Yanzhong Tian

Northeastern University (Shenyang, China) | NEU · Key Laboratory for Anisotropy and Texture of Materials

Fully recrystallized ultrafine-grained (UFG) pure Cu specimens were fabricated by high-pressure torsion (HPT) and controlled annealing. The recrystallized UFG Cu with a minimum mean grain size of 0.51 μm showed high yield strength, good ductility, obvious yield drop and large Lüders strain during tensile test. The mechanical behavior of the Cu spec...

Although Cu was studied extensively, the Hall-Petch relationship was mainly reported in the coarse-grained regime. In this work, fully recrystallized Cu specimens with a wide grain size regime of 0.51~14.93 um manifest a two-stage Hall-Petch relationship. There is a critical grain size of 3 um that divides stages I and II where the Hall-Petch slope...

Strength and hardness of metallic materials are reported to correlate in a specified form. Among various equations, yield strength is generally converted from Vickers hardness (HV) via a three‐time relation due to the simple and nondestructive nature of hardness testing. Herein, a through literature review is made and data of strength and HV for fa...

The yield strength of 316LN stainless steel is always insufficient due to the single-phase austenitic structure. We processed bulky specimens with recrystallized ultrafine-grained microstructure by cold rolling and annealing treatments. The specimens are strong and ductile at 293 K as a result of dislocation-dominated plastic deformation process. I...

Grain refinement increases yield strength, but usually at the cost of ductility reduction. In the present work, we explored the strategy of grain refinement and composition tuning in CoCrNi alloys to optimize mechanical properties. Grain refinement was found to strongly suppress deformation-induced martensitic transformation in metastable CoCrNi al...

A Cu-10wt%Fe composite was prepared through hot-pressed sintering, and the material was subsequently solution treated. The hot-pressed sintered and solution treated materials were rolled and aged. The precipitation behavior and performance changes were systematically studied by using scanning electron microscopy and transmission electron microscopy...

Impacts of Mn alloying on lattice stabilities, magnetic properties, electronic structures of the bcc and fcc phases and the fcc→bcc phase transition in Fe 16−x Mn x (x = 0, 1 and 2) alloys are studied by first-principles calculations. Results show that the doped Mn atom prefers ferromagnetic and antiferromagnetic interaction with the host Fe atoms...

CoCrNi alloys exhibit excellent strength and ductility. In this work, the CoCrNiV multi-principal alloy with single-phase fine grained (FG) structure was prepared by rolling and heat treatment. The characteristics of deformation microstructures and mechanical properties were systematically investigated by scanning electron microscope (SEM) and tran...

The Fe macrosegregation during casting and the limited sample size of the traditional powder metallurgy methods are challenges for the application of Cu-Fe composite. In this work, a powder rolling strategy is developed to fabricate fully dense Cu-10Fe billet by consolidating pure Cu and Fe powders. This method can solve the above problems. The mic...

Equiatomic CoCrNi medium-entropy alloys exhibit superior strength and ductility. In this work, a non-equiatomic CoCrNi alloy with low stacking fault energy was designed, and different fractions of V were added to control the stacking fault energy and lattice distortion. Mechanical properties were evaluated by tensile tests, and deformation microstr...

Properties of grain boundaries are pronouncedly influenced by alien elemental segregation. Synergistic effect of co-segregation behavior on mechanical properties of Mg {101̅2} twin grain boundary was systematically investigated with first-principles calculations. Ten elements (Ni, Mn, Zn, Al, Ag, Ti, Li, Zr, Y, Ca) for single segregation and four s...

The application of immiscible Cu-Fe composite was limited due to the severe Fe macrosegregation and low electrical conductivity. In this work, bulk Cu-10Fe composite was prepared by powder rolling strategy and further cold rolled to foils. The composition distribution, microstructure evolution, electrical property and mechanical property were studi...

Nanostructured metallic materials often lack sufficient work-hardening capability and suffer premature necking during tensile loading. In this study, intense rolling strain was applied to process nanocrystalline CuAg sheet, and aging treatment was designed to further tailor the microstructure and properties. Features of grains, Ag precipitates and...

High-density and nanosized deformation twins in face-centered cubic (fcc) materials can effectively improve the combination of strength and ductility. However, the microscopic dislocation mechanisms enabling a high twinnability remain elusive. Twinning usually occurs via continuous nucleation and gliding of twinning partial dislocations on consecut...

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...

