Cryogenic Thermal Cycling Research Articles

Significant rejuvenation of a deformed metallic glass contributed by shear band affected zones during cryogenic cycling

• Shear band affected zones induce significant rejuvenation during thermal cycles. • Semi-in-situ microhardness test confirmed the contribution source of rejuvenation. • Founding an effective method to improve the plasticity of damaged metallic glass. Cryogenic thermal cycling (CTC) treatment is a simple and effective technique to rejuvenate metallic glasses (MGs). However, how the structural heterogeneities of MGs are influenced by CTC is still a problem. In this study, the effects of CTC on mechanical properties and thermal responses of as-cast and as-deformed Zr-based bulk metallic glasses (BMGs) were investigated. Due to the existence of shear bands and their affected zones, the deformed BMG presents greater sensitivity to the CTC treatment, and its softening effect first increases and then saturates with the number of cycles.

Unified upper temperature for cryogenic thermal cycling treatment in Fe-based bulk metallic glasses

Fe-based bulk metallic glasses have high fracture strength and large elastic limit. However, the extremely poor plasticity at room temperature severely renders their wide use as structural materials. In this work, three Fe-based bulk metallic glasses were selected to explore the effect of the upper temperature for cryogenic thermal cycling treatment on the plasticity of the specimens after rejuvenation. It was found that all three Fe-based bulk metallic glasses exhibit the largest plasticity when the upper temperature is about 0.62Tg, where Tg is glass transition temperature. The underlying mechanism is understood by the evolution of the structural heterogeneity dominates by the competition between structural rejuvenation and physical aging during the CTC treatment. When the upper temperature is relatively low, the structural rejuvenation dominates, which causes an increase of the plasticity of bulk metallic glasses; Otherwise, a too high upper temperature leads to a physical aging, resulting in the decline of plasticity. This work will provide process reference for the cryogenic thermal cycling treatment of Fe-based bulk metallic glasses.

Wear reduction of orthopaedic implants through Cryogenic Thermal Cycling

BackgroundMaterial wear caused by relative micromotion of multi-part orthopaedic implants can impact physiology near the implant site and ultimately lead to revision surgery. Cryogenic Thermal Cycling (CTC) is a process that refines and stabilizes the crystal lattice structure of materials by introducing them to temperature modulation cycles that include extremely low temperatures. This method has been proven to significantly improve the performance and wear life capabilities of mechanical components in an efficient, sterile and non-polluting process. This technical note is aimed to evaluate the impact of CTC on wear resistance at head-neck taper connections used in total hip arthroplasty (THA). MethodsMock up components (heads and trunnions) using the same materials representative of THA implants were manufactured for this study. Components were placed into a custom-designed cooling chamber in which they underwent CTC. Short-term Incremental Cyclic Fretting Corrosion (ICFC) testing was conducted on thermally cycled and control (untreated) components, subjected to a full simulated gait with periodically increasing incremental peak loads (modified BioPuls Dual Station ASTM Hip Simulator). Corrosion-related electrical activity was measured for samples with and without CTC. A long-term wear test was also conducted to evaluate corrosion and fretting under double peak compression loading (no rotation). ResultsFrom the short-term tests, samples that underwent CTC showed a significantly reduced corrosion current at the maximum testing compression load of 3,300 N (p = 0.048). The elevated corrosion onset load seen in the treated components did not reach significance (p = 0.152) and no significant difference in the mean change in open circuit potential (OCP) was observed (p = 0.471). Longer-term wear testing found variable differences in CTC and control components with respect to damaged surface areas. ConclusionCTC was shown to be a viable method to reduce short-term corrosion-related electrical activity in THA head-neck taper connections. While consistent differences were not seen in longer-term measures of corrosion, further study is warranted to evaluate the potential of CTC in the context of reducing wear in modular THA implants.

Cryogenic thermal cycling rejuvenation in metallic glasses: Structural and mechanical assessment

Rejuvenation in metallic glasses (MGs) can be achieved by means of thermal cycling treatments at cryogenic temperatures. Here, atomic scale studies were carried out to explore thermal cycling in CuZr MGs at different species contents. Enhanced ductility was observed due to several factors. All samples presented higher potential energy and less-dense structures upon treatments, indicating rejuvenated states. Furthermore, populations of high-centrosymmetric Voronoi polyhedra decreased, while liquid-like structures increased, which are usually related to low rigidity. Atomic connectivity was explored as a measure of the medium range order, revealing that thermal cycling reduced the fraction of 3-atom connections, while increased 2-atom and 4-atom connections. Since 3-atom connections are associated to more-ordered structures, its weakening explains the enhanced plasticity achieved by MGs upon thermal cycling treatments. This study provides new insights into rejuvenation of MGs, delivering atomic scale descriptions at both the short range and medium range order.

