Cumulative Deformation Research Articles

A new explanation of Rolling Contact Fatigue in bearing steels based on multiscale models

Abstract Rolling Contact Fatigue (RCF) is harmful and inevitable to bearings and usually results in the initiation of subsurface damage. The root cause for this damage is the cumulative plastic deformation accentuated by carbides. This paper gives a new explanation of RCF based on multiscale models. The distribution and change law of subsurface shear stress in bearing steels was previously investigated by a finite element model. A two-phase atomic model of bcc-Fe and cementite was built. Ten alternating shear load cycles were designed to explore the mechanisms of the cyclic plastic accumulation when the atomic model was initially in the elastic, elastic- plastic and plastic stages, respectively. The results show that cyclic softening diversely occurs in all three types of stress responses. Severe cyclic shear deformation eventually leads to earlier cyclic softening and stress yield, which might be the micromechanism of plastic accumulation and RCF in bearing steels.

Investigation on Strain Characteristics and Fatigue Constitutive Model of Limestone under Osmotic Pressure and Cyclic Disturbance Coupling

The existing fatigue models are not sensitive to load cycles and do not consider the effect of osmotic pressure. To study the strain characteristics and fatigue constitutive model of limestone under osmotic pressure and cyclic disturbance coupling, 300 cycles of loading and unloading tests under different osmotic pressures were carried out and the evolution characteristics of irreversible accumulative deformation curve were analyzed. Then, an improved Nishihara fatigue model was established based on the theoretical results of rheological model by introducing the nonlinear function into Nishihara model. The results show that the irreversible cumulative deformation under different osmotic pressures experiences three evolutionary processes of initial deformation stage, stable deformation stage, and accelerated deformation stage with increasing cycle indexes, showing the typical fatigue deformation characteristics. The axial deformation at initial deformation stage increases significantly, the stable deformation stage shows approximately linear growth and accounts for 40% to 73% of total cycle indexes, and the accelerated deformation stage shows a sudden increase indicating the overall instability of limestone. The nonlinear function is introduced into the Nishihara fatigue model based on rheological theory, and a fatigue deformation model that can reflect the entire process of irreversible accumulative deformation curve is established. The physical meanings of model parameters are discussed, and the relationships between model parameters and cycle indexes are inverted. The model parameters have good convergence and verify the rationality and applicability of the fatigue constitutive model based on experimental data. The results have reference value for revealing the fatigue characteristics of rock under osmotic-cyclic stress coupling.

Time-Series Analysis and Prediction of Surface Deformation in the Jinchuan Mining Area, Gansu Province, by Using InSAR and CNN–PhLSTM Network

Surface deformation poses a great threat to the safety of Jinchuan mining area production activities. At present, the spatio-temporal evolution law and mechanism of surface deformation in the Jinchuan mining area are unclear, and it is difficult to obtain reliable prediction results using the existing spatio-temporal prediction methods due to the lack of model parameters or relevant data. To solve these problems, this study proposes a new unified convolutional neural network with peephole long short-term memory (CNN-PhLSTM). Small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology was used to obtain the spatio-temporal evolution characteristics of surface deformation in the period of 2014–2021. Time series InSAR deformation data are merged into a unified network model in series with a time-distributed CNN segmentation and stacked PhLSTM. The InSAR measurement results are shown to be reliable by comparison and verification with the benchmark and InSAR results of different orbits. The proposed CNN-PhLSTM model was evaluated by mean absolute error and structural similarity (SSIM) evaluation indexes, and was compared with support vector regression (SVR), multilayer perceptron (MLP) and CNN-LSTM models. The results show three continuous subsidence areas, namely the Longshou, second western and third eastern mining areas. The cumulative surface deformation continued to increase from 2014 to 2021. Faults and lithology control the spatial distribution of surface deformation in the Jinchuan mining area. The prediction results demonstrate that the surface deformation range will continue to expand and that time-series surface deformation will show a slow deceleration trend in the next two years.