Advanced materials with superior comprehensive mechanical properties are strongly desired, but it has long been a challenge to achieve high ductility in high-strength materials. Here, we proposed a new V0.5Cr0.5CoNi medium-entropy alloy (MEA) with a face-centered cubic/hexagonal close-packed (FCC/HCP) dual-phase ultrafine-grained (UFG) architecture...

In this study, the effect of nitrogen on microstructural evolution and Charpy impact energy of CoCrFeMnNi high-entropy alloy (HEA) was investigated, and the corresponding fracture mechanism was revealed. Nitrogen atoms fully dissolved into the matrix and markedly increased the Charpy impact energy of 0.52N alloy. The fracture morphologies of the 0N...

The present work reports a tri–phase hierarchical lamellar structure to tailor the ultra–high yield strength and high ductility balance in a novel Si–Al added medium Mn lightweight TRIP/TWIP steel. The warm–rolled sample was subjected to small cold rolling and low–temperature tempering to obtain the nano–scale twins and martensitic laths in the aus...

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...

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...

Low ductility has always been a drawback for nanostructured materials. In this study, we applied a low-temperature annealing process on a cold rolled Al-8.1Mg-0.15Zr alloy with supersaturated state. It is found that the uniform elongation of the rolled specimen was improved by 124% after a low-temperature annealing treatment at 333 K, while an enha...

Understanding the atomistic details on microstructures and phase transformation mechanisms is essential to tailor the performances of materials. Refractory body-centered cubic (bcc) high-entropy alloys (HEAs) are considered as promising candidates for future applications in the high-temperature, superelasticity, and superconductivity fields. The cl...

Ceramic coatings were prepared by plasma electrolytic oxidation (PEO) on four different surface roughness’ of Ti-6Al-4V alloys. The effects of substrate roughness on the microstructure and fatigue behavior were investigated. Microstructural characterization was carried out by scanning electron microscopy (SEM) and a laser scanning confocal microsco...

Dense networks of deformation twins endow metals and alloys with unprecedented mechanical properties. However, the formation mechanism of these hierarchical twin structures remains under debate, especially their relations with the imperfect nature of twin boundaries (TBs). Here, we investigate the intrinsic deformability of defective TBs in face-ce...

Metallic materials can be strengthened by various kinds of plastic deformation strategies. However, the deformed materials suffer poor ductility and thermal stability due to the high-density defects. In this work, we prepared fully recrystallized ultrafine-grained (UFG) 1%C-CoCrFeMnNi high-entropy alloy (C-HEA) through cold rolling and annealing pr...

3D printing of high-strength alloys enables efficient manufacturing of complex metallic components. Yet, the as-built parts are often characterized by unsatisfied ductility due to micro-defects, requiring additional heat treatment to optimize the structure before in-site applications. The post heat-processing, however, often changes the shape of th...

Two different types of shear bands generate in ultrafine-grained (UFG) CoCrFeMnNi high-entropy alloys deformed at 77 K, i.e. commonly-observed low angle grain boundary (LAGB) type and unusual twin-coupled type. Twin-coupled shear bands exhibit a misorientation of 56–67° with the matrix, in contrast to the LAGB shear band with a misorientation of 6–...

Combined theoretical and experimental efforts are put forward to study the critical factors influencing deformation mode transitions in face-centered cubic materials. We revisit the empirical relationship between the stacking fault energy (SFE) and the prevalent deformation mechanism. With ab initio calculated SFE, we establish the critical boundar...

Cu-Cr-Zr alloy can be strengthened by modulating the aging process. In this work, the effect of two-stage aging on the properties of Cu-Cr-Zr solid solution was studied. Hardness, tensile properties and electrical properties were tested, and the microstructures were examined by transmission electron microscope. The results show that pre-aging can f...

A comprehensive investigation into dry sliding wear and associated evolutions of subsurface microstructure and nano-mechanical properties of a bulk nano-grained Ti6Al4V alloy (NG-Ti6Al4V) was conducted. Comparing with its coarse-grained counterpart (CG-Ti6Al4V), NG-Ti6Al4V always exhibited lower friction coefficient and greater wear resistance in a...

Laminated composite consisting of 304L stainless steel and CoCrFeMnNi high-entropy alloy (HEA) are prepared by additive manufacturing technology. Apparent element diffusion was activated during the additive manufacturing process, but no new phase was detected near the interface between 304L and HEA. The microstructure was modulated by post treatmen...

