Zhefeng Zhang

Chinese Academy of Sciences | CAS

The effect of anisotropy on high‐cycle fatigue (HCF) property along the rolling direction (RD) and the transverse direction (TD) of a 7××× aluminum alloy super thick plate is mainly investigated in this study. The results show a similar microstructure at different thicknesses, and the HCF properties are close as well. The fatigue fracture morpholog...

The prediction of fatigue strength for metallic materials in a wide range of stress ratios is a crucial engineering challenge. To pursue a more accurate method, the dependence of fatigue strength on stress ratio for 35CrMo steel and other materials was investigated in detail. It was found that as the stress ratio increases, the damage mechanism cha...

A series of the second generation bi-crystal superalloys with specific misorientation grain boundaries (GBs) were prepared by the twin crystal seed method, and then their microstructure of GBs was characterized by means of scanning electron microscopy (SEM), meanwhile their tensile property was

ABSTRACT The microstructure and notch tensile fracture morphologies at different stress concentration factors of the low alloy steel 35CrMo for the head cover bolts of the pump turbine of a storage power station were investigated by electron backscatter diffraction microscopy and scanning electron microscopy. The effects of tempering temperature on...

The surface spinning strengthening (3S) mechanism and fatigue life extension mechanism of 316L stainless steel welded joint were systematically elucidated by microstructural analyses and mechanical tests. Results indicate that surface gradient hardening layer of approximately 1 mm is formed in the base material through grain fragmentation and defor...

The advantage of 3D printing—that is, additive manufacturing (AM) of structural materials—has been severely compromised by their disappointing fatigue properties1,2. Commonly, poor fatigue properties appear to result from the presence of microvoids induced by current printing process procedures3,4. Accordingly, the question that we pose is whether...

The strength and thermal conductivity of compacted graphite iron (CGI) are crucial performance indicators in its engineering application. The presence of graphite in CGI significantly influences the two properties. In the previous studies, graphite in CGI was often described using two-dimensional (2D) morphology. In this study, the three-dimensiona...

The ultimate tensile strength (UTS) of gray cast iron (GCI) could be affected by numerous parameters due to its complex microstructures. In order to further understand the UTS of GCI, it is necessary to evaluate the impact of various parameters. In this study, a UTS prediction method based on microstructure features and machine learning (ML) algori...

Cracking resistance is vital to the practical application of spring steels, which consists of fracture toughness ( K IC ) under the quasistatic loading condition and fatigue crack propagation (FCP) resistance under the cyclic loading condition. In the present study, the relation between the K IC /FCP resistance and microstructure of the 50CrMnSiVNb...

The trade-off relation between the strength and electrical conductivity (EC) limits the further application of Al wires in the automotive electronic wiring harnesses. In this work, an ultra-fine pure Al wire (UFPAW) with a diameter of around 0.2 mm was successfully prepared by the process of cold drawing → intermediate annealing → cold drawing. It...

The trade‐off relation between strength and plasticity is the bottleneck that limits the development of high‐strength and high‐plasticity Al–Cu alloys. Inspired from the influence of precipitate shape on the work‐hardening behavior of Al–Cu alloys, an Al–Cu–Zr–Sc alloy containing a mixed microstructure of spherical‐shaped Al3(Zr, Sc) phases and dis...

The assistance of alloying elements provides enormous opportunities for the discovery of high- performance face-centered cubic (FCC) medium-entropy alloys (MEAs). In this work, the influence of al- loying element Mo on the phase stability, stacking fault energy (SFE), deformation mechanisms, lattice distortion, and mechanical properties of (CoCrNi)...

To investigate the fatigue crack propagation (FCP) behaviors of high‐strength 7075 and 2024 Al alloys, FCP experiments are conducted for the two alloys at different aging states (underaged [UA], peak aging, and overaged). It is found that strength and plasticity are the main factors influencing the FCP. For 7075 Al alloy, the FCP curves almost coin...

Electrical contact materials are generally Ag- or Cu-based composites and play a critical role in ensuring the reliability and efficiency of electrical equipments and electronic instruments. The MAX (M is an early transition metal, A is an element from III or IV main groups, and X is carbon or/and nitrogen) phase ceramics display a unique combinati...

t is generally accepted that the mechanical properties of gray cast iron (GCI) can be enhanced by structure refinement, while this perhaps needs to be reconsidered to improve the fatigue properties treated by austempering technology. Although the maximum tensile strength can be up to 480 MPa for austempered gray iron (AGI) with finer bainite fabric...