Large tensile plasticity induced by pronounced β-relaxation in Fe-based metallic glass via cryogenic thermal cycling

The effects of cryogenic thermal cycling (CTC) treatment on tensile plasticity and structure change of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 metallic glass (MG) ribbons were systematically investigated. Pronounced β-relaxation peaks locating at 643 and 693 K were observed after CTC treatment with diverse thermal temperatures. Specifically, the CTC treated samples exhibiting most remarkable β-relaxation showed tensile plastic strain of 5.2% at 643 K and 4% at 693 K, while the as-quenched sample only showed tensile plastic strain of 3% at 643 K and 2.1% at 693 K. The pronounced β-relaxation and enhanced tensile plasticity are considered to be originated from the increased structural heterogeneity. The separate β-relaxation peaks result from the different sizes/types of shear transformation zones induced by oscillatory (rejuvenation-relaxation) behavior during thermal cycling. Our results indicate that the CTC treatment has a significant impact on the energy states and structural heterogeneity, which makes it a powerful means to modify the mechanical properties of MGs.

Effect of Cryogenic Thermal Cycling on Tribocorrosion Performance of Fe-Based Bulk Amorphous Alloy in 3.5 Pct NaCl Solution

Effect of Cryogenic Thermal Cycling on Tribocorrosion Performance of Fe-Based Bulk Amorphous Alloy in 3.5 Pct NaCl Solution

Evolution path of metallic glasses under extensive cryogenic thermal cycling: Rejuvenation or relaxation?

Rejuvenation of metallic glasses (MGs) under Cryogenic thermal cycling (CTC) has aroused attention due to its prospect of fundamental and practical interest in recent years. However, not all MGs could be rejuvenated by CTC. For some system, obvious rejuvenation is achieved under few number of cycles. While for other system, rejuvenation is hard to achieve and relaxation to lower energy states occurs. The responses of MGs to CTC are so complicated and the inherent dominat factors leading to this situation remains unclear. By extensive CTC (∼800 cycles), the present work discovered quasi periodic characteristics of two typical evolution paths (rejuvenation and relaxation) in MGs, and revealed the different structural origins between them by experimental and simulation. It has been verified that the rejuvenation process induced by CTC comes mainly from local atomic motion in loosely packed regions (LPRs), while the cooperative motion of atoms in densely packed regions (DPRs) is responsible for the other evolution path, i.e., relaxation. Besides, the relaxation path induced by CTC could stabilize the supercooled liquids, with a mechanism different from that underlying the general effect of annealing on marginal MGs. Our finding explains why MGs (even with the same composition) have diverse responses to CTC. It also provides a comprehensive understanding for the mechanism of rejuvenation and a new strategy for modulating the properties of MGs by controlling microstructures by CTC.

Effects of cryogenic thermal cycling on a La-based metallic glass: Relaxation or rejuvenation?

Despite tremendous efforts conducted to reveal the role of cryogenic thermal cycling (CTC) treatment played in the microstructural evolution of metallic glasses (MGs), the underlying mechanisms corresponding to rejuvenation (or relaxation) are still poorly understood. By altering the cycling number and temperature, in the present study, the effects of CTC on hardness and β relaxation behaviors of La60Ni15Al25 MG were evaluated. Intriguingly, the experimental results indicated the cycling number dependence on hardness and the activation energy of β relaxation Eβ following identical trends, and all samples exhibited rejuvenation first and then turned to relaxation after certain cycling numbers. Moreover, it is indicated that the MG with distinct microstructural states could exhibit identical hardness and Eβ, and this unique observation was proposed to be dominated by the mechanism correlated to the shear transformation zone (STZ) size and matrix-path between the percolated STZs.

Enhanced dynamics in deep thermal cycling of a model glass.

We investigate the effect of low temperature (cryogenic) thermal cycling on dynamics of a generic model glass via molecular dynamics simulations. By calculating mean squared displacements after a varying number of cycles, a pronounced enhancement of dynamics is observed. This rejuvenation effect is visible already after the first cycle and accumulates upon further cycling in an intermittent way. Our data reveal an overall deformation (buckling of the slab-shaped system) modulated by a heterogeneous deformation field due to deep cryogenic thermal cycling. It is shown via strain maps that deformation localizes in the form of shear-bands, which gradually fill the entire sample in a random and intermittent manner, very much similar to the accumulation effect observed in dynamics. While spatial organization of local strain may be connected to the specific geometry, we argue that the heterogeneity of the structure is the main cause behind rejuvenation effects observed in the present study.

