Deformation and damage mechanisms in an α/β 6242 Ti alloy in fatigue, dwell-fatigue and creep at room temperature. Influence of internal hydrogen

Studies have been conducted as to the effect of Cu, Mn, Fe concentration changes in Al-Cu-Mn-Fe-Ti alloy, the conditions of thermal and deformational treatment of ingots and extruded rods 40 mm in diameter on the microstructure, phase composition and mechanical properties. It has been determined that changing Al-6.3Cu-0.3Mn-0.17Fe-0.15Ti alloy to Al-6.5Cu-0.7Mn-0.11Fe-0.15Ti causes an increase in the strength characteristics of extruded rods at the room temperature both after molding and in tempered and aged conditions, irrespective of the conditions of thermal treatment of the initial ingot (low-temperature annealing 420 °С for 2 h, or high-temperature annealing at 530 °С for 12 h). Increasing the extruding temperature from 330 to 480 °С, along with increasing Cu, Mn and decreasing Fe in the alloy Al-Cu-Mn-Ti, is accompanied by the increased level of ultimate strength in a quenched condition by 25% to 410 MPa, irrespective of the annealing conditions of the original ingot. An opportunity to apply the Al-6.3Cu-0.3Mn-0.17Fe-0.15Ti alloy with low-temperature annealing at 420 °С for 2 h and the molding temperature of 330 °С has been found to produce rods where, in the condition of full thermal treatment (tempering at 535 °С + aging at 200 °С for 8 hours), a structure is formed that ensures satisfactory characteristics of high temperature strength by resisting to fracture for more than 100 hours at 300 °С and 70 MPa.

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Microstructures and Interfaces in Melt-Growth Al2O3-Ln2O3 Based Eutectic Composites

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.45.1377 ◽

2006 ◽

Vol 45 ◽

pp. 1377-1384 ◽

Cited By ~ 4

Author(s):

Léo Mazerolles ◽

N. Piquet ◽

M.F. Trichet ◽

Michel Parlier

Keyword(s):

Fracture Toughness ◽

Single Crystal ◽

Room Temperature ◽

Eutectic Composition ◽

High Strength ◽

Ternary Systems ◽

Growth Conditions ◽

Temperature Influence ◽

Directionally Solidified ◽

Orientation Relationships

Directionally solidified oxide eutectic ceramics were prepared from Al2O3, Ln2O3 and ZrO2 based binary or ternary systems. Their microstructures consist of continuous networks of single-crystal Al2O3 and oxide compounds (LnAlO3, Ln3Al5O12) which interpenetrate without grain boundaries. The outstanding stability of these microstructures gives rise to a high strength and creep resistance at high temperature. Influence of growth conditions on the morphology of the as-obtained microstructures was studied. Preferred growth directions, orientation relationships between phases and single-crystal homogeneity of specimen were revealed. Low residual stresses were measured in the binary eutectics and fracture toughness at room temperature was improved by the addition of zirconia at a eutectic composition in ternary systems.

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Ductilization of a Ni3(Si,Ti) Intermetallic Alloy by Addition of Interstitial Type Elements

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.409.321 ◽

2011 ◽

Vol 409 ◽

pp. 321-326

Author(s):

Hisashi Kosaka ◽

Yasuyuki Kaneno ◽

Takayuki Takasugi

Keyword(s):

Fracture Surface ◽

Fracture Mode ◽

Room Temperature ◽

Tensile Ductility ◽

Tensile Elongation ◽

Intermetallic Alloy ◽

Intermediate Temperature ◽

Transgranular Fracture ◽

Ti Alloy ◽

Brittle Intergranular Fracture

The effect of a concomitant doping of interstitial type elements boron (B) and carbon (C), and boron (B) and nitrogen (N) on tensile properties of a Ni3(Si,Ti) intermetallic alloy was investigated in the temperature range between room temperature and 973 K. It was found that the concomitant doping of (C/B) and (N/B) remarkably improved the intermediate-temperature tensile elongation of the Ni3(Si,Ti) alloy compared with the simple doping of B or C. It was also shown that the fracture surface of the alloy doped with (C/B) and (N/B) exhibited the ductile transgranular fracture mode while that of the alloy doped with only B showed a brittle intergranular fracture mode at 773 K. These results clearly indicate that the concomitant doping of the interstitial type elements are useful for improving the intermediate-temperature tensile ductility of the Ni3(Si,Ti) alloy.

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Effects of External and Internal Hydrogen on Tensile Properties of Austenitic Stainless Steels Containing Additive Elements

Volume 6B: Materials and Fabrication ◽

10.1115/pvp2015-45740 ◽

2015 ◽

Author(s):

Hisatake Itoga ◽

Hisao Matsunaga ◽

Junichiro Yamabe ◽

Saburo Matsuoka

Keyword(s):

