scholarly journals Influence of annealing on the functional properties of the NiTi alloy produced by wire arc additive manufacturing

2022 ◽  
Vol 1213 (1) ◽  
pp. 012002
Author(s):  
N Resnina ◽  
I A Palani ◽  
S Belyaev ◽  
R Bikbaev ◽  
Shalini Singh ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Martensitic Transformation ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Niti Alloy ◽  
Strain Variation ◽  
Recoverable Strain ◽  
Niti Phase ◽  
Working Length ◽  
Wire Arc Additive Manufacturing

Abstract The influence of the annealing temperature on the recoverable strain variation on cooling and heating under a stress of 200 MPa was studied in the NiTi samples produced by wire arc additive manufacturing. The samples including the Ni-rich NiTi layer in the working length were annealed for 10 hours at various temperature from 450 to 600 °C. It is shown that an increase in annealing temperature leads to non-monontonic variation in the recoverable strain. This is caused by an increase in annealing temperature from 450 to 550 °C increases the volume fraction of Ni4Ti3 precipitates. As a result, the volume fraction of the NiTi phase undergoing the martensitic transformation and recoverable strain decrease. An increase in annealing temperature from 550 to 600 °C leads to a dissolving the Ni4Ti3 precipitates and formation of the Ni3Ti2 precipitates that increases the volume fraction of the NiTi phase and the recoverable strain.

scholarly journals The strain variation during the isothermal B2→B19’ martensitic transformation in the quenched or annealed Ni51Ti49 alloy

2022 ◽  
Vol 1213 (1) ◽  
pp. 012005
Author(s):  
A Ivanov ◽  
A Gabrielian ◽  
S Belyaev ◽  
N Resnina ◽  
V Andreev
Keyword(s):  
Martensitic Transformation ◽  
Volume Fraction ◽  
Isothermal Holding ◽  
Isothermal Transformation ◽  
Annealed Sample ◽  
Strain Variation ◽  
Maximum Value ◽  
Niti Phase ◽  
Alloy Heat ◽  
Isothermal Martensitic Transformation

Abstract The strain variation during the isothermal holding under constant stress was studied in the quenched or annealed Ni51Ti49 alloy samples. The isothermal strain variation was found in both samples and this strain was completely recovered on subsequent unloading and heating. This allowed to conclude that the strain variation on holding was caused by the isothermal martensitic transformation. It was found that the maximum value of isothermal strain depended on the alloy heat treatment. This value was equal to 0.5 % in annealed sample and it was equal to 6 % in quenched sample. It was assumed that the formation of the Ni4Ti3 phase during annealing led to a decrease in concentration of substitutional Ni atoms in NiTi phase that were responsible for the isothermal transformation. As a result, the less volume fraction of the martensite formed during holding that supresses the strain variation in annealed samples.

scholarly journals Additive Manufacturing with Superduplex Stainless Steel Wire by CMT Process

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 272 ◽  
Author(s):  
Malin Lervåg ◽  
Camilla Sørensen ◽  
Andreas Robertstad ◽  
Bård M. Brønstad ◽  
Bård Nyhus ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Volume Fraction ◽  
Steel Wire ◽  
Oil And Gas Industry ◽  
Secondary Phases ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Σ Phase ◽  
Wide Range ◽  
Wire Arc Additive Manufacturing

For many years, the oil and gas industry has utilized superduplex stainless steels due to their high strength and excellent corrosion resistance. Wire arc additive manufacturing (WAAM) was used with superduplex filler wire to create walls with different heat input. Due to the multiple heating and cooling cycles during layer deposition, brittle secondary phases may form such as intermetallic sigma (σ) phase. By inspecting deposited walls within wide range of heat inputs (0.40–0.87 kJ/mm), no intermetallic phases formed due to low inter-pass temperatures used, together with the high Ni content in the applied wire. Lower mechanical properties were observed with high heat inputs due to low ferrite volume fraction, precipitation of Cr nitrides and formation of secondary austenite. The walls showed good toughness values based on both Charpy V-notch and CTOD (crack tip opening displacement) testing.

Shape Memory Characteristics of NiTi Alloy Wire under Various Constrained Stresses

2012 ◽  
Vol 567 ◽  
pp. 135-140 ◽  
Author(s):  
Yan Feng Li ◽  
X.J. Mi ◽  
Xiang Qian Yin ◽  
H.F. Xie
Keyword(s):  
Shape Memory ◽  
Annealing Temperature ◽  
Volume Fraction ◽  
Niti Alloy ◽  
Transformation Temperatures ◽  
Austenitic Transformation ◽  
Heating And Cooling ◽  
Recovery Strain ◽  
High Annealing ◽  
Memory Characteristics

The present research aims to understand the transformation temperatures and recovery strain of NiTi wires during heating and cooling under various constrained stresses. Both constrained stress and annealing temperature have significant effects on the shape memory characteristics. In general, increasing constrained stress causes an increase of the austenitic and martensitic transformation temperatures and a decrease of the recovery strain. This effect can be attributed to that the constrained stress inhibits the austenitic transformation, and thus more volume fraction of the martensite is retained during heating. The high annealing temperature leads to the decrease in the recovery strain.