The mollusk shells in Nature have evolved ingenious architectures and achieved outstanding mechanical properties, thereby demonstrating a potential for tissue engineering applications; nevertheless, despite a broad investigation of them for gaining inspiration towards guiding the design of man-made materials, the mollusk shells have rarely been exp...

Laser metal deposition (LMD) additive manufacturing has gained growing interest in the aerospace industry. Herein, a Ti–6.4Al–3.3Mo–1.6Zr–0.2Si (TC11) titanium alloy is produced by LMD. The inhomogeneity of multiscale grain morphology and mechanical properties are systematically investigated. The results indicate that the melting pool (MP) morpholo...

For solving the problem of fatigue life prediction on large-scale bolt, 35CrMo steel bolt was selected as the research object, and a simulated bolt component was proposed by the stress concentration factor as equivalent damage parameter. Then fatigue life of service bolt was estimated based on the fatigue comprehensive correction factor. The result...

Brittle" metallic glass (MG) usually fractures catastrophically in a shattering mode under macroscopic compression, because cleavage cracking of splitting that originates from extrinsic flaws dominates the failure of such alloys, which brings challenges for studying yield strength. Here we show that the plastic yielding behavior in a brittle Fe-bas...

Bioinspired nacre-like structures are effective in toughening materials, yet are difficult to construct in magnesium-ceramic systems. Here, a set of magnesium-MAX phase composites with nacre-like lamellar and brick-and-mortar architectures are fabricated by pressureless infiltration of the magnesium melt into ice-templated Ti3AlC2 ceramic scaffolds...

The nucleation of microstructural fatigue cracks in AISI 4340 steel is investigated. The pre‐electropolished specimen is employed for the observation of the very early stage of fatigue crack initiation correlated with the microstructure. It is found that there are precipitate‐free zones (PFZs) around the lath and packet boundary, and the strength o...

Herein, the effect of the aging state on the impact toughness of three typical wrought Al alloys (7075, 2024, and 6A01) is investigated. At room temperature, the fracture mode of the three aluminum alloys at different aging states is a ductile transgranular fracture. At low temperatures, high‐strength aluminum alloys exhibit a mixture fracture of t...

The high-temperature tensile properties, high-cycle fatigue properties and related damage mechanisms of vermicular graphite iron (VGI) with different microstructures at 500℃ were investigated. It is found that compared with ferritic VGI, pearlitic VGI has higher tensile strength and fatigue strength. The tensile strength shows a linear increasing t...

The hydrogen embrittlement (HE) behavior of a selective laser-melted (SLM) 316L austenitic stainless steel has been investigated by hydrogen charging experiments and slow strain rate tensile tests (SSRTs) at room temperature. The results revealed that compared to the samples without H, the ultimate tensile strength (UTS) and elongation (EL) of spec...

Refractory high-entropy alloy (RHEA) VNbMoTaW exhibits remarkably high strength in a much wide temperature range, whereas the brittle fracture behavior limits the applications. Here we show a significant size effect on the strength, plasticity and fracture behaviour of the VNbMoTaW RHEA. As sample size goes from millimeter to sub-micrometer scale,...

50CrMnSiVNb spring steel was quenched at 760, 820, 880, 940 and 990 ◦C to obtain different microstructures and nucleation rates of tempered carbides. The results show that for the QT-760 sample, the microstructure is mainly pearlite due to incomplete austenization. The coarse lamellar cementite significantly deteriorated the impact toughness. For o...

It is of particular interest to achieve high elastic recoverable strain in the electrical contact materials while maintaining good electrical conductivity and decent tensile strength. It remains a challenge, especially for bulk-sized metallic materials, as the electrical conductivity and elastic strain limit (or tensile strength) are often mutually...

The disastrous accident of the Titanic in 1912 occurred when the British ocean liner struck an iceberg and sank. Insufficient fracture resistance of the ship’s steel at low temperature ensured the ship’s demise. Thereafter, selection of materials with excellent cryogenic toughness became an important prerequisite for low-temperature, load-bearing a...

Microstructural evolutions of a cold-rolled CoCrFeMnNi high-entropy alloy (HEA) induced by electropulsing treatment at room temperature (RT-EPT) and liquid nitrogen (LN-EPT) temperature were investigated and compared. Finer recrystallized grains were obtained by LN-EPT compared to RT-EPT with the same discharge voltages. The recrystallization mecha...

