Increase Of Holding Time Research Articles

Study on the mechanical and low‐temperature degradation properties of 3Y‐TZP doped with nano‐MgO by microwave sintering

AbstractThe effects of nano‐MgO content on the microstructure, phase composition, mechanical properties of 3 mol% yttria‐stabilized tetragonal zirconia polycrystal ceramics were studied by microwave sintering at 1300°C–1500°C for 15–120 min. The low‐temperature degradation resistance of the samples was evaluated by hydrothermal experiments. Samples direct microwave sintered at 1500°C for 1 h attained a relative density between 95.5% and 98.2%, with an average grain size of 0.32–0.48 µm, the phase composition was identified as tetragonal ZrO2, with a bending strength of up to 822.07 MPa and a microhardness of 1784.22 HV, with the average friction coefficient ranging from 0.132 to 0.432. Hybrid microwave sintering at 1500°C with 0.8 wt% MgO attained a relative density (94.1–95.4%) and grain size (0.25–0.29 µm) with holding time increases from 15 to 45 min. After hydrothermal treatment at 134°C/0.2 MPa for 60 h, the monoclinic phase content of the samples by direct microwave sintering held at 1500°C for 1 h decreased from 41.43 vol% to 17.85 vol% with the increase in the content of nano‐MgO, indicating that microwave sintering combined with nano‐MgO significantly inhibits the low‐temperature degradation of zirconia composite ceramics.

Evolution mechanism of Ti(C,N)-based cermet microstructure under microwave sintering

Experimental studies of microwave-sintered cermets were carried out at different sintering temperatures and holding times to investigate their microstructure evolution mechanism. Results of the study show that: (1) As sintering temperature increases, main microstructure evolution mechanisms of cermets are as follows: metal-phase melting, hard-phase skeleton filling of large pores in hard-phase skeletons, secondary rearrangement of the liquid phase (the liquid phase gradually fills the space between grains), and cooling down (precipitation–crystallization–reattachment); (2) As holding time increases, main microstructure evolution mechanisms of cermets are as follows: complete filling of large pores in the hard-phase skeleton, secondary rearrangement of the liquid phase, intense dissolution precipitation enhancing the formation of core-rim phase, and secondary homogeneous arrangement of the liquid phase. The special electromagnetic effects of microwave-sintered cermets and their influence on the sintering process were analyzed. It was found that both tip-discharge effect and hot-spot effect occurring during the microwave sintering process are conducive to the sintering process. The formation process of core-rim phase of cermets was also studied. Results show that: (1) Cermets form black core–white rim–grey rim structure via dissolution–precipitation and precipitation–crystallization phenomena; (2) Cermets form white core–grey rim structure through agglomeration of small particles, dissolution–precipitation, and precipitation–crystallization phenomena.

Flash sintering of UO2 pellets for nuclear fuel and wasteform applications

Flash sintering (FS) has been shown to enhance the sintering kinetics in UO2. Using a bespoke AC-FS furnace, high density UO2 pellets, >95 % theoretical density (TD) have been produced followed by scale up and Gd2O3 doping trials. Increasing furnace temperature during FS increases pellet density to a plateau, however, increasing hold time and maximum current both increased the density of UO2 samples to >95 % TD and grain size to ∼4 µm, close to conventional sintering (CS). The optimised FS program reduced sintering temperature and cycle time by ∼50 % compared to CS. Scale up trials showed >96 %TD pellets could be achieved for 11.3 and 14.125 mm diameter green bodies, demonstrating typical fuel pellet diameters are feasible with FS. Gd doping experiments showed with 1 wt% Gd2O3 addition, a ∼92 %TD pellet with ∼2 µm grain size was obtainable, highlighting further optimisation is required for mixed oxide (MOx) materials.

Interfacial reaction between the nickel-based superalloy and the Al2O3 crucible during vacuum induction melting

The effects of holding time on the interfacial reaction between a nickel-based superalloy and an Al2O3 crucible during the vacuum induction melting process were studied at 1450 °C. The results show that the reaction products at the interface are intermittently distributed and then gradually become dense and continuous as the holding time increases. The average thickness of the reaction layer increases and then decreases when the melting time is extended. Through microstructure characterization, the interfacial reaction layer extending from the boundary to the matrix consists of a continuous Al2O3 reaction layer and a discontinuous TiC layer. Finally, the process of the interface reaction is summarized.

