scholarly journals The Influence of the Soaking Temperature Rotary Forging and Solution Heat Treatment on the Structural and Mechanical Behavior in Ni-Rich NiTi Alloy

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 63
Author(s):  
Patrícia Freitas Rodrigues ◽  
Ronaldo S. Teixeira ◽  
Naiara V. Le Sénéchal ◽  
Francisco Manuel Braz Fernandes ◽  
Andersan S. Paula
Keyword(s):  
Heat Treatment ◽  
Solution Heat Treatment ◽  
Thermomechanical Processing ◽  
Niti Alloy ◽  
Structural Characteristics ◽  
Hot Forging ◽  
Scanning Calorimetry ◽  
Forging Process ◽  
Rotary Forging ◽  
Precipitate Dissolution

The structural and thermophysical characteristics of an Ni-rich NiTi alloy rod produced on a laboratory scale was studied. The soak temperature of the solution heat-treatment steps above 850 °C taking advantage of the precipitate dissolution to provide a matrix homogenization, but it takes many hours (24 to 48) when used without thermomechanical steps. Therefore, the suitable reheating to apply between the forging process steps is very important, because the product’s structural characteristics are dependent on the thermomechanical processing history, and the time required to expose the material to high temperatures during the processing is reduced. The structural characteristics were investigated after solution heat treatment at 900 °C and 950 °C for 120 min, and these heat treatments were compared with as-forged sample structural characteristics (one hot deformation step after 800 °C for a 30 min reheat stage). The phase-transformation temperatures were analyzed through differential scanning calorimetry (DSC), and the structural characterization was performed through synchrotron radiation-based X-ray diffraction (SR-XRD) at room temperature. It was observed that the solution heat treatment at 950 °C/120 min presents a lower martensitic reversion finish temperature (Af); the matrix was fully austenitic; and it had a hardness of about 226 HV. Thus, this condition is the most suitable for the reheating stages between the hot forging-process steps to be applied to this alloy to produce materials that can display a superelasticity effect, for applications such as crack sensors or orthodontic archwires.

scholarly journals Microstructural characterization of NiTi shape memory alloy produced by rotary hot forging

2017 ◽  
Vol 32 (S1) ◽  
pp. S201-S206
Author(s):  
P. Rodrigues ◽  
F. M. Braz Fernandes ◽  
A. S. Paula ◽  
J. P. Oliveira ◽  
S. B. Ribeiro ◽  
...  
Keyword(s):  
Shape Memory ◽  
Thermomechanical Processing ◽  
Niti Alloy ◽  
Cold Deformation ◽  
Hot Forging ◽  
Microstructural Characterization ◽  
Niti Shape Memory Alloy ◽  
Scanning Calorimetry ◽  
Rotary Forging

The thermomechanical processing of NiTi shape memory alloys usually involves several steps of hot and/or cold deformation. The present work presents the structural characterization of a Ni-rich NiTi alloy bar, produced by vacuum-induced melting and thermomechanical processing in laboratory scale, aiming at massive production in the future. This study focused on the first step of hot working at 800 °C during rotary forging. Microstructural characterization was performed using differential scanning calorimetry, high- and low-temperature X-ray diffraction (XRD) using a laboratory source and synchrotron XRD. Thus, it was possible to obtain the phase transformation characteristics of the material: the transformation temperatures and the transformation sequence. Proposed thermomechanical processing is intended for production of bars and wires that will be subsequently drawn to get thin wires, for different applications, including orthodontic arch wires.

scholarly journals The influence of aging treatment on the microstructural and mechanical behavior by ultra-micro hardness tester in Ni-rich NiTi alloy

2021 ◽  
Vol 16 (47) ◽  
Author(s):  
Naiara Vieira Le Sénéchal ◽  
Rodolfo Teixeira ◽  
Patrícia Freitas Rodrigues ◽  
Shimeni Baptista Ribeiro ◽  
Andersan dos Santos Paula
Keyword(s):  
Heat Treatment ◽  
Mechanical Behavior ◽  
Solution Heat Treatment ◽  
Niti Alloy ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Micro Hardness ◽  
Thermomechanical Process ◽  
Rotary Forging ◽  
Cold Rotary Forging