Stainless Steels ◽

Room Temperature ◽

Austenitic Stainless Steels ◽

Hydrogen Gas ◽

Nitrogen Gas ◽

Material Compatibility ◽

Internal Hydrogen ◽

The Stability ◽

Reduction Of Area ◽

Nickel Equivalent

Effect of hydrogen on the slow strain rate tensile (SSRT) properties of five types of austenitic stainless steels, which contain small amounts of additive elements (e.g., nitrogen, niobium, vanadium and titanium), was studied. Some specimens were charged by exposing them to 100 MPa hydrogen gas at 543 K for 200 hours. The SSRT tests were carried out under various combinations of specimens and test atmospheres as follows: (i) non-charged specimens tested in air at room temperature (RT), (ii) non-charged specimens tested in 0.1 MPa nitrogen gas at 193 K, (iii) hydrogen-charged specimens tested in air at RT, (iv) hydrogen-charged specimens tested in 0.1 MPa nitrogen gas at 193 K, and (v) non-charged specimens tested in 115 MPa hydrogen gas at RT. In the tests without hydrogen (i.e., cases (i) and (ii)), the reduction of area (RA) was nearly constant in all the materials, regardless of test temperature. In contrast, in the tests of internal hydrogen (cases (iii) and (iv)), RA was much smaller at 193 K than at RT in all the materials. It was revealed that the susceptibility of the materials to hydrogen embrittlement (HE) can successfully be estimated in terms of the nickel equivalent, which represents the stability of austenite phase. The result suggested that the nickel equivalent can be used for evaluating the material compatibility of austenitic stainless steels for hydrogen service.

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The rupture life prediction in cold dwell fatigue of Ti-6Al-4V based on the creep deformation

MATEC Web of Conferences ◽

10.1051/matecconf/202032111071 ◽

2020 ◽

Vol 321 ◽

pp. 11071

Author(s):

Yutaro Ota ◽

Tomomichi Ozaki ◽

Keiji Kubushiro.O

Keyword(s):

Creep Deformation ◽

Minimum Creep Rate ◽

Life Prediction ◽

Dwell Time ◽

Room Temperature ◽

Rupture Life ◽

Ti Alloys ◽

Dwell Fatigue ◽

Strain Change ◽

Long Time

Titanium a lloys have been found that the fatigue strength of Ti alloys decreases due to cold dwell fatigue (CDF) at room temperature. Ti and Ti alloys generate creep deformation at room temperature (T/Tm = 0.15). Thus, it is considered that creep affects the reduction in fatigue life in CDF tests. This research intends to clarify the effects of long time dwell under tensile stress and rupture life prediction from the view of creep deformation in CDF characteristics of Ti-6Al-4V. Rupture cycle decreased with increase of dwell time. Additionally, lower limit of rupture life ratio “NCDF/NLCF” was defined from rupture in creep test if it was assumed that creep test was extremely long time dwell CDF test. When strain change in whole dwell time was extracted in CDF tests, strain change was like creep curves and minimum creep rate changed depending on dwell time. Minimum creep rate was calculated by the formula based on experimental results, and then rupture time was calculated by Monkman-grant relationship. All of rupture cycle predictions were in factor of 2. Therefore, rupture cycle and time can be calculated if dwell time is known in CDF tests.

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Nanowire Tunnel Field Effect Transistors at High Temperature

Journal of Integrated Circuits and Systems ◽

10.29292/jics.v8i2.381 ◽

2013 ◽

Vol 8 (2) ◽

pp. 110-115

Author(s):

Márcio D. V. Martino ◽

Felipe S. Neves ◽

Paula Ghedini Der Agopian ◽

João Antonio Martino ◽

Rita Rooyackers ◽

...

Keyword(s):

Field Effect ◽

Room Temperature ◽

Field Effect Transistors ◽

Drain Current ◽

Transport Mechanisms ◽

Temperature Influence ◽

Subthreshold Slope ◽

Band To Band Tunneling ◽

Trap Assisted Tunneling ◽

Working Principle

The aim of this work is to study how the performance of nanowire tunnel field effect transistors (TFETs) is influenced by temperature variation. First of all, simulated energy band diagrams were presented to justify its fundamental working principle and this analysis was compared to experimental data obtained for temperature ranging from 300 to 420 K. This methodology was performed for different nanowire diameters and bias conditions, leading to a deep investigation of parameters such as the ratio of on-state and off-state current (ION/IOFF) and the subthreshold slope (S). Three different transport mechanisms (band-to-band tunneling, Shockley-Read-Hall generation/recombination and trap-assisted tunneling) were highlighted to explain the temperature influence on the drain current. As the final step, subthreshold slope values for each configuration were compared to the room temperature. Therefore, it was observed that larger nanowire diameters and lower temperatures tended to increase ION/IOFF ratio. Meanwhile, it was clear that band-to-band tunneling prevailed for higher gate voltage bias, resulting in a much slighter temperature effect on the drain current.

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Why titanium alloys withstand more strain under dwell-fatigue than under fatigue?

MATEC Web of Conferences ◽

10.1051/matecconf/202032111080 ◽

2020 ◽

Vol 321 ◽

pp. 11080

Author(s):

S. Hémery ◽

A. Naït-Ali ◽

C. Lavogiez ◽

P. Villechaise

Keyword(s):

Crack Initiation ◽

Plastic Strain ◽

Room Temperature ◽

Maximum Stress ◽

Fourier Transforms ◽

Stress And Strain ◽

Cyclic Testing ◽

Applied Loading ◽

Dwell Fatigue ◽

Number Of Cycles

Experimental observations reveal that crack initiation proceeds at a reduced number of cycles if a load hold at maximum stress is introduced during cyclic testing. Although this feature was extensively investigated and stems from the occurrence of room temperature creep, other differences between fatigue and dwell-fatigue behaviors are still to be clarified. In particular, a higher plastic strain is cumulated prior to failure if the load hold is present. This observation highlights differences in the deformation behavior depending on the applied loading. The present article reports an investigation of this point using Fast-Fourier transforms based crystal plasticity simulations of the stress and strain field. Significant differences were evidenced and discussed in light of experimental results reported in the literature. In particular, the occurrence of crack initiation for different cumulated plastic strain depending on the loading conditions is elucidated.

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