Martensitic Transformation and Shape Memory Effect in Titanium-Gold Compound

2011 ◽  
Vol 172-174 ◽  
pp. 49-54 ◽  
Author(s):  
Charles Declairieux ◽  
Philippe Vermaut ◽  
Richard Portier ◽  
Patrick Ochin ◽  
Anne Denquin
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Niti Alloy ◽  
Transformation Strain ◽  
Gold Compound ◽  
Compression Tests ◽  
Recoverable Strain ◽  
Ternary Element

High temperature shape memory alloys offer numerous potential applications in industrial domains like aeronautics. Even if up to now, none of the studied alloys have found a place in airplane turbines, research in this field is still active. Starting from the well-known “room temperature” shape memory alloy NiTi, it has been demonstrated that the addition of a ternary element such as gold in substitution of nickel greatly enhances the temperatures of the martensitic transformation. In the binary TiAu compound, the martensite start temperature can attain 875 K with satisfying reversibility and cycling stability. From lattice parameters measurements, it has been shown that the maximum transformation strain can reach 10.75 % for Ti47Au53alloy, which is comparable to that of the NiTi alloy. However, to the best of our knowledge, quantitative measurements of the recoverable strain by shape memory effect are not available in the literature. We present here some quantitative results of shape memory effect associated to this phase transformation in Titanium-Gold alloys measured after compression tests.

scholarly journals Microstructure, Mechanical Properties, and Martensitic Transformation in NiTi Shape Memory Alloy Fabricated Using Electron Beam Additive Manufacturing Technique

2021 ◽  
Author(s):  
Jan Dutkiewicz ◽  
Łukasz Rogal ◽  
Damian Kalita ◽  
Jakub Kawałko ◽  
Marek Stanisław Węglowski ◽  
...  
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Martensitic Transformation ◽  
Electron Beam Welding ◽  
Niti Shape Memory Alloy ◽  
Type I ◽  
Tensile Direction ◽  
Recoverable Strain ◽  
Deposition Direction

AbstractThe electron beam additive manufacturing (EBAM) method was applied in order to fabricate rectangular-shaped NiTi component. The process was performed using an electron beam welding system using wire feeder inside the vacuum chamber. NiTi wire containing 50.97 at.% Ni and showing martensitic transformation near room temperature was used. It allowed to obtain a good quality material consisting of columnar grains elongated into the built direction growing directly from the NiTi substrate, which is related to the epitaxial grain growth mechanism. As manufactured material showed martensitic and reverse transformations diffused over the temperature range from −10 to 44 °C, the applied aging at 500° C moved the transformation to higher temperatures and transformation peaks became sharper. The highest recoverable strain of about 3.5% was obtained in the as-deposited sample deformed along the deposition direction. In the case of deformation of the alloy aged at 500 °C for 2h, the formation of martensite occurs at significantly lower stress; however, at about 2.5% the stress begins to increase gradually and only a small shape recovery was observed due to a higher martensitic transformation temperature. In situ SEM tensile deformation in the direction perpendicular to deposition direction showed that the martensite began to appear at the surface of the sample and at the grain boundaries due to heterogeneous nucleation. In situ studies allowed to determine the following crystallographic relationships between B2 and B19’ martensite: (100)B2||(100)B19’ and (100) B2 || (011)B19’; (011)B2|| (001)B19’ and $${(011)}_{\mathrm{B}2}||{\left(11\bar{1 }\right)}_{\mathrm{B}1{9}^{\mathrm{^{\prime}}}}$$ ( 011 ) B 2 | | 11 1 ¯ B 1 9 ′ . Samples aged at 500 °C exhibited fully austenitic microstructure; however, with increasing degree of deformation, the formation of martensite was observed. The majority of needles were tilted about 45° with respect to the tensile direction, and the presence of type I (11 $$\bar{1 }$$ 1 ¯ ) invariant twin boundaries was observed at higher degrees of deformation.

scholarly journals Geometry and Distortion Prediction of Multiple Layers for Wire Arc Additive Manufacturing with Artificial Neural Networks

2021 ◽  
Vol 11 (10) ◽  
pp. 4694
Author(s):  
Christian Wacker ◽  
Markus Köhler ◽  
Martin David ◽  
Franziska Aschersleben ◽  
Felix Gabriel ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Welding Process ◽  
High Energy ◽  
Welding Distortion ◽  
Direct Energy Deposition ◽  
Direct Energy ◽  
Industrial Use ◽  
Artificial Neural ◽  
Artificial Neural Network Ann ◽  
Wire Arc Additive Manufacturing

Wire arc additive manufacturing (WAAM) is a direct energy deposition (DED) process with high deposition rates, but deformation and distortion can occur due to the high energy input and resulting strains. Despite great efforts, the prediction of distortion and resulting geometry in additive manufacturing processes using WAAM remains challenging. In this work, an artificial neural network (ANN) is established to predict welding distortion and geometric accuracy for multilayer WAAM structures. For demonstration purposes, the ANN creation process is presented on a smaller scale for multilayer beads on plate welds on a thin substrate sheet. Multiple concepts for the creation of ANNs and the handling of outliers are developed, implemented, and compared. Good results have been achieved by applying an enhanced ANN using deformation and geometry from the previously deposited layer. With further adaptions to this method, a prediction of additive welded structures, geometries, and shapes in defined segments is conceivable, which would enable a multitude of applications for ANNs in the WAAM-Process, especially for applications closer to industrial use cases. It would be feasible to use them as preparatory measures for multi-segmented structures as well as an application during the welding process to continuously adapt parameters for a higher resulting component quality.

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