Effect of isothermal holding time on microstructure, precipitates and hardness of Ti–V–Mo microalloyed steel during coiling process

The microstructural evolution, precipitation behavior, and hardness variation of the Ti-V-Mo complex microalloyed steel during isothermal holding following austenite deformation have been investigated using thermal simulation tester (Gleeble-3800), optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), transmission electron microscope (TEM), and Vickers hardness tester. The results indicate that the microstructure transforms from austenite to ferrite as the holding time increases from 0 s to 5400 s at 630 °C, with the microstructure primarily comprising martensite and ferrite. The proportion of ferrite continues to increase, while the proportion of martensite decreases. At a holding time of 600 s, the austenite has nearly completed the ferrite transformation (95%), and the average grain size is very fine (3.9 μm). At this point, the (Ti, V, Mo)C particles exhibit the highest density and a smaller size (7.7 nm), with the hardness reaching its maximum value (415 HV). Concurrently, numerous spherical precipitates particles with a size of < 10 nm formed in the ferrite region, conforming to the Baker–Nutting (BN) orientation relationship with respect to the matrix: (100)(Ti, V, Mo)C//(100)α-Fe, [011](Ti, V, Mo)C//[012]α-Fe. As the holding time increases from 30 s to 60 s, the hardness decreases rapidly due to the reduction of martensite and addition of soft-phase ferrite. However, the subsequent slow decrease in hardness is primarily attributed to weakened precipitation strengthening caused by precipitates coarsening and decreased grain refinement strengthening due to the slight increase in ferrite grain size as the holding time increases from 600 s to 5400 s.

Numerical investigation of deformation and residual stress in vacuum brazing of titanium alloy plate-fin structure

Various high-end equipment relies on titanium alloy plate-fin structure (PFS) as core components, owing to their remarkable advantages in terms of low density, superior mechanical strength and enhanced corrosion resistance. Brazing assumes a pivotal function in PFS connections, whereby the localized concentrated heat during the welding procedure can precipitate intricate structural deformation and generate residual stresses. A thermo-mechanical coupling model was developed, taking into account the service performance criteria of PFS. The effects of process parameters and clamping methods on the post-welding residual stress and deformation of PFS were investigated. The analytical expressions for the relationship between the process parameters and the stress/deformation were obtained by using the simulation outcomes. The constraint on the partition in the vacuum brazing process determines the extent of deformation and residual stress of PFS, with higher constraint leading to lower values. PFS generates z-directional displacement and y-directional warping deformation, and the weld seam between the fin and the partition is prone to stress concentration. As the brazing temperature and holding time increase, the PFS induces more deformation, while the residual stress value decreases. However, the deformation amount reaches a plateau when the holding time exceeds 30 min.

Investigation on microstructure and mechanical properties of GH5188 superalloy TLP joints using nickel based alloy interlayer

GH5188 was bonded successfully with a commercial BNi-2 interlayer through transient liquid phase (TLP) diffusion bonding. The characteristic bonded joint was formed by following three characteristic zones: diffusion affected zone (DAZ) mainly consisting of boride precipitates, athermal solidification zone (ASZ) composed of multiple silica-boride phases and isothermal solidification zone (ISZ) containing γ solid solution phases. As the holding time increases, ISZ gradually replaced ASZ and a defect-free joints was obtained then. However, excessive holding time can cause ASZ to reappear because of the extravagant dissolution of the base metal. The joints’ shear strength from 574 MPa (1190 °C/5 min) increased to 777 MPa (1190 °C/60 min), and the fracture location shifted from ASZ to DAZ with the fracture mode transferred from cleavage fracture to mixed fracture.