Nanostructured materials are being actively developed, while it remains an open question how to rapidly scale them up to bulk engineering materials for broad industrial applications. This study propose an industrial approach to rapidly fabricate high-strength large-size nanostructured metal matrix composites and attempts to investigate and optimize...

The fatigue fracture mechanisms and the fatigue property evaluations of S355J2W steel butt-welded joints relieved welding residual stresses with and without welding reinforcement were systematically investigated by microstructure characterization and fatigue tests. Experimental results show that the complex evolution of microstructure at welded joi...

The eutectic cast Al–Si alloys with excellent high-temperature and casting performance are widely used in engine pistons. During frequent starts and stops, the thermo-mechanical fatigue (TMF) is the most important failure cause. Ultrasonic melt treatment (UT) was chosen to compare and investigate the influence of micro-structures on fatigue life an...

The typical microstructure of the laser melting deposition (LMD) additive-manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy (TC11) contains the heat-affected bands (HABs), the narrow bands (NBs) and the melting pools (MPs) that formed due to the reheating and superheating effects during the layer-by-layer manufacturing process. Characterization results...

It remains an intricate problem how to enhance low-cycle fatigue (LCF) performance, in the premise of guaranteeing a relatively high strength (or cyclic stress) which is vital to long-time service, for engineering components. The underlying cause of this puzzle is the lack of practical theory on cracking evolution/life prediction for LCF. In this s...

Considering the consumption of time and energy for the traditional heat treatment process, a new heat treatment method with high speed and low energy consumption has always been the direction of researchers. The microstructure and mechanical properties of engineering 316L stainless steel were measured under electropulsing treatment within 400 ns an...

In order to reveal the effects of cryogenic temperature on the relationship between mechanical properties and recrystallization percentage, the tensile mechanical behaviors of partial recrystallized copper have been investigated by tensile test at 293 K and 77 K, respectively. It is found the yield strength of copper maintains approximate linearity...

The development of multi-principal element alloys (MPEAs, also called as high- or medium-entropy alloys, HEAs/MEAs) provides tremendous possibilities for materials innovation. However, designing MPEAs with desirable mechanical properties confronts great challenges due to their vast composition space. In this work, we provide an essential criterion...

Bioinspired nacre-like structures are effective in toughening materials, yet are difficult to construct in Mg-ceramic systems. Here, a set of Mg-MAX phase composites with nacre-like lamellar and brick-and-mortar architectures were fabricated by pressureless infiltration of the Mg melt into ice-templated ceramic scaffolds. The structure and mechanic...

The effects of microstructures on the tensile properties, high-cycle fatigue properties and corresponding damage mechanism of compacted graphite iron (CGI) were investigated. The results show that with the increase of pearlite content, both the tensile strength and fatigue strength show an upward trend. Fatigue cracks usually initiate at the graphi...

Unidirectionally oriented architectures demonstrate a notable efficiency in enhancing the properties of macro-porous materials, yet are difficult to construct in a time- and cost-effective fashion. Here a facile approach was exploited for fabricating oriented macro-porous ceramic materials by employing natural graphite flakes as a fugitive material...

Orthopedic hybrid implants combining both titanium (Ti) and magnesium (Mg) have gained wide attraction nowadays. However, it still remains a huge challenge in the fabrication of Mg-Ti composites because of the different temperatures of Ti melting point and pure Mg volatilization point. In this study, we successfully fabricated a new Mg-Ti composite...

Ice-templating technique offers a viable means for constructing ordered macro-porous architectures in materials; nevertheless, it is generally limited by a low efficiency for fabrication, large difficulty for manipulation, along with the small dimension, and poor structural uniformity of ice-templated materials. Here, a new approach was exploited f...

Bioinspired architectures are effective in enhancing the mechanical properties of materials, yet are difficult to construct in metallic systems. The structure-property relationships of bioinspired metallic composites also remain unclear. Here, Mg-Ti composites were fabricated by pressureless infiltrating pure Mg melt into three-dimensional (3-D) pr...

During the selective laser melting (SLM) process of Ti6Al4V, a special structure can be formed with columnar prior β grains along the building direction and fully martensitic α′ within the β grain. To investigate the influence of such special structure on the fatigue crack growth (FCG) rate, Ti6Al4V specimens fabricated by SLM were heat‐treated at...

The Al–Mg–Si alloy wire for overhead transmission line is in thermal service due to the interaction between electric current and microstructure during power transmission, which could affect its microstructure and properties. At present, researchers generally use the traditional annealed-heated (A-H) treatment to simulate the thermal service state o...

