 2007a(Yokoyama et al , 2009(Yokoyama et al , 2012Ogawa et al 2005a;He et al 2004;Gamaoun et al 2011). As shown in Fig.…”

Section: -H Immersionmentioning

confidence: 94%

Hydrogen embrittlement behavior of Ni-Ti shape memory alloy with different microstructures in acidic fluoride solution

Ogawa

Yokozawa

Oda

et al. 2015

Int J Mech Mater Eng

View full text Add to dashboard Cite

Background: It is important to investigate the mechanism for the hydrogen embrittlement of Ni-Ti alloys in acidic fluoride solutions to improve the reliability and safety of these alloys as dental devices. Therefore, the hydrogen embrittlement behavior of Ni-Ti shape memory alloy immersed in acidic fluoride solution was investigated with a focus on the constituent phase in the microstructure of the alloy in this study. Methods: Three microstructures with different phases (parent single phase, mixture of parent and martensite phases, and martensite single phase) were prepared by tensile loading and unloading. The specimens were immersed separately in 50 mL of 0.2 % acidulated phosphate fluoride (APF) solution with pH 5.0 at room temperature (25°C) for various periods. Results: After immersion for 2 h, the tensile strengths of all the specimens were not significantly changed with respect to those of the non-immersed specimens. After immersion for 4 h, the tensile strengths of all the specimens immersed were decreased with respect to those of the non-immersed specimens, and the tensile strength of the martensite single phase specimen (C) was higher than that of parent single phase specimen (A) and the parent/martensite mixed phase specimen (B). After immersion for 6 h, the tensile strengths of all the specimens were decreased with respect to those of the specimens immersed for 4 h, and the tensile strength of specimen B was lower than that of specimens A and C. Conclusions: The susceptibility to hydrogen embrittlement of the Ni-Ti shape memory alloy with a microstructure including the parent phase tends to be high when the degree of corrosion is not significantly different for the alloy microstructure. Moreover, the effect of corrosion on the tensile strength of Ni-Ti shape memory alloy is significant when the microstructure includes the martensite phase. Hence, the significant degradation of tensile strength observed for specimen B was probably caused by a synergistic effect of hydrogen absorption and corrosion.

show abstract

“…However, we notice that the hardening-like slope of the phase-transformation pseudo-plateau grows slightly and a minor reduction of the plateau is detected. According to our previous results [5][6][7], this could be attributed to the hindrance of the austenite transformation by the absorbed hydrogen. In addition, this result indicates that after 3 h of immersion, the amount of diffused hydrogen is not enough to cause an increase in the critical stress for introducing martensite or to generate an embrittlement during the austenite transformation.…”

Section: Methodsmentioning

confidence: 99%

Effect of Hydrogen on the Stress Relaxation of Aged NiTi Shape Memory Alloys

2016

View full text Add to dashboard Cite

The susceptibility of the NiTi shape memory alloy to relaxation after the hydrogen charging in an aqueous solution has been investigated with respect to ageing during one to six days in air at room temperature. The orthodontic wires have been prepared by immersing in a 0.9% NaCl solution for 3 h, under applied current density of 10 A/m 2 and then relaxed with an imposed deformation in a fully austenite state of structure and in a state with 1/3 and 2/3 of the martensite volume fraction. Through the stress relaxation, the hydrogen-charged specimen has shown a significant decrease of the stress, compared to the non-immersed alloy, when the imposed deformation was located in the plateau of the austenite-martensite transformation. It was also found that a longer ageing period is important and the properties of the wires with longer stress relaxation are similar to the those of non-charged wires. Nevertheless, no difference has been detected between the as-received and the as-charged specimens when the imposed deformation was located in the elastic deformation region of the fully austenitic structure. This behavior is attributed to the effect of the gradient of absorbed hydrogen, existing between the surface and the center axis of the studied wires, which facilitates the mobility of the martensite bands during the stress relaxation.

show abstract

Effect of hydrogen on the tensile strength of aged Ni–Ti superelastic alloy

Cited by 39 publications

References 27 publications

The coating of a NiTi alloy has a greater impact on the mechanical properties than the acidity of saliva

The coating of a NiTi alloy has a greater impact on the mechanical properties than the acidity of saliva

Hydrogen embrittlement behavior of Ni-Ti shape memory alloy with different microstructures in acidic fluoride solution

Effect of Hydrogen on the Stress Relaxation of Aged NiTi Shape Memory Alloys

Contact Info

Product

Resources

About