Influences of Potential and pH on Initiation of Environment-Assisted Cracking of Ti&amp;ndash;6Al&amp;ndash;4V

Haruna, Takumi; Hamasaki, Masaya; Shibata, Toshio

doi:10.2320/matertrans.46.2190

Cited by 8 publications

(8 citation statements)

References 17 publications

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“…These ndings suggested that the surface property relating to the process of hydrogen absorption was not affected by Al, but was affected by Ti. Our research group also previously produced an EAC map of Ti-6Al-4V alloy 13) and a hydrogen absorption map of Ti 14) ; and revealed that these Ti-Al alloys, including Ti, absorbed hydrogen most severely in the Ti ion stable region. Conversely, no stable regions for chemical species except for hydrogen could be identi ed on the potential-pH diagrams of the Ni/H 2 O and Ti/H 2 O systems that corresponded to the region of severe EAC susceptibility.…”

Section: Surface Conditions Of Tini Alloy For Absorption Of Hydrogenmentioning

confidence: 99%

Role of the Electrochemical Potential and Solution pH to Environment-Assisted Cracking of Super-Elastic TiNi Alloy

et al. 2016

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The susceptibility to environment-assisted cracking (EAC) of super-elastic TiNi alloy was investigated as a function of the electrochemical potential and solution pH. The investigation was conducted using a slow-strain-rate tensile test apparatus with a potentiostat. The test solutions were sulfate solutions with various pH values adjusted by H 2 SO 4 or NaOH. The alloy deforming under cathodic reaction fractured under the relatively small strain where the alloy was in the stress-induced martensitic phase. A larger EAC susceptibility was obtained at lower potential and lower pH, which indicates that this is a general feature of hydrogen embrittlement. The severe EAC region of TiNi alloy was different from that of TiAl alloy. The EAC susceptibility was strongly correlated with the cathodic charge density, irrespective of the pH or potential: a charge density below 0.025 MC m −2 yielded almost no EAC; however, above 0.025 MC m −2 EAC was induced, and the EAC susceptibility was independent of the charge density. Hydrogen in solid-solution state was detected in the alloy at a charge density below 0.025 MC m .

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Section: Surface Conditions Of Tini Alloy For Absorption Of Hydrogenmentioning

confidence: 99%

Role of the Electrochemical Potential and Solution pH to Environment-Assisted Cracking of Super-Elastic TiNi Alloy

et al. 2016

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“…For titanium alloys, such as Ti6Al-4V alloy, however, the hydrogen absorption behavior is not necessarily consistent with the electrochemical behavior. 21,22) In addition, the hydrogen absorption behavior of Ti-6Al-4V alloy strongly depends on the type of solution. In this case, the hydrogen absorption behavior appears to depend on the surface conditions, including the nature of surface oxide films on titanium alloys.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Absorption and Thermal Desorption Behavior of Ni-Ti Superelastic Alloy Immersed in Neutral NaCl and NaF Solutions under Applied Potential

et al. 2009

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The hydrogen absorption and thermal desorption behavior of Ni-Ti superelastic alloy immersed in neutral NaCl and NaF aqueous solutions at 25C under an applied cathodic potential for 2 h have been systematically investigated by hydrogen thermal desorption analysis. The critical potential for hydrogen absorption is independent of the type and concentration of solution. The amount of absorbed hydrogen increases with decreasing applied potential, although it is only slightly changed by the type of solution. The amount of hydrogen desorbed at low temperatures, for the alloy immersed in NaF solutions, is larger than those in NaCl solutions, suggesting that the type of solution affects the hydrogen states in the alloy. The present results indicate that for Ni-Ti superelastic alloy, compared with titanium and its alloys, the critical potential for hydrogen absorption is located in a more noble direction, and the amount of absorbed hydrogen is large in NaCl and NaF solutions. Thus, the hydrogen embrittlement of Ni-Ti superelastic alloy probably occurs more readily than those of titanium and its alloys in NaCl and NaF solutions.

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“…These results suggest that for Ti-6Al-4V alloy, corrosion does not necessarily lead to hydrogen absorption in fluoride solution, although for commercial pure titanium, corrosion leads to hydrogen absorption. 17) In aqueous Na 2 SO 4 solutions with pH ranging from 3.0 to 7.0, as reported by Haruna et al, 18) hydrogen-induced environment-assisted cracking of Ti-6Al-4V alloy does not occur even under a cathodic potential of À2:0 V. In addition, we have recently demonstrated that the hydrogen absorption of Ti-6Al-4V alloy occurs below the cathodic potential of À1:9 V in neutral 2.0% NaF solution. 16) In the present study, however, Ti-6Al-4V alloy absorbed substantial amounts of hydrogen in APF solutions with concentration of 0.4% and higher under a corrosion potential of À1:0 V. Furthermore, although electrochemical behavior was not significantly different between 1.5% and 2.0% APF solutions, the amount of absorbed hydrogen depended on the concentration of APF solution.…”

Section: Discussionmentioning

confidence: 96%

Relationship between Hydrogen Absorption and Corrosion Behavior of Ti-6Al-4V Alloy Immersed in Acidic Fluoride Solutions

et al. 2009

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The relationship between hydrogen absorption and the corrosion behavior of Ti-6Al-4V alloy has been examined by immersing the alloy in acidulated phosphate fluoride (APF) solution with various concentrations. Upon immersion in 0.1 mass% APF solution, no hydrogen absorption is observed despite the occurrence of general corrosion. In 0.2% APF solution, slight hydrogen absorption occurs soon after immersion, and then the surface of the specimen becomes uniformly covered with a crystalline corrosion product (Na 3 AlF 6 ), thereby inhibiting further hydrogen absorption. In APF solutions with concentrations higher than 0.4%, the amount of absorbed hydrogen increases with increasing concentration of APF solution and immersion time. The type and morphology of corrosion products sensitively depend on the concentration of APF solution. Upon immersion in 0.4% APF solution, crystalline and massive Na 3 AlF 6 are observed on the surface of the specimen. In 1.0% and 1.5% APF solutions, Na 3 AlF 6 with a foldlike shape and granular Na 3 AlF 6 and Na 3 TiF 6 are observed. In 2.0% APF solution, only granular Na 3 TiF 6 is observed. The corrosion potentials and anodic polarization curves are analogous in all APF solutions except the 0.2% and 0.4% APF solutions. In contrast, the current density of cathodic polarization curves increases with the concentration of APF solution. The results of the present study suggest that the corrosion products play an important role in the hydrogen absorption behavior of Ti-6Al-4V alloy.

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Influences of Potential and pH on Initiation of Environment-Assisted Cracking of Ti–6Al–4V

Cited by 8 publications

References 17 publications

Role of the Electrochemical Potential and Solution pH to Environment-Assisted Cracking of Super-Elastic TiNi Alloy

Role of the Electrochemical Potential and Solution pH to Environment-Assisted Cracking of Super-Elastic TiNi Alloy

Hydrogen Absorption and Thermal Desorption Behavior of Ni-Ti Superelastic Alloy Immersed in Neutral NaCl and NaF Solutions under Applied Potential

Relationship between Hydrogen Absorption and Corrosion Behavior of Ti-6Al-4V Alloy Immersed in Acidic Fluoride Solutions

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