Super Invar Research Articles

Phase Stability and Thermal Expansion Properties of Additive Manufactured Super Invar alloy

Phase Stability and Thermal Expansion Properties of Additive Manufactured Super Invar alloy

Strengthening of Super Invar Cast Steel by Precipitation of Intermetallic Compounds

Strengthening of Super Invar Cast Steel by Precipitation of Intermetallic Compounds

Simultaneous Optimization of Rigidity and Strength of Super Invar Cast Steel using by Martensitic Reversion

Simultaneous Optimization of Rigidity and Strength of Super Invar Cast Steel using by Martensitic Reversion

Combinatorial development of multicomponent Invar alloys via rapid alloy prototyping

To develop novel Invar alloys in the practically infinite compositional space of multicomponent alloys, rapid alloy prototyping is used to investigate five multicomponent Invar alloys with 5 at.% addition of Al, Cr, Cu, Mn and Si to a super Invar alloy (Fe63Ni32Co5; at.%), respectively. All alloys show abnormally low thermal expansion coefficients below the Curie temperature and saturation magnetization deviating from the Slater-Pauling curve, revealing their Invar-behavior. The relationships among valence electron concentration, magnetic properties, and Invar behavior of the various multicomponent alloys are discussed. The Invar alloy with Cu addition is particularly promising, as it shows a 40 K larger temperature range (above room temperature) of low thermal expansion coefficient (<5.87×10−6 K) and slightly higher hardness compared to the conventional super Invar alloy. The work thus also successfully demonstrates the capability of using rapid alloy prototyping for developing multicomponent multi-functional alloys.

Ultrawide Temperature Range Super-Invar Behavior of R_{2}(Fe,Co)_{17} Materials (R = Rare Earth).

Super Invar (SIV), i.e., zero thermal expansion of metallic materials underpinned by magnetic ordering, is of great practical merit for a wide range of high precision engineering. However, the relatively narrow temperature window of SIV in most materials restricts its potential applications in many critical fields. Here, we demonstrate the controlled design of thermal expansion in a family of R_{2}(Fe,Co)_{17} materials (R=rare Earth). We find that adjusting the Fe-Co content tunes the thermal expansion behavior and its optimization leads to a record-wide SIV with good cyclic stability from 3-461K, almost twice the range of currently known SIV. In situ neutron diffraction, Mössbauer spectra and first-principles calculations reveal the 3d bonding state transition of the Fe-sublattice favors extra lattice stress upon magnetic ordering. On the other hand, Co content induces a dramatic enhancement of the internal molecular field, which can be manipulated to achieve "ultrawide" SIV over broad temperature, composition and magnetic field windows. These findings pave the way for exploiting thermal-expansion-control engineering and related functional materials.

Manufacture of Narrow Thin-Walled Super Invar Pipe

The manufacture of thin-walled narrow pipe from 32NKD Super Invar alloy by drawing is studied. The drawing forces on the mandrel and the pipe blank are determined. The influence of the lubricant on the frictional forces is analyzed. The linear-expansion coefficient of the thin-walled pipe produced by drawing is compared with that of an undeformed sample of 32NKD alloy, as a function of the temperature.

Simultaneous Optimization of Rigidity and Strength of Super Invar Cast Steel using by Martensitic Reversion

Simultaneous Optimization of Rigidity and Strength of Super Invar Cast Steel using by Martensitic Reversion

Combinatorial Development of Multicomponent Invar Alloys Via Rapid Alloy Prototyping

To develop novel Invar alloys in the practically infinite compositional space of multicomponent alloys, rapid alloy prototyping is used to investigate five multicomponent Invar alloys with 5 at.% addition of Al, Cr, Cu, Mn and Si to a super Invar alloy (Fe 63 Ni 32 Co 5 ; at.%), respectively. All alloys show abnormally low thermal expansion coefficients below the Curie temperature and saturation magnetization deviating from the Slater-Pauling curve, revealing their Invar-behavior. The relationships among valence electron concentration, magnetic properties, and Invar behavior of the various multicomponent alloys are discussed. The Invar alloy with Cu addition is particularly promising, as it shows a 40 K larger temperature range (above room temperature) of low thermal expansion coefficient (<5.87×10 -6 K) and 2.8% higher hardness compared to the conventional super Invar alloy. The work thus also successfully demonstrates the capability of using rapid alloy prototyping for developing multicomponent multi-functional alloys.

