Solution Hardening Research Articles

Impacts of the alloying elements and thermo-mechanical processing on the phase stability, crystalline structure, microstructure, and selected mechanical properties of Ti-(10-x)Al-xV (x = 0, 2, and 4 wt%) alloys targeted as external prostheses

This study aimed to characterize Ti-Al-V alloys submitted to thermo-mechanical processes and evaluate their impact on the crystalline structure, microstructure, coefficient of thermal expansion (CTE), selected mechanical properties, and cytotoxicity. X-ray diffraction (XRD) analysis revealed a major α phase, with V acting as a β-stabilizer. The cooling rate and the plastic deformation contributed to the formation of minor martensitic αʹ and β phases, with notable variations in cell parameters. The Energy-Dispersive XRD indicated the CTE was dependent on the alloying elements. Ti-10Al and Ti-8Al-2V depicted Widmanstätten laths and basket-weave structures, while Ti-6Al-4V showed typical features of β grain boundaries. Thermodynamic predictions aligned with the observed phase compositions. Vickers micro-hardness tests yielded values surpassing those of commercially pure titanium (CP-Ti), attributed to the synergistic effects of solid solution, phase precipitation, and strain hardening effects. And, elastic modulus approximated that of CP-Ti, largely due to the α phase's predominance. The solution treatment reduced the elastic modulus compared to the hot-rolled samples due to the stress relief and αʹ and β phase precipitation. Preliminary cytotoxicity assays confirmed the non-toxicity of the samples to cell viability. These findings suggest that the solutionized Ti-10Al sample is an economically viable candidate for fabricating external prostheses.

Ultra-strong cold-drawn 2507 stainless steel wire with heterogenous microstructure of dual-phase and grain size

Obtaining ultrafine grains through severe plastic deformation is a highly effective strategy for improving the strength of metallic materials. Due to the different deformation mechanisms between ferrite and austenite, the heavily drawn 2507 stainless steel wire possesses a significant heterogeneous structure at drawing strain ε = 6.65.In this study, a 2507 duplex stainless steel (DSS) with a strength of 2.7 GPa was prepared by cold drawing process. The deformation production of the ferrite in the wire is simply dislocation, which subsequently transforms to subgrain boundary and high angle grains boundary. While the production of the austenite is dislocation and twinning. In addition, based on the boundary strengthening, solid solution hardening and lattice friction, the contribution of the deformed ferrite and deformed austenite to the yield stress is 2260 MPa and 2800 MPa, respectively.

The Influence of Er and Zr on the Microstructure and Durability of the Mechanical Properties of an Al-Mg Alloy Containing 7 wt.% of Mg.

Al-Mg alloys are characterized by permanent solid solution hardening and can additionally be work-hardened. The high mechanical properties of Al-Mg alloys with above-standard Mg content obtained after plastic deformation processes decrease over time. The addition of minor alloying elements like Er or Zr is an alternative method to improve the durability of mechanical properties and increase the strength of Al-Mg alloys due to densely and evenly distributed dispersoids being formed. In this paper, Al-Mg alloys with above-standard Mg content (7 wt.%) and Zr and Er micro-alloying elements and their influence on the microstructure and durability of the mechanical properties were examined. The cast ingots of AlMg7 alloys were characterized by a smooth surface without cracks. The plastic deformation process in a static compression test resulted in an about 60 HBW increase in the Brinell hardness of all the deformed alloys relative to casting. It was revealed that the addition of Er and Zr significantly improved the mechanical properties and durability of the mechanical properties of the Al-Mg after annealing. The addition of Er or Zr slightly restrained the decrease in the Brinell hardness after annealing but did not inhibit it.

Strengthening mechanism and martensite transformation behavior in grain-refined low-Ni austenitic stainless steel

Low-Ni (less than 3 wt%) austenitic stainless steels with different C contents were designed and heat treated to utilize both the grain refinement and carbide strengthening, and their effects were systematically investigated to elucidate the mechanism of tensile property improvement. Grain refinement to 2–3 μm with homogeneously distributed Cr23C6 carbides resulted in excellent combination of yield strength (YS) and tensile elongation (YS × Tensile elongation of nearly 30,000 MPa %) without yield point elongation. The strengthening due to grain refinement was complemented by precipitation hardening. Grain refinement inhibited deformation-induced martensite transformation (DIMT) to decrease the strain hardening rate, while fine Cr23C6 carbides uniformly distributed within austenite grains promoted DIMT and increased strain hardening rate by depleting Cr and C concentrations. Two competing effects of grain refinement and Cr23C6 carbide formation on DIMT resulted in the increase of strain hardening rate as the latter was more dominant on austenite stability. Strengthening mechanisms were clearly explained by quantifying the contributions from solid solution, grain refinement and precipitation hardening. Stacking fault energy and driving force for γ → α’ varied with C contents and annealing treatment, indicating that the optimum combination of C addition and thermomechanical treatment can yield the high performance low-Ni austenitic stainless steels.