Influence of heat treatment on microstructure and thermo-physical properties of Al-50wt%Si alloy fabricated by selective laser melting

Herein, we investigate the influence of heat treatment on microstructure and thermo-physical properties of Al-50wt%Si alloy fabricated by selective laser melting (SLM). Microstructure characterizations reveal that SLM and heat-treated Al-50wt%Si alloys are all characterized by the primary Si and eutectic structure consisting of dominant Al matrix and tiny eutectic Si. However, the size of primary Si monotonously increases with increasing the heat treatment holding time at 550 °C. In addition, the SLM Al-50wt%Si alloy displays a highest coefficient of thermal expansion (CTE) among all examined alloys. As the heat treatment holding time increases, the Si precipitates from the Al(Si)-supersaturated solid solution, leading to the formation of a skeleton-like Si phase, which effectively alleviates the thermal expansion. Furthermore, the SLM Al-50wt%Si alloy exhibits a lowest coefficient of thermal conductivity (CTC), since the significantly increased size of primary Si with increasing the heat treatment holding time leads to a substantial reduction in the number of grain boundaries, which severely restricts the scattering of heat transfer phonons. Moreover, theoretical models are employed to calculate the CTE and CTC. Results indicate that the Schapery lower model provides a better prediction of CTE, and the actual CTC values of Al-50wt%Si alloys after heat treatment are closer to theoretical values. These findings can provide new insights into designing Al matrix composites with low CTE and high CTC through microstructural optimization.

Ultrasonic scattering behavior in austenitic NiTi with varying grain size and precipitate characteristics

Shape memory alloys like NiTi exhibit high strain recovery due to a reversible martensitic transformation when cooled or stressed, enabling actuation and biomedical applications. The characteristics of the stress-induced martensitic transformation in Ni-rich NiTi depend on the heat treatment. For example, aging induces the precipitation of Ni;4Ti;3 and lowers the critical stress needed for martensitic transformation. However, comprehensive characterization of these nanoscale precipitates is challenging as only small areas can be inspected efficiently. Ultrasonic immersion testing may assist in developing linkages between structure and transformation behavior as ultrasonic scattering is sensitive to the microstructure and easily mapped on the bulk scale. To this end, the ability of scattering behavior to discern between different precipitation characteristics must be probed to establish the sensitivity of ultrasonic parameters to changes in precipitation. This work explores the dependence of wave speed, attenuation, and backscattered energy on varying annealing and aging heat treatments of Ni-rich NiTi. The annealing treatments result in a gradient of grain sizes, while the aging treatments result in nucleation and growth of precipitate phases with increasing hold time. Variations in the ultrasonic parameters elucidate the sensitivity to changes in the microstructure, which are more quantitatively explored through existing analytical scattering models.

Low cycle fatigue and creep-fatigue interaction behavior of 2.25CrMoV steel at high temperature

This paper presents a comprehensive investigation into the low cycle fatigue (LCF) and creep-fatigue interaction (CFI) behavior of 2.25CrMoV steel at an elevated temperature of 455 °C. The LCF tests are conducted using a triangular waveform with varying strain amplitudes ranging from 0.4 % to 0.7 %. Furthermore, the CFI tests are conducted using a trapezoidal waveform with different hold times and hold directions. To gain further insights, the microstructure and fracture behavior of the steel are characterized using optical, scanning, and transmission electron microscopy techniques. The results reveal that the softening behavior and fatigue life degradation of the steel are dependent on the applied strain amplitude, hold time, and hold direction. Higher strain amplitudes in the LCF tests lead to an increased number of crack initiation sources. During the CFI tests, fatigue fracture is identified as the primary failure mechanism under tensile hold conditions, and an increase in hold time promotes crack propagation. The interaction between fatigue and creep is found to be more significant in compressive hold and tensile compressive combination hold conditions. Microstructure analysis demonstrates that the lath structure recovers during cyclic loading, resulting in cyclic softening. Finally, a modified energy-based model is proposed to distinguish the different roles of tensile energy and compressive energy in the fatigue process. The proposed model accurately predicts the fatigue life of the 2.25CrMoV steel, as demonstrated by the good agreement between the experimental and predicted results.

Microstructure evolution and strengthening mechanism of γ′-strengthening superalloy prepared by laser powder bed fusion