Effect and mechanism of cold rolling and aging process on microstructure and properties of columnar grain C70250 copper alloy

The C70250 copper alloy billet produced by continuous directional solidification technology was cold rolled and aged. The influences of cold rolling deformation and aging process on the microstructure, mechanical and electrical properties of the alloy were investigated, and the mechanism was also revealed. Our results indicate that the peak aging tensile strength and electrical conductivity of the C70250 copper alloy gradually increase with the increase of cold rolling deformation amounts. When cumulative cold deformation amount reaches 95%, the aging treatment of 450 °C and 1 h was the optimal heat treatment process, the yield strength of the alloy is 720 MPa, the tensile strength is 758 MPa and the conductivity is 52.5% IACS under this condition. Compared with the traditional preparation process, the comprehensive properties are significantly improved. Large cold rolling reduction makes the columnar grain structure of C70250 copper alloy produce uniform shear deformation, promotes the uniform precipitation of Ni2Si phase in the aging process, leading to finer precipitates and more uniform distribution in the peak aging alloy. Dislocation slip is hindered, grain boundary migration capacity is reduced and the strength of the alloy is improved. The parallel shear band produced by large deformation cold rolling cuts the matrix evenly, which not only leads to the transformation of columnar grain structure into fiber strip structure, reduces the transverse grain boundary density, but also accelerates the precipitation of solute atoms, reduces the influence of solute atoms on electron scattering. Besides, the long fiber structure provides a channel for free electron transport, greatly reduces the barrier of electron transmission and improves the conductivity of the alloy.

Review of the SBAS InSAR Time-series algorithms, applications, and challenges

In the past 30 years, the small baseline subset (SBAS) InSAR time-series technique has emerged as an essential tool for measuring slow surface displacement and estimating geophysical parameters. Because of its ability to monitor large-scale deformation with millimeter accuracy, the SBAS method has been widely used in various geodetic fields, such as ground subsidence, landslides, and seismic activity. The obtained long-term time-series cumulative deformation is vital for studying the deformation mechanism. This article reviews the algorithms, applications, and challenges of the SBAS method. First, we recall the fundamental principle and analyze the shortcomings of the traditional SBAS algorithm, which provides a basic framework for the following improved time series methods. Second, we classify the current improved SBAS techniques from different perspectives: solving the ill-posed equation, increasing the density of high-coherence points, improving the accuracy of monitoring deformation and measuring the multi-dimensional deformation. Third, we summarize the application of the SBAS method in monitoring ground subsidence, permafrost degradation, glacier movement, volcanic activity, landslides, and seismic activity. Finally, we discuss the difficulties faced by the SBAS method and explore its future development direction.

Research on Shear Behavior of Sand–Structure Interface Based on Monotonic and Cyclic Tests

In order to study the shear behavior of the interface between sand and structure, a series of shear tests were carried out using an HJ-1 ring shear apparatus (Nanjing, China). First, through the monotonic shear tests, the loose sand and dense sand were sheared at the steel interface with different roughnesses. The results showed that when the interface was relatively smooth, the shear stress–shear displacement curves of loose sand and dense sand both exhibit strain hardening characteristics. When the interface was rough, the dense sand showed strain softening. The initial shear stiffness of the sand–steel interface increased with the increase in normal stress, interface roughness, or sand relative density. Then, considering the influence of initial shear stress, through the cyclic shear test, this work analyzed the shape of the loading and unloading curves and the development law of cumulative normal deformation, and discussed the change of loading and unloading shear stiffness under different stress level amplitudes and the residual deformation generated during the cycle. The research results showed that loose sand and dense sand generally shrunk in volume during the cycle. The initial loading process was similar to the case of static loading. In the later dynamic loading process, the shear shrinkage per cycle was relatively small and continued to develop. Additionally, it was found that the unloading stiffness of the sand–steel interface is always greater than the initial loading stiffness. As the number of cycles increases, the loading stiffness increases, and it may eventually approach the unloading stiffness.

Horizontal cyclic response of bucket caisson for offshore wind turbines in over-consolidated clay