Effect of Nb and Ti additions on microstructure, hardness and wear properties of AlCoCrFeNi high-entropy alloy

The use of Nb and Ti in the development of high-performance alloys is strategically important for technological advancement. The effect of Nb and Ti additions on the microstructure, hardness and tribological properties of the High Entropy Alloy (HEA) AlCoCrFeNi was evaluated. The addition of 0.6mol of Nb led to the formation of Laves phase, resulting in a B2/Laves type hypoeutectic microstructure. Conversely, increasing Ti concentration led to the formation of a dendritic microstructure, with interdendritic region composed of Cr-rich BCC-A2 and Fe-Ti rich Laves phase. The average hardness values obtained were 790 HV, 597 HV and 731 HV for AlCoCrFeNiNb0.6, AlCoCrFeNiTi0.5 and AlCoCrFeNiTi1.2 HEAs, respectively. The high hardness was attributed to the formation of the Laves phase and Cr-rich phases, in addition to solid solution hardening, as confirmed by the increase in the lattice parameter calculated by Rietveld refinement method for both B2 and BCC-A2 phases. While the three compositions exhibited comparable friction coefficient, the alloy containing Nb showed superior wear behavior. This was evidenced by the lower volume of material loss and the lower wear rate, which can be attributed to the fine and homogeneous hypoeutectic microstructure observed in the ingot’s cross section. The wear mechanisms were studied, characteristics features of abrasion and adhesion wear were observed.

Physics of hardening of the rolling surface of rail head from hypereutectoid steel after operation

In Russia, with its extensive railway system, for more than 5 years, special-purpose rails of increased wear resistance and contact endu­rance of the DH400RK category were produced from steel with a carbon content >0.8 %. On the head rolling surface of differentially hardened long rails made of hypereutectoid steel after long-term operation, transmission electron microscopy methods revealed the morphological components of the structure: lamellar pearlite, fragmented pearlite, destroyed lamellar pearlite, globular pearlite, completely destroyed pearlite, subgrain structure. The contribution of hardening due to: lattice friction, solid solution hardening, pearlite hardening, incoherent cementite particles, grain boundaries and subboundaries, dislocation substructure and internal stress fields were quantified. A hierarchy of these mechanisms was made and it was noted that for the fillet surface of the rail head, the main hardening mechanism is hardening by incoherent particles, as well as mechanisms caused by internal long-range (local) stresses, internal shear stresses (“forests” of dislocations) and substructural hardening. For the rolling surface along the central axis of the rail head, the main role in hardening belongs to long-range stress fields (especially its elastic component), hardening by incoherent particles and substructural hardening. Taking into account the volume fractions of the morphological components and their yield strength, the additive yield strength on the head rolling surface in the center and on the fillet was determined: 7950 and 2218 MPa, respectively. The paper presents a physical interpretation of the difference in values of the additive yield strength on the rolling surface of the rail head in the center and on the fillet.

Effects of Silicon and Aluminum Alloying on Phase Transformation and Microstructure Evolution in Fe–0.2C–2.5Mn Steel: Insights from Continuous–Cooling–Transformation and Time–Temperature–Transformation Diagrams

The impact of silicon and aluminum on phase transformation behavior, particularly bainite, and microstructure evolution in Fe–0.2C–2.5Mn steel are presented. Continuous–cooling–transformation (CCT) and time–temperature–transformation (TTT) diagrams are determined experimentally. An aluminum extended empirical formula is introduced to estimate the martensite start temperature (Ms) with a thorough assessment of existing formulae. Results show that aluminum significantly increases Ms and has a stronger influence on promoting ferritic microstructures than silicon. During continuous cooling, alongside bainite, formation of Widmanstätten structures is induced in aluminum‐alloyed steel at higher cooling rates due to increased prior austenite grain size. Silicon decelerates bainite transformation kinetics by enhancing austenite's chemical stability through carbon enrichment via preventing carbide precipitation and by strengthening austenite against displacive phase transformation via solid solution hardening. Although aluminum has similar effects, incubation time is shortened during isothermal treatment because of the increased driving force, which overcompensates for the retardation effects. A finer carbide‐free bainitic microstructure is achieved in aluminum‐alloyed steel with more pronounced film‐like retained austenite (RA) formation and superior carbon enrichment, improving RA stability and suppressing martensite–austenite island formation. Finally, with the proposed formula, an accurate approximation to experimental Ms is accomplished.