For clinical applications, non-cytotoxicity and good bonding property of dental restorative materials are the most essential and important. The aim of this study was to evaluate the potential for clinical applications of two novel bioinspired nacre-like ceramic (yttria-stabilized zirconia)-polymer (polymethyl methacrylate) composites in terms of th...

The movement or dissociation of dislocations is significantly important for better understanding the plastic deformation mechanisms and mechanical properties of metals. It is commonly believed that a dislocation < 110 > /2 in Au is easy to dissociate into a pair of Shockley partial dislocations < 112 > /6 due to low stacking fault energy (SFE). Con...

Friction and wear performance is critical for dental materials which are inevitably subject to reciprocating friction against opposing teeth in applications. Here in-vitro friction and wear behavior of bioinspired ceramic-polymer composites, which possess nacre-like lamellar and brick-and-mortar architectures and resemble human teeth in their stiff...

In order to obtain the optimum fatigue performance, 35CrMo steel was processed by different heat treatment procedures. The microstructure, tensile properties, fatigue properties, and fatigue cracking mechanisms were compared and analyzed. The results show that fatigue strength and yield strength slowly increase at first and then rapidly decrease wi...

The mechanical properties and tensile deformation mechanism of Ti-6.5Al-3.5Mo-1.5Zr-0.25Si alloy (TC11) with different percentages of primary α phase (αp) were studied by conventional and interrupted tensile tests, respectively. The results show that the strength of TC11 alloy increases with the increase of the percentage of αp. During tensile defo...

The tensile properties, high-cycle fatigue (HCF) properties and corresponding fatigue fracture mechanism of compacted graphite iron (CGI) were investigated. It is found that the tensile strength, yield strength and fatigue strength of CGI decrease as the temperature increases. At 25°C, the fatigue cracks of CGI are mainly caused by local cleavage f...

The high‐cycle fatigue (HCF) experiments were carried out for different aging states to study the effects of the aging state and yield strength on the fatigue properties of a 6A01 Al alloy. The results show that the 6A01 Al alloy with the highest yield strength at a peak‐aging (PA) state can exhibit the highest fatigue strength in comparison with t...

Shot peening (SP) treatment is a common and useful method that can affect the fatigue life of metallic components. In this work, the high-cycle fatigue (HCF) lives of 50CrMnMoVNb spring steels with different SP intensities and conditions were investigated. Meanwhile, the differences in the microstructures and crack initiation sites were compared. T...

The corrosion fatigue performance of Al alloy components is crucial for their engineering applications. This study focuses on the corrosion fatigue properties of 7075 Al alloys in three different aging states, i.e. over-aging (OA), peak-aging (PA) and under-aging (UA) states. The results show that the fatigue damage mechanism of the Al alloy is gre...

Prior β grain evolution and phase transformation of selective laser melted (SLM) Ti6Al4V alloy after subtransus and supertransus solution heat treatments are investigated. A method based on the special angle grain boundaries (in the range of 15-55° and 70-85°) is proposed for a clear and straightforward description of the prior β mesostructure. Pos...

In the process of electric power transmission, the defects in the copper wire interact with the electrons which results in a thermal effect, accordingly, causing the changes of microstructure and properties of the copper wire. Herein, the evolution of microstructure, strength, and electrical conductivity of the oxygen‐free copper wires annealed at...

Aero-engine turbine disk is always subjected to cyclic loading at room and elevated temperatures. Therefore, as one of the typical high-temperature materials, selective laser melted (SLM) Inconel 718 superalloy was chosen to perform high-cycle fatigue tests at 25 °C, 450 °C and 650 °C and investigate the effect of temperature on fatigue damage mech...

An exponential strain-hardening (ESH) model for single phase metals was established and well verified by systematic experiments on Cu-Al alloys in an earlier study. In this report, several additional significant revelations will be documented for the tensile behaviors of several typical metals. Firstly, a unified interpretation of the well-known fi...

A simple exponential strain hardening model (ESH) has been developed in the framework of the Kocks-Mecking-Estrin formalism with a new microstructure based parameter that accounts for the effect of yield strength. The relevant parameters reflecting the effect of the composition (or dislocation annihilation distance) and the microstructure type (or...

It is generally accepted that anomalous slip (AS) takes place by hexagonal dislocation networks (HDNs) in body centered cubic (BCC) metals, but the role of the HDN formation process in AS has rarely been investigated so far. In this work, the critical yield conditions of the HDNs and isolated dislocations were first calculated, respectively, by mol...

