Investigation of structural, elastic and magnetic properties of Fe65Ni35 and Fe70Ni30 alloys doped with interstitial elements

This study is about how the mechanical, magnetic, and structural properties of Invar alloys change with the addition of interstitial carbon (C) elements. Structural changes of Fe65Ni35 and Fe70Ni30 alloys prepared by melting method in arc furnace were investigated in terms of structural, magnetic and elastic properties. The structural changes were observed with an x-ray diffractometer (XRD). Elastic modulus measurements were performed with impulse excitation technique (IET) device and magnetic properties were measured with a superconducting quantum interference device (SQUID). As a result of the measurements, the addition of the interstitial element caused different effects for two different Invar alloy series. Based on the XRD results, it was concluded that Fe65Ni35 Invar alloy remains as FCC crystal structure within the range of C addition. According to the elastic modulus results for Fe65Ni35, the temperature region corresponding to the Invar property observed shifts near to the room temperature by increasing carbon ratio. From the magnetization results, it was also concluded that the Curie temperatures decrease with increasing C content. In contrast, while the Fe70Ni30 Invar alloy exhibits both BCC and FCC structures together, the BCC structure disappears with increasing amounts of C. According to the elastic modulus results, the Invar property region expands in a larger temperature range by shifting to the higher temperatures with increasing C amount. It was similarly concluded that the Curie temperatures increase with increasing C amount. According to the obtained results, the valence electron numbers and magnetic moment values are evaluated and results interpreted in view of the Slater-Pauling rule for these two Invar systems.