Efficient alloy design strategy for fast searching for high-entropy alloys with desired mechanical properties

The exponentially large compositional space of high entropy alloys (HEAs) offers more possibilities for designing alloys with desired properties. However, it also poses challenges to using the traditional “trial and error” approach in alloy design. In this work, an XGBoost model for predicting the elastic properties of the NbTiVZr family across the entire compositional space was established by combining density-functional theory (DFT) calculation results as the dataset with machine learning (ML) algorithms. Furthermore, considerations of charge transfer were incorporated into the solid solution hardening (SSH) model, and the model was further modified. Through comparing plasticity evaluation indices, the parameter D (γSurf/γGSFE) was determined to be suitable for predicting the plasticity of NbTiVZr alloys. A full compositional space model for yield strength and plasticity has been constructed based on the modified SSH model and the parameter D, respectively. Ultimately, an alloy design system combining the full compositional space models for yield strength and plasticity was established, achieving good consistency with experimental results. And a non-equiatomic alloy with a yield strength exceeding that of equiatomic alloys by 32.2 % (1409 MPa), while maintaining 29.27 % compressive strain was discovered. In conclusion, this work provides an efficient design strategy for alloys with desired properties.

Precipitation behavior and strengthening mechanism in a Cu-3.5Ti-0.1 Tm alloy

The study investigates the complex relationship between precipitation patterns, microstructural evolution, and mechanical properties in a Cu-3.5Ti-0.1 Tm alloy subjected to isothermal ageing. The results reveal that ageing at 450 °C leads to the formation of nanoscale β′-Cu4Ti phase particles within the grains and fibrous β-Cu4Ti precipitates along the grain boundaries. The precipitation microstructure of this aged alloy is predominantly characterised by tetragonal β′-Cu4Ti precipitates. During spinodal decomposition, Ti atoms segregate in rod-like Ti-rich Cu phases, facilitating their conversion into β′-Cu4Ti phase. The β′-Cu4Ti precipitates remain fully coherent with the Cu matrix, exhibiting a crystallographic orientation relationship of (001)Cu//(001)β′ and [100]Cu//[130]β′. As the precipitate radius exceeds approximately 11 nm, the elastic strain energy surpasses the energy at the precipitate/matrix interface. This leads to a shape transition from spherical to cuboidal for the β′-Cu4Ti precipitates. Moreover, the Ti solute atoms contribute significantly to the alloy's strength through solid solution hardening, with the dissolution of 1 at.% Ti solute increases the yield strength by 46.2 MPa. However, as ageing progresses from 1 to 20 h, the effect of solid solution strengthening decreases, while precipitation strengthening becomes more dominant, mainly due to the Orowan bypass mechanism. After 20 h of ageing, precipitation strengthening significantly increases the yield strength by about 436 MPa, exceeding the contributions from solid solution strengthening (78 MPa) and grain-boundary strengthening (14 MPa).

Influence of post-deformation annealing conditions on microstructures and mechanical properties of hypereutectoid steel wires during cold drawing