Compared with pile foundations, bucket caisson has the advantages of convenient installation and recyclability, and is more suitable as foundation for offshore wind turbines. Horizontal cyclic response is very important for the stability analysis of bucket caisson as it suffers long-term wave loadings in service period. This study presents the results of a series of 1 g model tests under horizontal cyclic loadings in over-consolidated clay. The cumulative deformation, stiffness changes and rotation centre variation of caisson model were discussed in detail. Test results indicated that the horizontal displacement of caisson model in over-consolidated clay accumulated with the increase of cyclic number and horizontal loadings. However, the increase of horizontal displacement gradually decreases for each cycle. Based on this, an empirical equation between Tb and ζb was proposed to predict the accumulated rotation of bucket caisson in over-consolidated clay. The position of rotation centre for caisson model in this study had the tendency to move up gradually. When the caisson model was under fatigue limit state (ζb=0.4), the type of rotation changes from deep to shallow certre. Under the state of ULS/1.35 (ζb=0.6), the type of rotation is always shallow centre during the whole cyclic loadings. The unloading stiffness of caisson model decreases logarithmically and tends to be stable with the increase of loading cycles. Due to the change of unloading stiffness, the system natural frequency of bucket caisson is reduced by about 37%. This study can provide theoretical basis for the design of bucket caisson as offshore wind power foundation in over-consolidated clay.

Microstructure Evolution of AS41 Magnesium Alloy in ECAP

ECAP is a continuous multi-pass extrusion process that enables the specimen to obtain considerable cumulative deformation to refine the grain. In this paper, ECAP was used to deform AS41 magnesium alloy at 350°C, and the microstructure was observed and analyzed. The results show that the ECAP process has excellent effect on grain refinement and uniform microstructure. The grain size of AS41 decreases from 200μm to 20μm, and the microstructure is more uniform than that of as-cast sample. The reason is that the original grain is broken and refined under the action of shear force, and dynamic recrystallization occurs at the same time, resulting in small recrystallized grains. The Mg2Si particles were redistributed during ECAP and uniformly distributed in the crystal in rod shape.

Assembly variation analysis of the non-rigid assembly with a deformation gradient model

PurposeThis paper aims to develop a mathematical method to analyze the assembly variation of the non-rigid assembly, considering the manufacturing variations and the deformation variations of the non-rigid parts during the assembly process.Design/methodology/approachFirst, this paper proposes a deformation gradient model, which represents the deformation variations during the assembly process by considering the forces and the self-weight of the non-rigid parts. Second, the developed deformation gradient models from the assembly process are integrated into the homogenous transformation matrix to model the deformation variations and manufacturing variations of the deformed non-rigid part. Finally, a mathematical model to analyze the assembly variation propagation is developed to predict the dimensional and geometrical variations due to the manufacturing variations and the deformation variations during the assembly process.FindingsThrough the case study with a crosshead non-rigid assembly, the results indicate that during the assembly process, the individual deformation values of the non-rigid parts are small. However, the cumulative deformation variations of all the non-rigid parts and the manufacturing variations present a target value (w) of −0.2837 mm as compared to a target value of −0.3995 mm when the assembly is assumed to be rigid. The difference in the target values indicates that the influence of the non-rigid part deformation variations during the assembly process on the mechanical assembly accuracy cannot be ignored.Originality/valueIn this paper, a deformation gradient model is proposed to obtain the deformation variations of non-rigid parts during the assembly process. The small deformation variation, which is often modeled using a finite-element method in the existing works, is modeled using the proposed deformation gradient model and integrated into the nominal dimensions. Using the deformation gradient models, the non-rigid part deformation variations can be computed and the accumulated deformation variation can be easily obtained. The assembly variation propagation model is developed to predict the accuracy of the non-rigid assembly by integrating the deformation gradient models into the homogeneous transformation matrix.

Fault Activation in Central Mongolia during the Holocene: Results of Study of the Mogod Earthquake Ruptures

Abstract —In order to determine the seismotectonic activity of faults in the Holocene, we performed trench studies of the ruptures produced by the catastrophic Mogod earthquake (5 January 1967, M = 7.5–7.8, I0 = 9–10) in the junction zone of the N–S striking Hulzhin Gol fault and the NW striking Tullet fault. Paleoseismic interpretation of seismic-deformation sections and radiocarbon dating of the samples allowed determining the kinematics and obtaining, for the first time, the absolute ages of paleoevents preceding the Mogod earthquake. Analysis of the tectonic conditions for realization of earthquake sources has shed light on the complex structure of ruptures in the area of the Mogod earthquake epicenter, within which three segments differing in the displacement amplitudes and kinematics have been identified. The research data indicate the repeated activation of the Tulet and Hulzhin Gol faults in the Late Pleistocene–Holocene. The absolute age of the latest activation is 596–994 AD for the Tulet fault and 11,379–6235 BC for the Hulzhin Gol fault. The cumulative deformation from paleoearthquakes in the trench sections in the Tulet fault zone points to at least two displacements of thrust kinematics, with the latest of them having an amplitude of 2.8 m. The paleoearthquake in the Hulzhin Gol fault zone is characterized by the presence of lateral slip. The amplitudes of deformations attest to earlier earthquakes similar in energy to the 1967 Mogod event or even stronger in the fault node. The obtained data on the timing of these earthquakes and the amplitudes of the accompanying displacements made it possible to estimate slip rates along the faults: 0.2–0.3 m/kyr horizontal-slip rates on the Hulzhin Gol fault and 0.5–0.7 m/kyr vertical-slip rates on the Tulet fault.

