Session: 04-11-03: Advanced Materials Processing and Property Characterization

Paper Number: 145198

145198 - Effect of Soaking Time on the Thermomechanical Response of Sintered Niti Shape Memory Alloy 

Shape memory alloys (SMAs) are a class of smart materials capable of recovering their pre-deformed shape when certain conditions are met. Due to their distinctive functional characteristics, shape memory alloys have garnered significant interest for their prospective usage in several technical fields, including stents, orthodontic wires, aerospace, and automotive sectors. Nickel-titanium (nitinol) is the most often used metal system for shape memory behavior. Nitinol components may be manufactured by the process of sintering compressed elemental or pre-alloyed metal powder. This technique requires the creation and utilization of a suitable mold. The standard sintering method typically entails compressing metal powder into the desired part shape to create a green part, which is subsequently exposed to proper heat treatment, leading to the sintering of nitinol. However, recent studies show that pressureless sintering of uncompacted pre-alloyed powder is a feasible method for fabricating nitinol. Using this technique omits the need to compress the powder into a green part prior to sintering. This study investigates the impact of soaking time on the production of nitinol by pressureless sintering of pre-alloyed NiTi shape memory alloy powder. The approach under consideration entails an initial preheating phase, followed by sintering at a suitable rate and for different adequate durations in a vacuum environment. The mechanical response of the generated samples is examined by uniaxial compression tests in order to assess the effectiveness of this production technique. The outcomes of these tests are compared with the typical observations made for nitinol samples produced using different methods. Moreover, the effect of the soaking time on the microstructure of the samples is assessed using electron backscattering diffraction (EBSD). Furthermore, the examination of the sintered samples' functional characteristics is conducted through various methods. These methods encompass macro hardness tests and subsequent heating to analyze their shape memory properties, X-ray diffraction and elemental mapping utilizing energy dispersive spectroscopy (EDS) to verify the composition of the material, and differential scanning calorimetry (DSC) to investigate the temperatures at which phase transformations occur. The DSC thermograms obtained in this regard demonstrate the existence of phase transformation peaks that are similar to those observed in the stock powder. The findings of this study demonstrate that the soaking time affects the final produced nitinol parts in different aspects of its performance. In addition, the microstructure of the fabricated parts is dependent on the thermal processing of the produced parts. Fabricating nitinol using this process remains a promising method for creating functional parts in a less complex process.

Presenting Author: Fares Alawwa Khalifa University

Presenting Author Biography: A PhD candidate in Khalifa University working on nitinol shape memory alloy

Authors:

Fares Alawwa Khalifa University
Rashid Abu Al-Rub Khalifa University
Bashar El-Khasawneh Khalifa University
Wael Zaki Khalifa University