The Segregation of Chemical Composition in NiTi Shape Memory Alloy Melted by VIM in Lime Crucible

2009 ◽  
Vol 610-613 ◽  
pp. 1315-1318 ◽  
Author(s):  
Zhi Shan Yuan ◽  
Zhao Wei Feng ◽  
Jiang Bo Wang ◽  
Wei Dong Miao ◽  
Chong Jian Li ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Large Scale ◽  
Vacuum Induction Melting ◽  
Niti Shape Memory Alloy ◽  
Induction Melting ◽  
Ingot Metallurgy ◽  
Chemical Homogeneity ◽  
Section Area

Binary NiTi shape memory alloy cast ingots with large scale size are produced by using vacuum induction melting (VIM) in lime crucible, the oxygen and carbon contents are less than 500ppm. Usually, oxygen was introduced into the melts by the dissolution of lime during melting, resulting in higher content of oxygen over 500ppm. VAR + VIM ingot metallurgy is prone to produce materials with a good chemical homogeneity. However, it is difficult for one single melting of NiTi by VIM in the lime crucible. So in the present paper, the segregation of chemical composition and the consistency of transformation temperature in NiTi alloys in as-casted condition along the cross-section area on edge and center, in homogeneization-treated condition, and in as-forged condition along the longitudinal-section area on head and tail, are measured and analyzed by differential scanning calorimetry (DSC), OM, SEM, and XRD, to indicate the chemical homogeneity in microscopic and macroscopic scale.

Influence of Heat Treatments on a NiTi Shape Memory Alloy Obtained Using Vacuum Induction Melting and Reprocessed by Plasma Skull Push-Pull

2015 ◽  
Vol 1765 ◽  
pp. 121-126 ◽  
Author(s):  
Jackson de Brito Simões ◽  
Francisco Fernando Roberto Pereira ◽  
Jorge Otubo ◽  
Carlos José de Araújo
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Electrical Resistance ◽  
Heat Treatments ◽  
Vacuum Induction Melting ◽  
Niti Shape Memory Alloy ◽  
Induction Melting ◽  
Thermal Treatments ◽  
Scanning Calorimetry ◽  
Thermally Induced

ABSTRACTShape memory alloys (SMA) are metallic attractive engineering materials due to their capacity to store pre-defined shapes through a thermally induced phase transition from a solid state. This paper aims to evaluate the influence of solubilization thermal treatments on a NiTi shape memory alloy originally fabricated by vacuum induction melting and then reprocessed by plasma melting followed by injection molding (Plasma Skull Push Pull process) into different metal molds (steel, aluminum, brass and copper) in order to compare the thermal properties regarding to its raw state. The thermal treatments of solubilization were carried out at 850°C in different times (2n function, n = 0, 1, 2 and 3, in hours). The influence of solubilizing treatments in the NiTi shape memory alloy was analyzed using the following characterization techniques: Differential Scanning Calorimetry (DSC) and Electrical Resistance as a function of Temperature (ERT). The results demonstrate that the solubilization heat treatments applied on the reprocessed NiTi shape memory alloy through the plasma skull push pull process, provides important changes in the phase transformation of the material. Therefore, it was demonstrated that it is necessary to solubilize the material after melting or remelting the NiTi shape memory alloy via this process to obtain mini-actuators products with homogeneous properties.

scholarly journals Effect of Sn Addition on Phase Transformation Behavior of Equiatomic Ni-Ti Shape Memory Alloy

2020 ◽  
Vol 17 (3(Suppl.)) ◽  
pp. 0961
Author(s):  
Ali Abadi Aljubouri ◽  
Safa hasan Mohammed ◽  
Mudhafar ali Mohammed
Keyword(s):  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Optical Microscope ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Micro Hardness ◽  
Transformation Behavior ◽  
Scanning Calorimetry ◽  
Phase Transformation Behavior

Sn effect on the phase transformation behavior, microstructure, and micro hardness of equiatomic Ni-Ti shape memory alloy was studied. NiTi and NiTiSn alloys were produced using vacuum induction melting process with alloys composition (50% at. Ni, 50% at.Ti) and (Ni 48% at., Ti 50% at., Sn 2% at.). The characteristics of both alloys were investigated by utilizing Differential Scanning Calorimetry, X- ray Diffraction Analysis, Scanning Electron Microscope, optical microscope and vicker's micro hardness test. The results showed that adding Sn element leads to decrease the phase transformation temperatures evidently. Both alloy samples contain NiTi matrix phase and Ti2Ni secondary phase, but the Ti2Ni phase content decreases with Sn addition and this is one of the reasons that leads to decrease the micro hardness of alloy with adding Sn element in a noticeable manner. The micro hardness decreases from 238.74 for NiTi equiatomic alloy to 202 for NiTiSn alloy after heat treatment.

Characterization of 150mm in Diameter NiTi SMA Ingot Produced by Electron Beam Melting

2010 ◽  
Vol 643 ◽  
pp. 55-59 ◽  
Author(s):  
Jorge Otubo ◽  
André da Silva Antunes
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Large Scale ◽  
Small Variation ◽  
Martensitic Transformations ◽  
Vacuum Induction Melting ◽  
Niti Shape Memory Alloy ◽  
Induction Melting ◽  
Composition Control

Earlier works showed that NiTi shape memory alloy production by electron beam melting (EBM) is a viable process in which its main characteristic is the low contamination by impurities such as carbon and oxygen. Some difficulties arise when compared to conventional vacuum induction melting (VIM) process such as composition control and complex machine operation. This work focus on the production of ever made large scale 150mm in diameter NiTi ingot produced by EBM showing its viability. The carbon contamination was only 0.016wt% compared to usual 0.05wt% of VIM process. The ingot radial composition homogeneity was proved by small variation presented by direct and reverse peak martensitic transformations temperatures which was around 2°C.

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