Improvement of Rigidity of Super Invar Cast Steel via Austenite Recrystallization Induced by Martensitic Reversion

Improvement of Rigidity of Super Invar Cast Steel via Austenite Recrystallization Induced by Martensitic Reversion

Round robin comparison study on the form measurement of optical freeform surfaces

A round robin comparison of freeform form measurements was carried out by the project partners and stakeholders of a European metrology research project. Altogether six measuring instruments were considered: five different (pointwise and areal) optical devices and one tactile device. Three optical freeform surfaces were used for the comparison measurements, where two specimens were measured by five instruments and one specimen by four instruments. In this paper, the evaluation methods and results of this round robin are presented for the three freeform surfaces made from a temperature-stable material, Super Invar ®. The freeforms had diameters of 40 mm, 50 mm and 100 mm and best-fit radii of 39.75 mm (convex), 40.9 mm (convex) and 423.5 mm (concave). For comparison, the bilateral pointwise differences between the available measurements were calculated. The root-mean-square values of these differences ranged from 15 nm to 110 nm (neglecting spherical contributions) and provided an insight into the status of typical freeform measurement capabilities for optical surfaces.

Invar effects in FeNiCo medium entropy alloys: From an Invar treasure map to alloy design

To facilitate the understanding of Invar effects and design of FeNiCo-base Invar alloys characterized by low thermal expansion coefficient (TEC), we investigated the magnetic and thermal expansion behavior of an equiatomic prototype medium entropy alloy FeNiCo and a non-equiatomic (super Invar) Fe63Ni32Co5 (at. %) reference alloy by means of experiments and ab initio calculations. Both alloys consist of a single face-centered cubic phase with fully recrystallized microstructure in the homogenized state. Large spontaneous volume magnetostriction is observed in both alloys below their respective Curie temperatures. The Invar effect in the non-equiatomic Fe63Ni32Co5 alloy is of step-type with nearly zero TEC over a wide temperature range (from room temperature to 120 °C) below its Curie temperature. The equiatomic FeNiCo alloy shows a peak-type Invar effect in a very narrow temperature range (from ∼675 °C to ∼730 °C) with relatively low TECs. The equiatomic FeNiCo alloy shows both higher saturation magnetization and Curie temperature than the non-equiatomic Fe63Ni32Co5 alloy. The relationships among magnetic behavior, spontaneous volume magnetostriction and Invar effects for a wider array of metallic alloys are discussed mainly based on Masumoto's rule combined with Wohlfarth's itinerant electron theory. An Invar alloy search map is constructed based on the present results and available literature data to visualize the relationships among saturation magnetization, Curie temperature and thermal expansion coefficient for a wide range of Invar alloys. Based on this treasure map a design route for further developments of new Invar alloys by tuning their magnetic properties is discussed.

Improvement of Rigidity of Super Invar Cast Steel &lt;i&gt;via&lt;/i&gt; Austenite Recrystallization Induced by Martensitic Reversion

Improvement of Rigidity of Super Invar Cast Steel &lt;i&gt;via&lt;/i&gt; Austenite Recrystallization Induced by Martensitic Reversion