The present study aims to assess the superelasticity behavior in Ni-rich NiTi alloy wire produced by rotary forging process. The thermomechanical process involved four steps of hot working at 800ºC, two steps of cold working with solution heat treatment at 800ºC between them, and subsequently a solution heat treatment (950ºC during 2 hours) followed by aging treatment at 350, 400 and 450 ºC during 30 minutes. X-ray diffraction (XRD) and instrumented ultra-micro hardness testers evaluated the present phase at each aged sample and were compared with their mechanical behavior. The results put in evidence the work-hardening effect on a forged condition associated with the final step of cold rotary forging. The solution treatment promotes stress relaxation and precipitate dissolution. The sample heat-treated shows the presence of the precipitated (Ni4Ti3) and R phase. The presence of these precipitates is beneficial because precipitation-hardening increases the yield strength of austenite, which in turn contributes to better functional stability.

Preform and Die Designs for Hot Forging Process of Linear Slide Block

2013 ◽  
Vol 419 ◽  
pp. 395-400 ◽  
Author(s):  
Cheng Hsien Yu ◽  
Jinn Jong Sheu
Keyword(s):  
Heat Treatment ◽  
Hot Forging ◽  
Laser Heat Treatment ◽  
Forging Process ◽  
Die Filling ◽  
Slide Block ◽  
Laser Heat ◽  
Wear And Corrosion ◽  
Linear Slide ◽  
Hot Forging Process

In this study, the preform and die designs of hot forging process were proposed for a long-flat slide block. This block is assembled to the linear slide for carrying the moving table. Three different billet geometry designs were proposed to obtain good die filling. The volume of the flash is limited to 30% with a flash thickness design in 3 mm. The forging die was designed with four ejectors to push up the forged part smoothly. The proposed billet geometries and die design were evaluated using CAE simulation. The simulation results indicated that the suitable perform design is able to achieve better material flow. The flash flow control is able to reduce the forming load and improve the die filling. The forging experiments were carried out to verify the proposed method, the experiment results showed good agreement with the CAE simulations. For the Improvement of wear and corrosion resistances of Inconel718 (In718) surface, high velocity oxygen fuel (HVOF) thermal spray coating of micron-sized WC-Cr-C-Ni powder was coated onto Inconel718 surface and laser heat-treatment of the coating was carried out. Porous coating of porosity 2.2±0.4% was prepared by HVOF coating, and it was improved by laser heat-treatment, reducing the porosity to 0.35±0.08%. Micro-hardness of laser heat-treated coating increased more than four times compared to the surface of In718. Friction coefficient decreased by HVOF coating and laser heat-treatment. Wear resistance improved, decreasing the wear depth by the coating and laser heating. The interface between coating and In718 was compacted, and elements diffused from both coating and inconel718 substrate to interface, forming metal rich buffer zone (interface) and enhancing the adhesion of coating. Corrosion resistance improved by coating in sea water 3.5% NaCl solution and in 1M HCl acid, but it worsened in 1M NaOH base. For the improvement of wear and corrosion resistances of Inconel718, HVOF WC-metal power coating and laser heat-treatment are recommended.

Optimization of the Solution Heat Treatment of Rheo-High Pressure Die Cast Al-Cu-Mg-Ag 2139 Alloy

2015 ◽  
Vol 828-829 ◽  
pp. 226-231 ◽  
Author(s):  
Pfarelo Daswa ◽  
Heinrich Möller ◽  
Gonasagren Govender
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Aluminium Alloy ◽  
Solution Heat Treatment ◽  
Volume Fraction ◽  
High Volume ◽  
Single Step ◽  
Incipient Melting ◽  
Scanning Calorimetry ◽  
Die Cast

This paper investigates the optimization of the solution heat treatment parameters of the rheo-high pressure die cast (R-HPDC) 2139 aluminium alloy. Differential Scanning Calorimetry (DSC) and optical microscopy were used to investigate the incidence of incipient melting and therefore determine suitable solution heat treatment temperatures. A three-step solution heat treatment where the alloy was heat treated from 400°C to 513°C using controlled heating conditions and held at 513°C for 2 hours and finally heated up from 513°C to 525°C and held there for 16 hours was done. R-HPDC is known to produce surface liquid segregation and when processing the alloys these areas are most prone to incipient melting. The applicability of a single (525°C for 16h) and three-step solution heat treatments on the R-HPDC 2139 aluminium alloy was also investigated. A single-step solution heat treatment results in incipient melting, whereas this is mostly eliminated using the three-step solution heat treatment. However, a high volume fraction of undissolved phases remain in the liquid segregated areas, even after the three-step solution heat treatment.