Recently, γ′ phase has been introduced into the solid-solution strengthening Haynes 230 alloy to improve alloy strength for better satisfying the rigorous service environment. However, previous research shows that γ′ phase was not precipitated under the as-fabricated condition and harmful Laves phases with high-W content, which have never been reported, appeared in the novel alloy. Therefore, in this study, Laves phase dissolution mechanisms during solution heat treatments (SHT) and γ′ strengthening mechanism after subsequent aging heat treatment (AHT) of a novel γ′-strengthening superalloy prepared by laser powder bed fusion (LPBF) were first investigated. The results show that Laves phases continue to dissolve with the increment of SHT temperature and finally disappear after SHT-ed at 1200 °C. The higher dissolution difficulty of Laves phases is closely related to the lower diffusion coefficient of W element. The long-range diffusion of solute atoms mainly controls the dissolution of Laves phases in the early homogenization stage. As the holding time increases, the γ/Laves interface widths for the solute atoms diffusion decrease and thus the dissolution process is gradually governed by the interface reaction in the later stage. After AHT, numerous nanosized γ′ particles are precipitated. With increasing SHT temperature, the ultimate tensile strength (UTS) and yield strength (YS) of the AHT-ed samples decrease while the elongation (EL) increases, which is mainly caused by the Laves phases dissolution and grain recrystallization. The 1200+AHT sample presents an excellent combination of strength and ductility with UTS of 1467.7 MPa, YS of 1244.6 MPa and EL of 6.3%. The dominant strengthening contributions in the AHT-ed samples are γ′ strengthening and solution strengthening.

Mechanisms for creep rupture of 12Cr/alloy 4715 dissimilar weldments

The mechanism for creep rupture of 12%Cr /alloy 4715 welded joints was investigated by employing traditional uniaxial tensile creep in this study. The creep tests were maintained at 580 °C with creep loading stresses gradually decreasing from 300 to 240 MPa, and the time to failure was tested. The rupture location shifts from base metal (BM) to BM + fusion line (FL) then to FL + fine grain zone + coarse grain zone (CGZ), and finally to FL + CGZ as holding time increases. Meanwhile, a softening phenomenon is also observed in the heat-affected zone (HAZ) in crept specimens for a more extended holding time, where voids, carbides, and dislocation density are further discussed. The carbides are identified as Cr and Mo-rich M23C6 type, which forms mainly at grain boundaries during creep testing. In HAZ, M23C6 gradually increases and coarsens, providing nucleation sites for creep voids. Finally, the Larson–Miller parameter method is employed to provide a theoretical reference for predicting use cases that satisfy the industry service condition.

Investigation of some thermomechanical processing effects on the structure and properties of a TiNiCu shape memory alloy

A Ti50Ni45Cu5 shape memory alloy (SMA) was cast, homogenized and hot rolled into 0.5 mm-thick lamellas. After homogenization, the intercrystalline Ti2(Ni, Cu) based solid solution, gradually decomposed with the increase of hold temperature and time, as pointed out by optical, scanning electron and atomic force microscopy. After hot rolling, by wire spark erosion, rectangular specimens with the dimensions 0.5 mm × 2 mm × 6 mm were cut each one with a mass of 0.44 g. Since the specimens experienced a thermoelastic martensitic transformation, while being martensitic at room temperature (RT) they were soft and could be easily bent against cylindrical calibers, in order to induce their “cold” (martensitic) shape. When heated, up to 100 °C with a hot air gun, they readily recovered, by shape memory effect (SME) their initial straight form, also known as “hot shape”. Thermomechanical training cycles were subsequently applied, consisting in: (i) RT bending; (ii) hot air gun heating and (iii) air cooling. These cycles were repeated up to 50 times. The effects of the thermomechanical training cycles were subsequently analyzed, by differential scanning calorimetry, on fragments cut from the active sections of the specimens. It was noticed that training basically increased thermal hysteresis. Finally, experiments were performed which demonstrated the capacity of Ti50Ni45Cu5 SMA elements to develop.

Quantitative kinetic analysis of γ′ precipitate evolution in a Co–Al–W superalloy during aging heat treatment

In this research, the effect of aging-heat treatment on evolution of γ′-precipitates in the Co–Al–W-based superalloy was studied. For this purpose, solution heat treatment was applied followed by water-quenching and then, aging different cycles were carried out at four temperatures of 720, 780, 840 and 900 °C for different holding time (1–48 h). The electron microscope micrographs showed that increasing size of γ′ particles happens with more holding time; while volume fraction stays approximately constant at 0.72. In addition, the γ-γ′ lattice mismatch, as positive values, increased with holding time increase due to simultaneous γ′ shape adaptation. While the γ′ morphology variation was seen to change from spherical to semi-cubic and cubic; the L- and stretched-shapes of γ′-particles with concurrent split of the coarse particles was detected by coarsening, coalescence and splitting phenomena, respectively. The proposed mechanisms for such microstructural evolution were interpreted based on n value as the power term in kinetics equation. As such, the γ′-particles diffusion across the γ/γ′ interface (n∼2), volume-diffusion (n∼3) and coalescence/splitting (n∼7) are key controlled processes at different aging temperature ranges. The characteristics of γ′-precipitates was discussed in detail based on total energy concept in terms of surface (Esur.), elastic strain (Estr..) and interactions of elastic (Eint.) energies and hence, a phenomenological model was proposed for evolution of γ′-particles. Modeling based a physical model and analysis of microhardness experimental revealed that the desired radius of γ′ phase should be between 80 nm and 90 nm respectively; and the optimized aging condition is estimated to be done at 840 °C for 36 h.