Abstract This investigation delves into the complex influences of annealing conditions post-deformation, such as duration and heat levels, upon the microstructure, as well as the mechanical properties of hypereutectoid steel wires subjected to cold drawing. XRD and VSM analyses confirmed that higher annealing temperatures precipitated a notable increase in cementite volume, concurrently inducing the spheroidization of cementite lamellae. This transformation was evidenced by the expansion of cementite volume and the transition of cementite layers into a spherical morphology as the annealing temperature increased. The evolution of tensile strength in response to varying annealing temperatures and time revealed two distinct patterns. Initially, at lower annealing temperatures ranging between 200°C and 300°C, tensile strength exhibited an upward trajectory with increasing annealing time. This phenomenon can be attributed to age-hardening mechanisms, notably associated with solution hardening. As annealing time increases, the decomposition of cementite releases additional carbon atoms into the ferrite matrix. These carbon atoms act as effective barriers, hindering dislocation movement within the structure and consequently contributing to increased tensile strength. However, this increase in carbon content within the ferrite matrix also elevated the susceptibility to delamination phenomena. Conversely, at higher annealing temperatures of 400°C and 500°C, a contrasting trend was observed, characterized by a consistent decline in tensile strength post-annealing. This decline could be attributed to the phenomenon of aging softening, wherein the process of spheroidization and re-precipitation of cementite resulted in a reduction of dissolved carbon atoms within the ferrite matrix. Consequently, this led to a decline in tensile strength as well as a reduced incidence of delamination. In summary, the study explored how different annealing conditions affect the structure as well as the strength of hypereutectoid steel wires, revealing detailed mechanisms behind these changes.

Enhancing strength and ductility in Fe–20Mn–9Al-1.5C austenitic low-density steels through Ni and Cr alloying synergy adding

In this investigation, a Fe–20Mn–9Al-1.5C lightweight austenitic steel has been developed through strategic alloying with Ni and Cr elements coupled with the employment of a thermo-mechanical processing technique featuring ultra-fast cooling. This composition and treatment synergistically transcend the conventional trade-off between strength and ductility, positioning the mechanical performance of this steel notably above that of comparable low-density austenitic steels previously reported. The coordinated incorporation of Ni and Cr is key to modulating the precipitation threshold for nanoscale κ-carbides and LRO domains, achieving an optimal size for precipitate-induced strengthening. The incorporation of Cr specifically contributes to a dual enhancement mechanism: it fosters the generation of high-density dislocation arrays (HDDA) and refines the dynamic slip band (DSBR) during deformation, which in turn, elevates the strain hardenability and ductility. The remarkable synergy in strength and ductility is attributed to a combination of mechanisms including grain boundary reinforcement, solid solution hardening, the precipitation strengthening effect of nanoscale precipitates, and the activation of secondary slip system dislocations. This synergy is quantitatively reflected in the material's yield strength (YS) exceeding 1100 MPa, ultimate tensile strength (UTS) surpassing 1200 MPa, and a total elongation (TEL) exceeding 45%. The insights gained from this research provide critical guidance for the design and creation of austenitic low-density steels that do not compromise between strength and ductility, thereby offering superior overall performance.

Solute Hardening and Softening of BCC Metals: Excerpts from an Early Life with Terry Mitchell

Solute Hardening and Softening of BCC Metals: Excerpts from an Early Life with Terry Mitchell

High-throughput strategy to design high entropy alloys with an FCC matrix, L12 precipitates, and optimized yield stress

This work proposes a methodology for designing high-strength precipitation-hardened high entropy alloys (HEAs) with an FCC matrix and L12 precipitates. High-throughput solidification calculations were conducted using the CALPHAD method, evaluating 11,235 alloys in the Cr-Co-Ni-Al-Ti system under specific boundary conditions. The acquired information was used to filter the alloys, focusing on alloys exhibiting an FCC+L12 phase field at 750 °C, a solidification interval narrower than 100 °C, and a solvus temperature under 1100 °C. The filtered alloys were analyzed to estimate their solid solution and precipitation hardening contributions to yield strength, with antiphase boundary energy (APB) assessed using two models. Three alloys were selected for testing the proposed strategy, including one with the highest yield stress and others for comparison. These alloys were produced, processed, and characterized using DSC, synchrotron XRD, SEM, and TEM. The results showed that the desired microstructure was achieved, with the alloys consisting of an FCC matrix and a high-volume fraction of L12 precipitates. Tensile tests at room temperature, 650 °C, 750 °C, and 850 °C demonstrated that the proposed model predicts well the yield strength trends, demonstrating the potential of the proposed approach for accelerating the discovery and development of novel HEAs with tailored properties.

Novel bainitic Ti alloys designed for additive manufacturing

Novel ternary titanium alloys with a bainitic microstructure have been designed specifically for additive manufacturing (AM). The Ti-xCu-yFe alloys take advantage of constitutional supercooling to suppress the growth of large columnar grains usually associated with AM Ti alloys. In the as-built condition the bainitic microstructure consists of a refined α-phase within a matrix of β-phase. The intermetallic phase, Ti2Cu, forms predominantly on the interface of the α- and β-phase and within the β matrix. The high strength of these materials is attributed to the refined α-phase and Ti2Cu particles as well as significant solid solution hardening. This work demonstrates a viable way to fabricate structural components with unique and excellent properties using low-cost elemental powders with AM.