Low-cycle fatigue life evaluation of buckling-restrained braces based on cumulative plastic deformation curves

To quantitatively evaluate the low-cycle fatigue life of buckling-restrained braces (BRBs), an evaluation method for BRBs based on the combination of the CPD curves and CPD measurement meter (CMM) is established herein. The difference between two CPD curves (i.e., the CPD curves under constant strain amplitude loading history (C-CPD) and under random strain amplitude loading history (R-CPD)), and their selection criteria to evaluate the low-cycle fatigue life of BRBs are discussed. An example under the variable strain amplitude (VSA) loading history and an example under the multiple earthquakes are carried out. Finally, the CPD limit values of BRBs in the ANSI/AISC 341-10 and FEMA-450 are discussed by statistical analysis of the test results of BRBs. The analysis results show that the C-CPD curve can be used to evaluate the low-cycle fatigue life of BRBs under the VSA loading, and the R-CPD curve can be used to evaluate the low-cycle fatigue life of BRBs under the multiple earthquakes. The degree of reliability of the current CPD limit value is not enough. A CPD limit curve is recommended in this study to quantify the low-cycle fatigue performance of BRBs.

Seismic behavior of high-strength concrete-filled square steel tube columns reinforced with ultrahigh-strength reinforcing bars

This paper investigated the seismic behavior of high-strength concrete-filled square steel tube columns reinforced with ultrahigh-strength reinforcing bars. Three full-scale specimens with different amounts of ultrahigh-strength longitudinal reinforcing bars under a high axial load ratio and cyclic lateral load were tested. The test results demonstrate that the existence of ultrahigh-strength longitudinal reinforcing bars had a significant influence on the seismic behavior of high-strength concrete-filled steel tube columns. Compared with conventional concrete-filled steel tube (CFT) columns, the deformation capacity, bearing capacity and cumulative energy dissipation of these innovative CFT columns are greatly improved, and the cumulative damage and plastic deformation of the specimens decreased with the introduction of steel bars. A calculation model based on AISC360-16 using the superposition method was proposed and verified to evaluate the compressive-flexural strength of the specimen.

Influence on mechanical behaviors considering construction hosting process of large-scale steel structure

In the design of large-scale steel structure, the design calculation of the structure is usually based on the service state. But in the process of steel structure construction, the displacement and stress produced in the construction process cannot be completely consistent with that in the design state. With the progress of construction process, the deformation and stress caused by self-weight and construction load gradually accumulate until the structure is formed, which will produce construction error relative to the design state. In this paper, FEM method was used to simulate the construction process of the steel grid roof of the theater in the Beijing Sub Center Theater project, and the influence of the accumulated deformation and stress on the mechanical properties of the structure during the construction process was analyzed. The results show that the cumulative deformation and stress in the construction process have a great influence on the final deformation and stress distribution of the structure. The maximum vertical displacement in the actual construction state is 599.6% of that in the design state, and the maximum stress is 119.7% of that in the design state. This will lead to the difference between the construction-completed structure and the design structure, which makes the design result dangerous. The measures to optimize the construction process were also given in this paper, which provides guidance for the construction process of large-scale steel structure.