New Type Fe-Mn Based Alloys with Super Elinvar and Invar Characteristics

New Type Fe-Mn Based Alloys with Super Elinvar and Invar Characteristics

Template Fe-Ni-Co Nanowire Electrodeposition with H2 Evolving Side Reactions

Introduction Template-based electrodeposition is of interest for the fabrication of nanowires due to its low cost, ease of implementation, and for 1D dimensional control at the nanoscale. Two types of templates are commonly used: (1) polymer track etched membranes, and (2) porous alumina (AAO) membranes.1-2 There is a challenge in electrodepositing metals and alloys when the side reaction is appreciable, due to the generation of hydrogen gas bubbles, and the accompanying local pH change. One strategy to circumvent these problems is to apply a pulsating current or potential. Previous work in our lab showed successful deposition of Super Invar (64 wt% Fe, 31 wt% Ni, and 5 wt% Co) nanowires by using a pulse strategy.3 Disadvantages of pulsed techniques include the formation of layers with dissimilar composition, when a uniform composition is desired, and that the process is more time intensive. This research focusses on the use of direct current (DC) deposition with the membrane choice being a key factor when the hydrogen side reaction is substantial. Experimental Fe-Ni-Co nanowires were fabricated galvanostatically with a three-electrode cell. The electrolyte contained 0.72 M nickel sulfate, 0.155 M ferrous sulfate, 0.005 M cobalt sulfate, 0.5 M boric acid, 0.001 M sodium lauryl sulfate, 0.011 M ascorbic acid, at pH = 2 and the temperature of 40 °C with and without surfactants. Both AAO and polycarbonate (PC) membranes were used. A gold conductive film was sputtered on one side of membrane, serving as the cathode. The electrodeposition process was terminated when the nanowire reached the top of the membrane. Nanowires were removed from templates by being dissolved in dichloromethane (for PC) or 1 M NaOH solution (for AAO). The structures of nanowires were inspected by TEM (JEOL JEM-1010). Results and Discussion Figure 1 shows TEM images of nanowires in (a) AAO and (b) PC with DC current. Long, unbroken nanowires are observed in AAO while in contrast, fragmented nanowires are observed in PC membranes. An explanation for the different structures observed is based on the hydrogen permeability into the membrane materials. It is expected that inorganic membranes have a higher hydrogen permeability than polymeric membranes.4 The lower hydrogen permeability of PC membranes lead to higher hydrogen concentration inside the pore region of the membranes, creating a higher driving force for its permeability into the metal, and thus producing more fragile nanowires than in AAO. Conclusion Fabrication of FeNiCo nanowires in both AAO and PC membranes via DC electrodeposition was achieved. More robust nanowires are found with AAO due to differences in hydrogen permeability between AAO and PC. Acknowledgement The authors thank Roche Diagnostics for support of this project. The author also would like to thank Bill Fowle and Wentao Liang for microscopy help. Reference C. R. Martin, Science, 266 1961 (1994).A. Huczko, Appl. Phys. A. 70 365 (2000).H. Kim, M. C. Murphy, and E. J. Podlaha, J. Electrochem. Soc. 159 D549 (2012).G. Q. Lu, J. C. Diniz da Costa, M. Duke, S. Giessler, R. Socolow, R. H. Williams, T. Kreutz, J. Colloid Interface Sci. 314 589 (2007). Figure 1

Consideration of coordinated solar tracking of an array of compact solar-pumped lasers combined with photovoltaic cells for electricity generation

A monochromatic laser light with a photon energy just above the band edge of photovoltaic cells can be converted into electricity with minimal thermal loss. To attain efficient conversion of sunlight to laser light, a coordinated solar tracking system for an array of originally designed compact solar-pumped lasers of 50 mm aperture diameter is being constructed. As for the feasibility of this system, a prototype with a holding capacity of 25 compact solar-pumped lasers has been fabricated. The primary requisite of this system is that the angular accuracy of tracking should be below 1 mrad for all 25 compact solar-pumped lasers to sustain their continuous lasing. To realize this, imperative challenges have been elucidated including thermal expansion under sunlight. A prototype fabricated with its main frame made of Super Invar alloy was found to fulfill the requisite by measurement using a three-dimensional coordinate measuring machine.