Parameter-determined interface morphologies and properties of explosively-welded Cu–Ni–Si–Cr alloy composites

Six Cu–Ni–Si–Cr alloy composites are prepared by explosive welding with the designed parameters. Wavy interface containing the melted pockets and shrinkage cracks is always observed, refining the grains to just several micrometers with the localized deformation. Resultantly, the interface regions show higher hardness and yield strength than elsewhere, reaching HV 190 and over 400 MPa, respectively, but their plasticity is less than half that of the base-plate parts. Theoretical analysis successfully relates the area of the total disrupted regions including the interfacial molten and wavy zones in the composites linearly to the flyer-plate thickness (hf) and collision angle (β) as (hfsin2β2)2. For the composite fabricated at an impact velocity and angle of 310 m/s and 8.0°, respectively, strengthening mechanism calculation for its interface part reveals that grain boundary, dislocation and solid solution hardening are most effective and contribute 68 MPa, 370 MPa and 39 MPa individually, making the dislocation hardening dominant for the enhanced strength.

Novel compounds in the Sc-rich part of the systems Sc-{Co,Pd,Pt}-Ga: Structure and bonding

The present paper comprises a detailed structural analysis of two novel compounds in the Sc-Co-Ga system: τ3-Sc50Co13Ga3 (space group Fm-3; ε-Mg26-xAg7+x type), and τ4-Sc6Co1.73+x+yGa1-x (space group Immm; x=0.43; y=0.14; Ho6Co2Ga derivative type). Although alloys in the isothermal section are oxygen-free, the alloy of τ3, prepared for single crystal growth via partial melting in an alumina crucible, contained a minor amount of oxygen and can be considered as oxygen-stabilized Sc50Co13Ga3O1.1 (WDX-data). A search for homologous compounds in the systems Sc-{Pd,Pt}-Ga prompted the existence of two compounds Sc54{Pd,Pt,Ga}17, which from X-ray single crystal analyses proved both to be isotypic with the Hf54Os17-type structure (space group Immm). Whereas Sc54(Pd0.652Ga0.348)17 has a very limited homogeneity region at 850°C, Sc54(Pt1-xGax)17 exhibits at 850°C a large homogeneity region (0<x<0.28) extending from Ga-rich Sc76Pt17.2Ga6.8≡Sc54(Pt0.72Ga0.28)17 to novel binary Sc54Pt17. Interestingly, against the usual trend of solution hardening, hardness, Young's modulus and fracture toughness all decrease with increasing Ga-content: this effect is less pronounced for Sc54(Pd1-xGax)17 than for Sc54(Pt1-xGax)17 and is in line with DFT calculations indicating a weakening of bonding with increasing Ga content, thereby overcompensating the solution hardening effect. DFT modeling showed a common bonding feature for all the studied compounds – a strong electron localization inside the Sc6 octahedra, stacking of which leads to the formation of Mackay icosahedra in Sc54(Pd1-xGax)17, Sc54(Pt1-xGax)17, and Sc50Co13Ga3. The band structure of Sc6Co2.25Ga0.625 and Sc50Co13Ga3 indicates their metallic behavior, while Sc54(Pd1-xGax)17 and Sc54(Pt1-xGax)17 show distinct semimetal features. All investigated compounds in this work show similar trends in Bader charge distribution with a positively charged Sc-sublattice and a negatively charged sublattice formed by transition metals (Co, Pd, Pt) and Ga.

Mitigation of strength-ductility trade-off of CoCrNi medium entropy alloys with heterogenous structure by controlled Gd addition and annealing

In this work, we synthesized a series of (CoCrNi)100–xGdx (x = 0/0.3/0.5/1.0) medium entropy alloys (MEAs) using arc melting followed by homogenization, hot-rolling, and annealing at 700, 800, and 900 °C for 1 h. The effects of Gd content and annealing temperature on the microstructures and mechanical properties of Gd-doped CoCrNi MEAs were investigated. The heterogenous microstructure, consisting of the deformed grains, recrystallized grains and precipitates of GdNi5 phase, was obtained in the present study and it exhibited an excellent combination of strength and ductility. The optimum mechanical properties were obtained for CoCrNi MEA with 0.3–0.5 at.% Gd addition and annealed at 700 °C for 1 h to yield the heterogenous microstructure in the present study, and it had the tensile strength of ∼1.3 GPa and fracture strain of 30–40%. The synergetic hardening mechanisms included solid solution, precipitation, grain refinement, nanotwinning and pre-existing dislocation hardening. The relations among compositions, microstructures and mechanical properties of (CoCrNi)100–xGdx MEAs were addressed.