Electropulsing treatment (EPT) in the liquid nitrogen (LN) circumstances, referred to as LN‐EPT, is utilized to regulate the microstructure and tensile properties of a cold‐rolled 316L austenitic stainless steel. The electropulsing effects between the samples treated in the ambient environment at room temperature (RT) and in the LN temperature are...

As the vulnerable component of diesel engine, cylinder head is subjected to the thermo-mechanical coupling loads more and more heavily. For establishing a simple and effective technology to evaluate the damage degree, a prediction method based on simulated component is developed in the present work. By the comparison of temperature and stress at me...

Fatigue fracture is the major threat to the railway axle, which can be avoided or delayed by surface strengthening. In this study, a low-carbon alloy axle steel with two states was treated by surface induction hardening and shot peening, respectively, to reveal the mechanism of fatigue property improvement by microstructure characterization, microh...

The microstructure, tensile and fatigue strengths of the high-strength 35CrMo steel with quenched and tempered (QT) and hot-rolled (HR) states were investigated. There is not a commonly linear relation between tensile and fatigue strengths, namely, the HR steel with higher tensile strength has lower fatigue strength, which is mainly attributed to m...

The high-cycle fatigue fracture behavior induced by different types of inclusions for high-strength steels was investigated. It is found that fatigue cracking of high carbon chromium bearing steel mainly originated from the interface between the matrix and the oxide inclusions while from the inside for nitride inclusions in the fatigue failure orig...

The aim of selective laser melting (SLM) technology is to obtain high quality workpieces through optimization of processing parameters. However, the defects and microstructures are simultaneously changed with the change of process parameters, so their effects are hard to discuss separately. To meet this challenge, 24 combinations of laser power and...

Tuning stacking fault energy (SFE) via alloying provides a robust protocol to manipulate deformation mechanism and consequently the mechanical properties of metallic materials. Mechanical behaviours of materials with small dimensions have received significant attention due to the increasing requirement of the miniaturisation and the development of...

Fatigue resistance is invariably critical for structural materials, but is rarely considered in the development of new bioinspired materials. Here the fatigue behavior and damage mechanisms of a nacre-like ceramic (yttria-stabilized zirconia) - polymer (polymethyl methacrylate) composite, which resembles human tooth enamel in its stiffness and hard...

Progress toward developing metal implants as permanent hard‐tissue substitutes requires both osteointegration to achieve load‐bearing support, and energy‐dissipation to prevent overload‐induced bone resorption. However, in existing implants these two properties can only be achieved separately. Optimized by natural evolution, tooth‐periodontal‐ligam...

High-temperature performance is a key factor to concern for the application of cast Al–Si alloys. The evolution of microstructures and mechanical properties of a multiphase Al–Si–Cu–Mg–Ni–Ce alloy during tension in a temperature range from 25 °C (ambient temperature) to 425 °C was investigated. The results show that the main strengthening precipita...

Optimizing the microstructure and mechanical properties of the selective laser melted (SLM) Ti6Al4V alloy is an important issue both in the scientific and engineering interests. In this study, the rapid hardening and softening of the SLM-Ti6Al4V alloy is realized due to the obvious evolution of microstructures during the electropulsing treatment (E...

Brittle materials, such as oxide glasses, are usually very sensitive to flaws, giving rise to a macroscopic fracture strength that is much lower than that predicted by theory. The same applies to bulk-metallic glasses (BMGs), with the important difference that these glasses can exhibit certain plastic strain prior to catastrophic failure. Here we c...

Natural fish scales demonstrate outstanding mechanical efficiency owing to their elaborate architectures and thereby may serve as ideal prototypes for the architectural design of man-made materials. Here bioinspired magnesium composites with fish-scale-like orthogonal plywood and double-Bouligand architectures were developed by pressureless infiltr...

Fatigue failure is the most common failure mode of structural materials. In this study, the high-cycle fatigue properties at different temperatures, fracture surface morphologies and corresponding damage mechanisms of a widely used vermicular graphite cast iron RuT450 were investigated. It is found that the fatigue strength values are 150 MPa, 143...

The fatigue damage and fracture of metallic glasses (MGs) were reported to be dominated by shear band. While there exist several reviews about the fatigue behavior of MGs, an overview that mainly focuses on shear bands under cyclic loading is urgent, and is of great importance for the understanding of fatigue mechanisms and properties. In this revi...