Heat Treatment Variability Effects on the Mechanical Properties of Beta Solution Treated Ti-6Al-4V

2010 ◽  
Vol 638-642 ◽  
pp. 401-406
Author(s):  
J.R. Calcaterra
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Fracture Toughness ◽  
Solution Heat Treatment ◽  
Thermomechanical Processing ◽  
Tensile Tests ◽  
Maximum Temperature ◽  
Work Piece ◽  
Fatigue Crack Growth Resistance ◽  
Heat Treated

Beta solution heat treatment is used to increase the fatigue crack growth resistance of Ti-6AL-4V. Unfortunately, the beta solution heat treatment is very sensitive to maximum temperature, time at temperature and cooling rate. In order to determine the effect of these parameters on mechanical properties, several different titanium billets and forgings were heat treated at various times and temperatures. The forgings had differing amounts of work, reflecting the potential for thermomechanical processing differences seen in a die forged component. Fracture toughness and tensile tests were conducted on the billets and forgings. In addition, sections of each work piece were excised and examined microscopically. The results from the study indicate there is a significant effect of heat treatment on thicker section components. In these cases, grains near the surface may grow large, while being barely transformed near the center. The change in microstructure has an effect on mechanical properties. Material with the larger grains tends to have worse ductility, while the fracture toughness properties of the material tend to decrease with grain size.

The Solution Heat Treatment of Rheo-High Pressure Die Cast Al-Mg-Si-(Cu) 6xxx Series Alloys

2014 ◽  
Vol 217-218 ◽  
pp. 259-264 ◽  
Author(s):  
Pfarelo Daswa ◽  
Heinrich Möller ◽  
Madeleine du Toit ◽  
Gonasagren Govender
Keyword(s):  
Heat Treatment ◽  
High Pressure ◽  
Aluminium Alloys ◽  
Solution Heat Treatment ◽  
High Strength ◽  
Incipient Melting ◽  
Scanning Calorimetry ◽  
Die Cast ◽  
Liquid Segregation ◽  
6Xxx Series

The 6xxx series alloys are well known for desirable combinations of high strength, weldability, corrosion resistance and formability. This paper investigates the influence of chemical composition on the solution heat treatment parameters of rheo-high pressure die cast (R-HPDC) 6xxx series aluminium alloys. The presence of copper in the 6xxx series aluminium alloys affects the solution heat treatment by promoting incipient melting. The incidence of incipient melting is investigated for the R-HPDC alloys using Differential Scanning Calorimetry (DSC) and optical microscopy. R-HPDC is known to produce surface liquid segregation and centre-line liquid segregation when processing the alloys and these areas are the most susceptible to incipient melting. The applicability of single and multiple step solution heat treatments are investigated. The alloys used for this study include the Cu-free alloy 6082, as well as the Cu-containing alloys 6013 and 6111.

scholarly journals In-Situ Analysis Of Incipient Melting And Characterization Of A Novel Al-Cu Alloy for Cylinder Head Applications

2021 ◽  
Author(s):  
Bernoulli Andilab
Keyword(s):  
Heat Treatment ◽  
Solution Heat Treatment ◽  
Laser Scanning ◽  
Microstructural Analysis ◽  
Secondary Phases ◽  
Incipient Melting ◽  
Scanning Calorimetry ◽  
Slow Cooling ◽  
Cu Alloy

Incipient melting of secondary phases during solution heat treatment of Al alloys is detrimental to their mechanical properties. In this research, incipient melting was analyzed in-situ using a high temperature Laser Scanning Confocal Microscope (LSCM) in a novel Al-Cu alloy. Thermal analysis and microstructural analysis were carried out on the alloy cast at fast and slow cooling rates to examine the resulting solidification and microstructural characteristics. The results showed that incipient melting was accompanied by a clustering liquid droplets followed by a complete melting of Al2Cu which occurred at approximately 548 ℃. Additionally, the use of LSCM enabled an understanding of the underlying mechanisms behind incipient melting. It was also found that incipient melting led to microstructure that consisted of a higher presence of ultra-fine eutectic clusters, needle-like Al2Cu and porosity along the grain boundaries. Lastly, the solution heat treatment temperature was optimized for the Al-Cu alloy using the data from LSCM, Differential Scanning Calorimetry and solution heat treatment experiments.