Study on the nucleation and growth of In2O3 powders for oxide ceramic targets

In this work, the precipitation nucleation and the growth mechanism during the preparation of In2O3 powders are studied in detail, laying a foundation for the preparation of high-quality In-based oxide target powders. The effects of ball milling, precipitation reaction temperature, and calcination treatment on the powder phase, particle size, particle shape, and crystallinity are explored. Moreover, the diffusion mechanism during the calcination process is analyzed. The results show that the ball milling process causes the In(OH)3 structure to transform from amorphous to crystalline, and the ball milling process can result in the agglomeration of precursor nanoparticles; the calcined powders also exhibit this behavior. The increase in the precipitation temperature of the precursor is beneficial for the refinement and homogenization of the In2O3 powder, but an abnormal grain growth occurs when the temperature is too high. In addition, at a calcination temperature of 350 °C, the In2O3 powder crystallization is incomplete, and In(OH)3 is observed in the powder. With the increase in the calcination temperature, the average grain size rapidly increases from 47.68 nm (700 °C) to 1250 nm (1400 °C). The dependence of the kinetic index of the growth process on the calcination temperature exhibits an opposite trend with respect to that of the growth rate. At a calcination temperature of 1050 °C, the kinetic index is the smallest (n = 3.96), and the activation energy increases suddenly, while the grain growth rate is the highest (the holding time increases from 1 to 7 h, and the grains grow by 61.64 %).

Stress-Controlled Creep–Fatigue of an Advanced Austenitic Stainless Steel at Elevated Temperatures

Creep–fatigue interaction occurs in many structural components of high-temperature systems operating under cyclic and steady-state service conditions, such as in nuclear power plants, aerospace, naval, and other industrial applications. Thus, understanding micromechanisms governing high-temperature creep–fatigue behavior is essential for safety and design considerations. In this work, stress-controlled creep–fatigue tests of advanced austenitic stainless steel (Alloy 709) were performed at a 400 MPa stress range and 750 °C with tensile hold times of 0, 60, 600, 1800, and 3600 s, followed by microstructural examinations. The creep–fatigue lifetime of the Alloy 709 was found to decrease with increasing hold time until reaching a saturation level where the number of cycles to failure did not exhibit a significant decrease. Softening behavior was observed at the beginning of the test, possibly due to the recovery of entangled dislocations and de-twining. In addition, hysteresis loops showed ratcheting behavior, although the mean stress was zero during creep–fatigue cycling, which was attributed to activity of partial dislocations. Microstructural examination of the fracture surfaces showed that fatigue failure dominated at small hold times where the cracks initiated at the surface of the sample. Larger creep cracks were found for longer hold times with a lower probability of dimpled cavities, indicating the dominance of creep deformation. The results were compared with other commonly used stainless steels, and plausible reasons for the observed responses were described.

Study on the Creep-Fatigue Interaction Behavior of 1Cr11Ni2W2MoV Steel

Abstract In order to investigate the creep-fatigue interaction of 1Cr11Ni2W2MoV steel, strain-controlled low-cycle fatigue tests were performed at various strain ranges with fully reversible cycle of triangular waveform at 500°C. In addition, different hold times were introduced at the maximum tensile strain to investigate the impact of creep damage on fatigue life. Fracture surfaces and axial section were evaluated in terms of crack growth behavior and propagation path. The creep-fatigue life decreased with increasing hold time. It was observed that cyclic softening effect intensified with tensile holding. Crack initiation and growth behavior changed in relation to hold time that exceeded 60 s at a strain range of 1.2 %, which led to premature failure. Under the present test conditions, a good description of fatigue life was provided by the model based on inelastic strain energy density.