Development of TiNbMoMnFe multi-principal element alloy coating using mechanical alloying and HVOF thermal spray

Multi-Principal Element Alloys (MPEA) were designed to possess good strength, ductility, wear and corrosion resistance, and biomedical compatibility. There are many applications where failure is associated with surface-related degradation, and suitable coatings can mitigate them. This study focuses on the development of MPEA coatings using the HVOF thermal spray process and explores their mechanical and tribological responses. In the present study, the transitional and refractory elements-based feedstocks were prepared by a mechanical alloying process using a high-energy ball mill for 5 h, 10 h, and 15 h milling time. The molar ratio of the developed coating was TiNbMoMnFeOX (1:1:1:1:1:X, where X = 0.48 to 0.62). Thus, prepared feedstock powders and coatings were characterized to record their metallurgical, mechanical, and tribological responses wherever it is applicable. The used scientific tools include X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), universal tribometer, and nanoindenter set-up. The results showed that mechanical alloying led to the formation of MPEA, and the 15 h milled MPEA powder coating expressed superior performance. Furthermore, the process exhibited significant microstructural changes in the alloy system, and dual (TiNb and TiMo) and ternary (TiNbMo) BCC phases were developed during the process. These BCC phases were responsible for the coating's improved mechanical and tribological responses. The solid solution hardening of the ternary phase (TiNbMo) was the most dominant mechanism for improving the mechanical and tribological properties.

Mechanism of solute hardening and dislocation debris-mediated ductilization in Nb-Si alloy

Niobium (Nb) is sensitive to even minute quantities of silicon (Si) solutes, which are known to induce pronounced hardening. However, the underlying mechanism for hardening remains elusive since the effect of Si solutes on dislocation behavior is unclear. Here, using tensile testing, in-situ microscopy and nanomechanical testing, the behavior of dislocations in dilute Nb-Si alloys, containing from 0 at.% to 0.8 at.% Si, is investigated. We show that the hardness, strength and strain hardening rate increase from two to four times, while the uniform elongation in tension only reduces 50 % as the Si content increases. Dislocations evolve from complex entangled patterns in Nb to parallel long-straight screw dislocation-dominated structures in Nb-Si alloys. In-situ indentation reveals that the origins of the marked hardening in Nb-Si alloy are the reduction of dislocation mobility and cross-slip propensity. Large densities of dislocation debris-superjogs and loops introduced throughout the sample during warm rolling and annealing are found to provide active internal dislocation sources, which explain the minimal ductility loss seen in these Nb-Si alloys. These findings can help guide the alloy design of high-performance refractory materials for extreme temperature applications.

Recoverable tuning of lattice mismatch and strength in ultrastable-nanostructured Cu/Ag spinodoid alloys

The strengthening effect of interface in materials is usually studied by monitoring the change of strength in response to varying structure sizes, such as the varying grain or phase sizes. In this study, we demonstrate that the strength of a nanostructured material can be recoverably tuned by modifying interfacial structure without changing structure size. Specifically, we studied the Cu/Ag spinodoid alloys fabricated by dealloying and electrochemical deposition, which exhibit a cube-on-cube orientation relationship between two interpenetrating nanophases. This material remains stable against coarsening even at temperatures near the eutectic melting point, due to the presence of low-energy semi-coherent interfaces and the lack of defects such as grain boundaries. Using cyclic thermal annealing, we are able to alter the solid solubility of both nanophases and, consequently, the lattice mismatch between them, resulting in a recoverable tuning of hardness and strength. The amplitude of hardness modulation decreases with increasing feature size (λ), and changes sign when λ exceeds ∼500 nm. This is attributed to a competition between two strengthening mechanisms: the interface-induced strengthening that is more prominent at a lower λ, and the solid solution hardening that is largely λ-insensitive. The finding indicates that interface hardening prevails over solution hardening when λ is below ∼500 nm. Current study paves the way for the development of strong and stable nanostructured materials whose properties can be optimized by independently tailoring feature sizes and interfacial structures.