Lattice Defects of Cold-drawn and Aged Fe-36wt%Ni Alloys and Effects of Additions of C and V on Hardness and Thermal Expansion

Abstract

緒言Fe ・杉田 一樹2) ・井上 耕治3) ・白井 泰治2)Lattice Defects of Cold-drawn and Aged Fe-36wt%Ni Alloys and Effects of Additions of C and V on Hardness and Thermal ExpansionKazuo Nakama, Shinichi Furuya, Kazuki Sugita, Koji iNoue and Yasuharu Shirai Synopsis : Fe-36wt%Ni invar alloy has been widely used for precision parts where dimensional changes with temperature are unfavorable. In the viewpoint of industrial application, high-strength with low-thermal-expansion alloys are in increased demand for structural members such as power cables and electronic devices. Additions of alloying elements to and cold working on Fe-Ni alloys are effective methods that enable the alloys to strengthen, although these modifications also influence the magnitude of thermal expansion. In this study, effects of additions of 0.2wt%C and/or 0.8wt%V on hardness and thermal expansion of cold-drawn and aged Fe-36wt%Ni invar alloys are reported. Hardness in solution-treated and as-drawn conditions increased with addition of C, and, when both C and V were added, hardness of the alloy reached its maximum after aged at 650 ºC. Besides an increase in hardness with addition of any of C and V, thermal expansion below Tc became smaller in as-drawn condition than in solution-treated condition. Measurements of positron lifetimes revealed that vacancies introduced by cold-drawing were annealed out through aging up to 300 ºC and dislocation motion was activated at 500 ºC. Both vacancies and dislocations, especially C-dislocation complexes, seemingly influence the decrease in thermal expansion. While graphite precipitation in the C-added invar alloy showed no hardening, addition of C and V to invar alloy resulted in secondary hardening by vanadium carbide precipitation when aged over 500 ºC, which realized high-hardness and low-thermal-expansion. Key words : invar; thermal expansion; hardness; cold-drawing; aging; positron lifetime.平成 24 年 9月27日受付 平成 25 年 1月15日受理

Electrodeposition of Invar Fe-Ni Alloy/SiC Particle Composite

“…The influence of heat treatment at 600°C on hardness, linear expansion coefficient, and microstructure of the electrodeposited Fe-Ni alloy/SiC composite films Figure 2 shows the effect of heat treatment at 600°C on the hardness of the electrodeposited Invar Fe-Ni alloy/SiC composite films with various concentrations of co-deposited SiC. As reported previously (12,14), the hardness of the electrodeposited Invar Fe-Ni alloy films without co-deposited SiC decreases from 230 HV to 140 HV after heat treatment at 600°C; the heat-treated films exhibit approximately the same level of hardness as a pyrometallurgically produced Invar alloy (approximately 120 HV (20)).…”

Effect of aging on microstructures and properties of Mo-alloyed Fe–36Ni invar alloy

“…VC, NbC and Mo 2 C [13,14,20]. Nakama et al [13] reported that the invar alloy through precipitation of VC and TiC particles in the austenite matrix, together with subsequent 50% cold deformation presented the highest tensile strength of 1100 MPa, which is two times larger than that of the base Fe-36Ni alloy. Meanwhile, this alloy shows a low CTE value of 3 Â 10 À 6 /°C in the temperature range of 30-150°C.…”

“…Conventional strengthening methods, such as solid-solution strengthening [10], grain refinement [5], work hardening [8,11] and precipitation hardening [12][13][14][15][16], have been developed in invar alloys, e.g. Fe-36Ni [5,11], Fe-Ni-Co [12,17,18], Fe-Ni-Ti [19] and Fe-Ni-Mo [10,16], etc.…”

Fe–Ni Invar alloy reinforced by WC nanoparticles with high strength and low thermal expansion

“…The strengthening of Invar alloy can be achieved primarily through three methods: grain refinement [5], plastic deformation (and severe plastic deformation, SPD) [6], and precipitation hardening [4,[7][8][9]. Vingradov et al [8] reported that the tensile strength of Fe-36Ni Invar alloy can be increased to 912 MPa by refining the grain size to 180 nm using equal channel angular pressing (ECAP).…”

“…The strengthening of Invar alloy through the precipitation of MC-type carbides, such as TiC, VC, and Mo 2 C, or intermetallics, such as γ'-type Ni 3 Ti and Ni 3 Al, was reported to be highly effective. Nakama et al reported a Fe-Ni-V-C Invar alloy reaches a tensile strength of 1000 MPa after a combination of solutionization, aging, which produces VC precipitates, and cold working [7,9]; the same author reported the strengthening of Invar alloy containing Ti, V, and C through TiC and VC precipitation, and achieved 1100 MPa tensile strength at peak aging condition [6]. Yahagi et al reported a Fe-Ni-Co-Ti Invar alloy strengthened by the precipitation of γ'-type Ni 3 Ti intermetallics exhibits a tensile strength of 1313 MPa after cold working [10].…”