Energy dissipation capacity for waffle-flat-plate structures subjected to bi-directional seismic loadings

The seismic capacity of buildings is usually studied through separate analysis of two orthogonal directions, then combined using empirical rules. Nevertheless, the three-dimensional nature of seismic action gives rise to interaction among its different components, especially the two horizontal ones, which can cause substantial discrepancy between the actual 3D response and the one obtained by combining uniaxial responses. The present study addresses this problem for waffle-flat-plate (WFP) structures with an irregular layout of columns from the standpoint of energy dissipation capacity. A portion of a WFP prototype structure that was built in Laboratory was subjected, simultaneously, to two horizontal components of a far-field seismic record upon a shake-table. Several shakings of increasing intensity were applied until the collapse of the structure. Afterwards, a numerical model of the specimen was developed and validated with the experimental results. The numerical model was subjected to several sets of ground motions having diverse ratios of energy input from the horizontal components. When the total energy dissipated by the structure through cumulative plastic deformations until failure was obtained for each set of accelerograms, a fairly stable quantity was found to be concentrated within a narrow range of values. Moreover, the specimen subjected to bi-directional seismic loading showed a higher ultimate energy dissipation capacity than under uni-directional loadings.

Hysteretic performance of all-steel assembled double-cores buckling-restrained braces using Q195 low-yield core

This paper focuses on the hysteretic behavior of a proposed all-steel assembled double-cores buckling-restrained braces (DCBRB). The DCBRB employs an I-shaped steel and two channels to resist the global instability of the brace and hence to force the double-cores into high-order buckling mode for the purpose of energy dissipation. Six DCBRB specimens were fabricated, where both Q195 low-yield core and Q235B core were concerned for comparison. The quasi-static cyclic loading was conducted on the DCBRB specimens to investigate the failure modes, as well as the hysteretic behavior from different perspectives, such as hysteretic curves, skeleton curves, compressive strength adjustment factor, energy dissipation capacity and plastic deformation performance. The experimental results demonstrate that the insufficient constraining of the external restraining member could cause the global instability of the buckling-restrained braces. The specimens exhibited great and stable hysteretic responses until the axial strains of cores researched 1.5%. Finally, the cumulative plastic deformation capacities were greater than 300 for all specimens. The finite element models were established to further investigate the influence of constraint ratio and core's width-to-thickness ratio on the hysteretic behavior of the DCBRBs. The numerical results reveal that better global stability is expected to be obtained with a larger constraint ratio ζ, and the limit value of ζ avoiding the global buckling almost increases linearly with the increase of core's width-to-thickness ratio.

Calculation Method of Underground Passage Excavation on Interactive Effects among Pipe-Roof, Steel Bracing and Foundation Soil

The ultra-shallow buried excavation technology, utilizing pipe-roof steel arches as main supporting structure, has broad application prospects. Current mainstream pipe-roof design schemes often adopt simple beam theory or engineering analogy methods, which do not take into account the cumulative deformation and have high engineering disaster risk. Based on the beam Winkler model of elastic foundation, this paper studies the method on interactive effects among pipe-roof, steel bracing and foundation soil. The calculation model of the ultra-shallow buried pipe-roof and steel bracing is established with theoretical derivation. And a new supporting design method of ultra-shallow buried excavation under interactive effects is proposed. Firstly, an optimal method for determining the elasticity coefficient of steel arch and foundation soil is put forward on interactive effects among pipe-roof, steel bracing and foundation. Secondly, considering the enhancement effect of concrete wall, a procedure of determining the elasticity coefficient of fulcrum is described. That is, the first steel arch, which is adjacent to underground passage tunnel face, returns to the 1.5H (H is the height of the hole) range as an enhanced transition section, and the elasticity coefficient of fulcrum varies linearly with its position. Furthermore, the key issue is the deformation of the inlet section increases to a stable level in a certain range, while the ground settlement does not exceed the threshold. The selection of pipe-roof is controlled by calculated deformation. If the deformation meets the requirements, the internal force will be far enough to meet the requirements. Only two sections need to be considered when calculating the ultra-shallow buried underground passage, the entrances 2.0H and the central across section. Finally, the accuracy of the interactive effects calculated method is validated by using the measured data of a practical example.