Simulation modeling and optimization of bitumen –palm kernel oil blend for austempering of cast iron and steel

The study combines both simulation modeling and optimization of bitumen-palm kernel oil blend for austempering of cast iron and steel. Two independent factors namely austenitizing temperature (A) and holding time (H) were evaluated while five responses which includes ultimate tensile strength (u.t.s), hardness (h), impact strength (i), percentage elongation (e), percentage reduction in area (r.i.a) were evaluated. 3-D response surface and 2-D contour plots through response surface methods were used to estimate multi-response mathematical models. Desirability function approach provided by MINITAB 18 was used to determine the optimal settings of the response and factors after adequacy of the models to approximate the measured data had been established at 0.10 confidence level. From the result, optimum conditions for austenitizing temperature was 916.50C and 5 min while the predicted values of quenching hardness, ultimate tensile strength, impact strength, %elongation, %reduction in area were 1327.29MPa, 29.36J, 72.77%, 86.79% and 175.59HRC for 0.56%C-Steel; 1407.97MPa, 20.04J, 50.80%, 49.17% and 196.13 for 0.76%C-Steel; 1235.01MPa, 32.42J, 60.39%, 55.99% and 234.99HRC for ductile cast iron. Great improvement was seen in the steel performance after austempering process which gave rise to the conclusion that as the austempering time and holding time increases, that the mechanical properties of the steel were affected. Quenching of 0.56%C, 0.76%C-steel and ductile cast iron at the optimal settings using B-PKO saved one thousand naira (₦1000.00) showing 28.57% profit. The developed empirical models are recommended in some of the automobile and engineering industries during heat treatment operations so as to save time and energy.

Microstructural evolution and mechanical properties of Fe-0.14C-5Mn-1Al-Ce steel during intercritical annealing

The effects of intercritical annealing time on microstructure evolution and mechanical properties of a novel medium Mn steel (Fe-0.14C-5Mn-1Al-Ce) were investigated. The microstructure composed of lamellar ferrite and retained austenite (RA)/α’-martensite mixed phases after intercritical annealing. With the extension of intercritical annealing holding time, the volume fraction of RA first increases and then decreases, and RA is always formed at the high-angle grain boundaries of the ferrite. Both the product of Rm*A and the total elongation increase as the volume fraction of RA increases. The greater volume fraction of RA, the greater total elongation and Rm*A. The enrichment of carbon in RA was investigated by XRD and DICTRA. As intercritical annealing holding time increases, the carbon concentration in austenite decreases, while the change of the carbon concentration will affect the volume fraction of RA after intercritical annealing.

Interaction of austenite reversion with precipitation/dissolution during aging in a medium Mn steel alloyed with Cu, Ni and Al

Controlling the amount of retained austenite and precipitate particles allows for tailoring of mechanical properties in medium Mn steel alloyed with Cu, Ni and Al. The austenite reversion and precipitation/dissolution occur simultaneously during aging treatment at 550 °C being lower than Ac 1 . The degree of austenite transformation depends on the diffusion of austenite stabilizing elements (Mn, Cu and Ni), and the dissolution of the precipitate particles promotes the diffusion. Small angle neutron scattering (SANS) measurements were performed at the China Spallation Neutron Source (CSNS) to investigate the precipitation/dissolution behaviors. A large number of precipitate particles form at the aging time of 1 h, and then the volume fraction of the particles continuously decreases, and the average particle size has little change as holding time increases, indicating the dissolution of the precipitate particles. Atom probe tomography and transmission electron microscopy were used to study the type, composition and distribution of the precipitate particles. The particles contain Cu and NiAl-type precipitates, which have BCC and B2 structures, respectively. The characterization and modeling of austenite reversion kinetics indicate that austenite transformation is mainly controlled by the diffusion of Cu, which is promoted by the dissolution of Cu particles. This work offers significant insights towards an austenite-precipitate cooperative design for controlling the mechanical properties of the steel. • Austenite reversion occurs at aging temperature being lower than Ac 1 . • The diffusion of austenite stabilizing elements controls growth of austenite. • The dissolution of Cu particles facilitates the austenite transformation. • Austenite reversion and precipitation/dissolution control mechanical properties.