Effect of carbon on the coefficient of thermal expansion of as-cast Fe−30wt.%Ni−12.5wt.%Co−×C invar alloys

Abstract

The segregation (distribution) of nickel and the composition of its constituents influence the low thermal expansion characteristics (Invar effect) in Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy. The change of coefficient of the thermal expansion and magnetic properties were studied as an aspect of carbon addition causing the segregation of Ni in primary austenite of as-cast Fe-30 wt.% Ni-12.5 wt.% Co Invar alloy. The coefficient of thermal expansion of Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy showed its lowest value at 0.08 wt.% carbon, increased with increasing carbon content in the range of 0.08-1.0 wt.%C, kept constant at 1.0-2.0 wt.%C and decreased at carbon higher than 2.0 wt.%. The effective distribution of the coefficient of nickel in as-cast Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy increased with increasing carbon content. The volume fraction of the γ phase of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy increased with increasing carbon content. The microstructure of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy changed with the carbon content was independent of the coefficient of thermal expansion. The Curie temperature changed linearly with the carbon content and was similar to the change of the coefficient of thermal expansion. Moreover, the coefficient of thermal expansion decreased when the ratio of saturation magnetization to Curie temperature (σ s /T c ) increased, decreasing the Curie temperature and showed a specific relationship with the magnetic properties of the Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy.

Synthesis of Pyrazole‐Based Pyridine Ligands and Their Use as Extractants for Nickel(II) and Copper(II): Crystal Structure of a Copper(II)–Ligand Complex

“…[1] By far, the majority of uses for nickel arise from its alloys, most notably stainless steel . However, other nickel‐containing alloys have special high‐end applications, such as a nickel alloy created by Kim and co‐workers that has a thermal expansion coefficient of zero. Miller and co‐workers, on the other hand, created a nickel–titanium alloy that displays shape‐memory characteristics.…”

Mechanical and functional properties of Invar alloy forμ-MIM

“…Heterogeneities in the cast alloy and the presence of other elements like carbon introduce the possibility of formation of Ni segregation regions within the c lattice. [11][12][13][14] Therefore, low moment paramagnetic Fe rich phases could coexist with clusters of Ni rich high moment ferromagnetic order phase negatively affecting CTE. Furthermore, a martensitic phase could be formed for quenched alloys, which also degrade low expansion properties.…”