Cryogenic Accelerated Fatigue Tester for additive manufactured polymer composite mechanical property measurement

Additive manufacturing (AM) of polymer matrix composite (PMC) materials maintains the potential to significantly reduce part count, weight, and costs for future aerospace development. However, a lack of maturity in loading systems has inhibited the characterization of these materials for the cryogenic environment of space. These PMCs demand lifespan endurance when faced with cryogenic thermal cycling in series with high-frequency mechanical loading. Few mechanical testers have been capable of achieving the cryogenic temperatures and actuating frequency to simulate the environment that a PMC endures in a cryogenic application. Also, these testers have yet to define the tensile and fatigue PMC mechanical behavior at these temperatures. To curate a cryogenic, fatigue profile on PMCs, the Cryogenic Accelerated Fatigue Tester (CRAFT) was developed. CRAFT utilizes a 12-kN load frame in unison with a cryocooler to perform tension-tension and tension-compression fatigue tests up to 100 Hz in a liquid hydrogen environment. This publication reviews the CRAFT design and capabilities. Determining the cryogenic fatigue life of 3D-printed PMCs through testing in CRAFT allows for the validation of proper material implementation and the future optimization of these materials in cryogenic environments.

Extra plasticity governed by shear band deflection in gradient metallic glasses

Inspired by gradient materials in nature, advanced engineering components with controlled structural gradients have attracted substantial research interests due to their exceptional combinations of properties. However, it remains challenging to generate structural gradients that penetrate through bulk materials, which is essential for achieving enhanced mechanical properties in metallic materials. Here, we report practical strategies to design controllable structural gradients in bulk metallic glasses (BMGs). By adjusting processing conditions, including holding time and/or controlling temperatures, of cryogenic thermal cycling and fast cooling, two different types of gradient metallic glasses (GMGs) with spatially gradient-distributed free volume contents can be synthesized. Both mechanical testing and atomistic simulations demonstrate that the spatial gradient can endow GMGs with extra plasticity. Such an enhanced mechanical property is governed by the gradient-induced deflection of shear deformation that fundamentally suppresses the unlimited shear localization on a straight plane that would be expected in BMGs without such a gradient.

Rejuvenation in Deep Thermal Cycling of a Generic Model Glass: A Study of Per-Particle Energy Distribution.

We investigate the effect of low temperature (cryogenic) thermal cycling on a generic model glass and observe signature of rejuvenation in terms of per-particle potential energy distributions. Most importantly, these distributions become broader and its average values successively increase when applying consecutive thermal cycles. We show that linear dimension plays a key role for these effects to become visible, since we do only observe a weak effect for a cubic system of roughly one hundred particle diameter but observe strong changes for a rule-type geometry with the longest length being two thousand particle diameters. A consistent interpretation of this new finding is provided in terms of a competition between relaxation processes, which are inherent to glassy systems, and excitation due to thermal treatment. In line with our previous report (Bruns et al., PRR 3, 013234 (2021)), it is shown that, depending on the parameters of thermal cycling, rejuvenation can be either too weak to be detected or strong enough for a clear observation.

Stability of metallic glasses under simulated space conditions

Metallic glasses (MGs), due to their exceptional properties resulting from the amorphous structures, may be potential candidates for space applications. However, the effect of space conditions on the stability of MGs is not clear, which should be taken into account for practical use. The present work assessed the thermal stabilities of MGs in the simulated space thermal fields under vacuum condition, with a specific focus on the cryogenic thermal cycling with a high ratio of the non-isothermal to isothermal durations and the cryogenic treatment for a long-duration. The dynamics and thermal properties of MGs under the simulated space conditions were found to be different than those in laboratory-based conditions. MGs with lower fragility values were also determined to show greater thermal stability. On this basis, rules for the selection of MGs to ensure thermal stability during future space applications were proposed.

Efficient rejuvenation of heterogeneous {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 bulk metallic glass upon cryogenic cycling treatment

The effects of cryogenic thermal cycling on deformation behaviour and structural variation of {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 bulk metallic glass (BMG) were studied and compared with Cu-free [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 BMG. After thermal-cycled treatment between 393 K and cryogenic temperature, the {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 BMG obtained a plastic strain of 7.4% combined with a high yield strength of 4350 MPa. The excellent soft magnetic properties were maintained after CTC treatment. The minor addition of Cu element results in an initial nano-sized heterogeneity in the matrix, which facilitates the rejuvenation process during thermal cycling, and brings to a low optimal thermal temperature of 393 K, making the {[(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4}99.9Cu0.1 BMG more attractive in industrial application. During thermal cycling, the formation of more soft regions leads to the increase of structural heterogeneities, which is beneficial to the initiation of shear transition zones and the formation of multiple shear bands, and thus results in the enhancement of plasticity. This study links the subtle variation of specific structure with macroscopic mechanical properties, and provides a new insight of composition selection for cryogenic thermal cycling treatment.