Uncertainty evaluation of a 10N·m dead weight torque standard machine and comparison with a 1kN·m dead weight torque standard machine

A 10N·m dead weight torque standard machine (10-N·m-DWTSM) has been developed and evaluated since 2006 at the National Metrology Institute of Japan (NMIJ), a part of the National Institute of Advanced Industrial Science and Technology (AIST). Previously, the lengths of a moment arm, made of a low-thermal-expansion alloy (Super Invar), and the sensitivity limit of the fulcrum were evaluated. However, it is known that mechanical parts made of Super Invar vary in size with time. Therefore, the sensitivity limit of the fulcrum should be investigated under real calibration conditions. In this study, the moment arm lengths and the sensitivity limit of the fulcrum were re-evaluated. The moment arm lengths were found to have increased by an average of 6.3μm in five years. The relative combined standard uncertainty of the moment arm length, warm, was re-evaluated in consideration of the uncertainty of the secular length change and was found to be 1.8×10−5. The sensitivity limit of the fulcrum was investigated by using a highly accurate, small-rated-capacity torque measuring device. The relative combined standard uncertainty due to the sensitivity limit of the fulcrum was 2.5×10−5 in the 0.1–10N·m torque range. The uncertainty budget table of the 10-N·m-DWTSM was completed. The relative expanded uncertainty of torque realized by the 10-N·m-DWTSM, Wtsm, was evaluated in the 0.1–10N·m torque range and was found to be 6.6×10−5, with a coverage factor, k, being equal to 2. In addition, the 10-N·m-DWTSM was compared with the existing 1-kN·m-DWTSM at NMIJ by using small-rated-capacity torque measuring devices at 5N·m and 10N·m torque steps. Two loading conditions were adopted in this comparison. The comparison results showed good agreement within the uncertainties in all cases. Thus, the torque realized by the 10-N·m-DWTSM was shown to be equivalent to that achieved by the 1-kN·m-DWTSM.

Effect of substrate on the 3 body abrasion wear of HVOF WC-17 wt.% Co coatings

WC-17wt.% Co coatings were deposited using high velocity oxy-fuel (HVOF) spraying onto four different substrate materials, namely aluminium, brass, 304 stainless steel and super-invar. These substrates have different coefficients of thermal expansion which have been shown to influence the final coating microstructural properties. The abrasive wear properties of the coatings were characterised using an ASTM-G65 three body abrasive wear machine with silica sand as the abrasive. The highest mass loss was recorded for the coating on the aluminium substrate whilst the coated 304 stainless steel showed the lowest mass loss. The coatings on brass and super invar experienced similar mass losses. SEM studies of the worn surfaces showed preferential removal of the Co binder phase as well as cracking and rounding of the carbide grains. The differences in wear behaviour may be attributed to the presence of residual stresses where the highest compressive residual stress led to the highest wear rate. The coatings deposited onto brass showed compressive stresses whilst those deposited onto super-invar had tensile stresses, yet these two coatings had similar wear rates. Thus further study is required to provide conclusive evidence of the role of residual stresses on the abrasion resistance of these coatings.

Electrodeposition of Super Invar into Micro- and Nano- Recesses

not Available.

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment

We have developed a senior undergraduate experiment that illustrates frequency stabilization techniques using radio-frequency electronics. The primary objective is to frequency stabilize a voltage controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique is commonly applied to stabilize lasers at optical frequencies. By using only radio-frequency equipment, it is possible to systematically study aspects of the technique more thoroughly, inexpensively, and free from eye hazards. Students also learn about modular radio-frequency electronics and basic feedback control loops. By varying the temperature of the resonator, students can determine the thermal expansion coefficients of copper, aluminum, and super invar.

Electrodeposition of High Aspect Ratio Super Invar Microstructures

Electrodeposition of Super Invar thin films and micro-posts are presented. Different pulse plating parameters were applied and the deposit composition distribution along the length of the microstructures was examined. Pulse plating (−60 mA cm−2, 2 s/ 0 mA cm−2, 27 s) was critical in achieving a uniform composition distribution in 100 micron deep features. Using a pulse scheme with a low, non-zero current step introduced more cracks into the deposit, which were characterized by SEM. The coefficient of thermal expansion (CTE) of the micro-post arrays was also determined and exhibited negative values in the axial direction, i.e., the micro-posts shrink with temperature. Structures with micron size cracks exhibited large, negative CTE values during the first heat cycle of the CTE test and then exhibited less dimensional change with a subsequent heat cycle.