INFLUENCES OF HEAT TREATMENT ON TRANSFORMATION BEHAVIORS OF NEAR-EQUIATOMIC POROUS NITI SHAPE MEMORY ALLOY

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2410-2416
Author(s):  
H. C. JIANG ◽  
Y. CHEN ◽  
S. W. LIU ◽  
L. J. RONG
Keyword(s):  
Heat Treatment ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Alloy ◽  
Niti Shape Memory Alloy ◽  
Scanning Calorimetry ◽  
Pore Characteristics ◽  
Transformation Temperatures ◽  
Porous Niti ◽  
High Temperature Synthesis

The pore characteristics and pore size distribution of porous near-equiatomic NiTi shape memory alloy fabricated by self-propagating high-temperature synthesis (SHS) are described in detail. The effects of different heat treatments on the transformation of porous NiTi alloy were investigated by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that heat treatment had strong influences on the transformation temperatures and latent heats of transformation. When the porous alloy was annealed at 648K and 748K for 3.6ks, two steps transformation including R transformation occurred during cooling and heating and the R transformation temperatures are lower than B 2↔ B 19' transformation temperatures. However, no transformation was detected within the experimental temperature range if the porous alloy was solution treated at 1133K for 2.4ks. This novel phenomenon was the results of extensive Ti2Ni intermetallic compound precipitation. The transformation temperatures of porous NiTi alloy after annealing at 1323K for 3.6ks were much lower than those of the untreated alloy.

scholarly journals Modeling of Isothermal Dissolution of Precipitates in a 6061 Aluminum Alloy Sheet during Solution Heat Treatment

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1234
Author(s):  
Yong Liu ◽  
Dongyu Fang ◽  
Bin Zhu ◽  
Yilin Wang ◽  
Shiqi Li ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloy ◽  
Solution Heat Treatment ◽  
Alloy Sheet ◽  
Dissolution Time ◽  
Mobile Nodes ◽  
6061 Aluminum Alloy ◽  
Precipitate Dissolution ◽  
Time Modeling ◽  
Dissolution Model

During the solution heat treatment (SHT) process of aluminum alloys, precipitates dissolve into the matrix. To predict the dissolution time, modeling of isothermal dissolution of precipitates in 6061 aluminum alloy during SHT was conducted. A precipitate dissolution model was established, and the flowchart of the modeling was designed as well. Then the explicit finite-difference method was employed to solve the dissolution model, and the mobile nodes method was used to deal with the moving interface. The simulation was based on real precipitates in 6061, and SHT experiments were conducted to validate the numerical model. The simulation results showed that the isothermal dissolution time of precipitates in 6061-T6 aluminum alloy at 560 °C is 11.6856 s. The dissolution time in the simulation was close to the experimental results, with an error of 16.7%, indicating that the modeling in this study was fairly reasonable and accurate. The error was caused by many factors, and the model should be improved.

scholarly journals In-Situ Analysis Of Incipient Melting And Characterization Of A Novel Al-Cu Alloy for Cylinder Head Applications

2021 ◽  
Author(s):  
Bernoulli Andilab
Keyword(s):  
Heat Treatment ◽  
Solution Heat Treatment ◽  
Laser Scanning ◽  
Microstructural Analysis ◽  
Secondary Phases ◽  
Incipient Melting ◽  
Scanning Calorimetry ◽  
Slow Cooling ◽  
Cu Alloy

Incipient melting of secondary phases during solution heat treatment of Al alloys is detrimental to their mechanical properties. In this research, incipient melting was analyzed in-situ using a high temperature Laser Scanning Confocal Microscope (LSCM) in a novel Al-Cu alloy. Thermal analysis and microstructural analysis were carried out on the alloy cast at fast and slow cooling rates to examine the resulting solidification and microstructural characteristics. The results showed that incipient melting was accompanied by a clustering liquid droplets followed by a complete melting of Al2Cu which occurred at approximately 548 ℃. Additionally, the use of LSCM enabled an understanding of the underlying mechanisms behind incipient melting. It was also found that incipient melting led to microstructure that consisted of a higher presence of ultra-fine eutectic clusters, needle-like Al2Cu and porosity along the grain boundaries. Lastly, the solution heat treatment temperature was optimized for the Al-Cu alloy using the data from LSCM, Differential Scanning Calorimetry and solution heat treatment experiments.

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