Hydrophobic and corrosion resistance properties of the electrochemically etched Zr-based bulk metallic glasses after annealing and cryogenic thermal cycling treatment

The effects of annealing and cryogenic thermal cycling treated on hydrophobic properties of Zr-based bulk metallic glasses surfaces fabricated by electrochemical etching were studied. The cryogenic thermal cycling on leads to poor corrosion performance for heat-treated metallic samples, while the annealing treatment induces the improved corrosion performance. Under the same electrochemical etching process, the etched sample surface is covered by dense coral-like micro-nano composite structures after cryogenic thermal cycling treatment for 30 cycles, and achieves superhydrophobic. However, there almost no nanoscale structures appear on the sample surface heat-treated at 702 K which results in the poor hydrophobic properties. Superhydrophobic film can generate a corrosion protection due to the existence of micro-nano composite structures in the samples.

Flow serrations of rejuvenation behaviour through cryogenic thermal cycling for Zr-based bulk metallic glass

ABSTRACT Effects of cryogenic thermal cycling (CTC) on mechanical properties and serrated flow of the Zr52.5Cu17.9Ni14.6Al10Ti5 bulk metallic glass were studied. The improved plasticity, a slightly reduced yield stress and abundant small serrations could be signs of rejuvenation. The high disorder degree result from rejuvenation increases the volume of shear transformation zones (STZs), and thus leads to the enhancement of plasticity. The larger plasticity of BMGs is realised through the superimposed effect of two favourable factors (CTC treatment and strain rate). In this case, the experimental failure threshold is far below the theoretical value. It provides a new idea for designing ductile BMGs.

Tribology of rejuvenated CuZr-based amorphous alloys

Cryogenic thermal cycling was done for the rejuvenation of Cu46Zr47Al7 and Cu45Zr47Al7Ti1 amorphous alloys. The effect of rejuvenation on the tribological behavior of these two amorphous alloys was investigated against Si3N4 ball by reciprocating sliding wear test. A significant improvement in the tribological properties was seen for the rejuvenated Cu46Zr47Al7 alloy, which showed the lowest COF and wear rate among the studied alloys. Rejuvenation resulted in an increase in H/E and H3/E2 ratios, where H = hardness and E = elastic modulus. The Cu45Zr47Al7Ti1 amorphous alloy showed relatively smaller increase in relaxation enthalpy after rejuvenation. The wear mechanisms were determined to be mainly adhesive, fatigue, and oxidative wear. Our results indicate that rejuvenation may be an effective way to improve the tribological performance of metallic glasses both in the form of bulk alloys as well as coatings.

Enhancement of plasticity by cryogenic thermal cycling on Fe80P13C7 bulk amorphous alloy

The effect of cryogenic thermal cycling on the plasticity of Fe80P13C7 bulk amorphous alloy was investigated. The plastic strain increases from 1.7% of the as-cast samples to 5.4% of the cryogenic thermal cycling treated ones, while the yielding strength does not have an obvious deterioration. The enhancement of plasticity can be ascribed to the rejuvenation induced more disordered high-energy states in structure, which corresponds to a creation of excess free volume and therefore helps to the formation of multiple shear bands. This work provides an effective method for the modification of plasticity of Fe-based bulk amorphous alloys.

Decelerated aging in metallic glasses by low temperature thermal cycling

The work presents a combined study on the impact of cryogenic thermal cycling in terms of differential scanning calorimetry measurements on bulk metallic glasses and extensive molecular dynamics simulations of a generic model glass former.

The correlation between β relaxation and shear transformation zone in LaNiAl bulk metallic glasses: The effect of cryogenic thermal cycling treatment

Despite the general acceptance that β relaxation and shear transformation zone (STZ) may share similar microstructure origin and possess identical activation energies, i.e., Eβ = WSTZ, in this study, we experimentally demonstrate opposite changing trends of the two energies could be derived in La60Ni25Al15 metallic glass before and after cryogenic thermal cycling treatment with distinct temperature intervals. Specifically, the experimental results indicate larger STZ requires higher WSTZ, while lower Eβ is needed to activate the atoms involved in string-like motions that corresponding to easier β relaxation. The results of this article will deepen our understanding of the correlation between relaxation and deformation carriers of the La-based metallic glasses.