QUASI-STATIC CYCLIC TESTS ON THE HYSTERETIC BEHAVIOR OF BUCKLING-RESTRAINED BRACES WITH A T-SECTION CORE

An all-steel assembled buckling-restrained brace is proposed, in which both the core and the restraining members are made of section-steel. The brace has the advantages of assembly, replaceable core, easy fabrication, low cost and can be used for strengthening existing members. The steel core is composed of two angle steels and stiffening plates to form a T-shaped section. The restraining members are formed by bolting plates and angle steels through mat strips. Quasi-static cyclic tests for six specimens were carried out to investigate the hysteretic performance, seismic performance and failure modes. The effects of adding filler plates in the core, the gap between the core and the restraining members, the spacing between the two angle steels of the core, and the stopper configuration on the hysteretic performance were analyzed. The results show that the actual performance of the brace was basically consistent with the design performance. The brace specimens exhibited stable hysteretic performance. Adding filler plates in the middle of the core shows little influence on the hysteresis performance. An excessive gap between the core and the restraining member and excessive spacing between the two steel angles of the core reduced the hysteresis performance. The hysteretic performance of the braces with middle stoppers were better than the brace with end stoppers. The analysis of the seismic performance of the specimens shows that the braces have satisfactory ductility and cumulative plastic deformation capacity, which can be used as dampers in structures. By analyzing the failure modes, the stress concentration of the welding at the end of the stiffening plates will make the failure position move from the yielding segment to the stop of the weld. The middle stopper of the core can reduce the adverse effects of friction.

Creep Properties of Expansive Soils under Triaxial Drained Conditions and its Nonlinear Constitutive Model

The creep behaviors of expansive soils play an important role in landslide prediction and long-term stability analysis. In this paper, triaxial drained compression creep tests of expansive soils were conducted on the improved stress-controlled triaxial apparatus. The test results show that only transient deformation and attenuation creep occur with low deviator stress, and the increment of axial strain increases exponentially with deviator stress increasing; while deviator stress reaches a certain value, attenuation creep, steady creep and accelerated creep all occur in a creep curve. Meanwhile, the volumetric strain presents the shear shrinkage characteristic at the initial stage of loading, and the shear shrinkage is small. With the extension of loading time, the volumetric strain gradually varies from shear contraction to dilatancy. When entering the accelerated creep stage, the development rate of volumetric strain increases sharply. Besides, isochronous stress-strain curves of expansive soils indicate that their creep process possesses nonlinear characteristics, and the nonlinear degree is related to creep time and stress level. Imitating the empirical formula of cyclic cumulative deformation of clay, a new nonlinear creep model is presented, which may well describe the creep property of expansive soils. Furthermore, critical failure stress could be obtained based on the proposed creep model. The ratio of the critical failure stress to conventional shear failure stress ranges from 70% to 80%, with average of 75.56%, therefore, critical failure stress may be estimated by conventional triaxial tests with the margin of error 5.5% within.

25,000 Years long seismic cycle in a slow deforming continental region of Mongolia

The spatial distribution of large earthquakes in slowly deforming continental regions (SDCR) is poorly documented and, thus, has often been deemed to be random. Unlike in high strain regions, where seismic activity concentrates along major active faults, earthquakes in SDCR may seem to occur more erratically in space and time. This questions classical fault behavior models, posing paramount issues for seismic hazard assessment. Here, we investigate the M7, 1967, Mogod earthquake in Mongolia, a region recognized as a SDCR. Despite the absence of visible cumulative deformation at the ground surface, we found evidence for at least 3 surface rupturing earthquakes during the last 50,000 years, associated with a slip-rate of 0.06 ± 0.01 mm/year. These results show that in SDCR, like in faster deforming regions, deformation localizes on specific structures. However, the excessive length of return time for large earthquakes along these structures makes it more difficult to recognize earthquake series, and could conversely lead to the misconception that in SDCR earthquakes would be randomly located. Thus, our result emphasizes the need for systematic appraisal of the potential seismogenic structures in SDCR in order to lower the uncertainties associated with the seismogenic sources in seismic hazard models.

Effects of annealing on mechanical properties and degradation behavior of biodegradable JDBM magnesium alloy wires

Mg–Nd–Zn–Zr magnesium alloy (JDBM) has been studied widely as biodegradable medical material. To process high quality JDBM wires, effects of annealing on the mechanical properties and degradation behavior after drawing were studied by microscopic observations, tensile and immersion tests. The as-extruded wires with a diameter of 3 mm could be drawn up to 9 passes without annealing until 125% cumulative drawing deformation. Complete recrystallization occurred after annealing at 325 °C for 30 min, 350 °C for 5 min or 450 °C for 3 min, respectively. Room temperature tensile tests and simulated body fluid immersion tests showed that annealing at slightly elevated temperature for short time could obtain better properties due to the finer grain size and more dispersive distribution of precipitates. For this study, annealing at 350 °C for 5 min is the best parameters which can be utilized to further fabricate fine wires.