In this study, the effect of nitrogen on microstructural evolution and Charpy impact energy of CoCrFeMnNi high-entropy alloy (HEA) was investigated, and the corresponding fracture mechanism was revealed. Nitrogen atoms fully dissolved into the matrix and markedly increased the Charpy impact energy of 0.52N alloy. The fracture morphologies of the 0N...

Phase transformation is rare in pure body-centered cubic (BCC) metals due to the associated high energy barrier. Here, omega (ω) phase transformation in single-crystal niobium (Nb) under compression at 77 K was studied by atomistic characterization and density functional theory (DFT) calculation. The ω phases were found to nucleate preferentially a...

Tensile mechanical properties of fully recrystallized TWIP steel specimens having various grain sizes ( d ) ranging from 0.79 μm to 85.6 μm were investigated. It was confirmed that the UFG specimens having the mean grain sizes of 1.5 μm or smaller abnormally showed discontinuous yielding characterized by a clear yield-drop while the specimens havin...

In order to efficiently explore the nearly infinite composition space in multicomponent solid solution alloys for reaching higher mechanical performance, it is important to establish predictive design strategies using computation-aided methods. Here, using ab initio calculations we systematically study the effects of magnetism and chemical composit...

The effect of nitrogen on microstructural evolution and tensile properties of transformation-induced plasticity (TRIP) Fe50Mn30Co10Cr10 HEAs was investigated. Nitrogen was fully introduced in solid solution by pressure-induced melting technique. Nitrogen addition turned the TRIP alloy to a twinning-induced plasticity (TWIP) alloy, and simultaneousl...

In this study, the evolution of statistically stored dislocation (SSD) and geometrically necessary dislocation (GND) during tensile tests was investigated in CoCrFeMnNi high-entropy alloys (HEAs) with 0 and 0.52 at. % nitrogen. The microstructure characterization indicated that the plastic deformation of the alloys was dominated by dislocation slip...

The Cantor high-entropy alloy (HEA) of CrMnFeCoNi is a solid solution with a face-centered cubic structure. While plastic deformation in this alloy is usually dominated by dislocation slip and deformation twinning, our in situ straining transmission electron microscopy (TEM) experiments reveal a crystalline-to-amorphous phase transformation in an u...

Nanostructured Cu-/Al-laminated composites were processed by accumulative roll-bonding (ARB) technique for four cycles. Microstructural evolutions inside the Cu and Al layers and the interfacial reactions were revealed after annealing at different temperatures. Recovery and recrystallization occurred in the Cu and Al layers at low annealing tempera...

The yield strength of face-centered cubic (FCC) alloy is always insufficient for applications. In this work, different prestrain histories were imposed to improve the yield strength and strain-hardening capability of an ultrafine-grained (UFG) CoCrFeMnNi high-entropy alloy (HEA). In contrast to the specimens prestrained at 293 K, the specimens pres...

Fe–20Mn–0.7C twinning-induced plasticity (TWIP) steel with the grain sizes in the range 1.7–10.2 μm was produced by cold rolling and annealing. The effects of grain sizes on the mechanical properties of the TWIP steel were studied by tensile test at room temperature (RT) and –180°C. The yield strength increased with decreasing grain size at RT and...

Effects of electropulsing treatment (EPT) on the microstructural evolution and mechanical properties of a cold-rolled 316L austenitic stainless steel with nano-lamellar structure were investigated. The EPT experiments were carried out with the electric current direction along the rolling direction (RD) and the transverse direction (TD) of the sampl...

The so-called bimodal microstructure of Ti-6Al-4V alloy, composed of primary α grains (α p) and transformed β areas (β trans), can be regarded as a "dual-phase" structure to some extent, the mechanical 15 properties of which are closely related to the sizes, volume fractions, distributions as well as nano-hardness of the two constituents. In this s...

Mechanical properties of Cu-5at.%Al alloy with different recrystallization fractions ranging from 0% to 100% are studied by tensile tests at 77 K and 293 K, respectively. The relationship between uniform elongation and recrystallization fraction had been unveiled. The uniform elongation and recrystallization fraction have a transition from single-s...

We reported a nitrogen-containing CoCrFeMnNi high-entropy alloy (HEA) with ultrafine-grained structure. Nitrogen addition significantly enhanced the yield strength and retained high ductility, due to the increase of lattice frictional forces and the maintaining planar slip and twinning, providing an accessible way to ameliorate mechanical propertie...

Dislocation-solute interaction plays fundamental roles in mechanical properties of alloys. Here, we disclose the essential features of dislocation-carbon interaction in austenitic Fe at the atomistic scale. We show that passage of a Shockley partial dislocation in face-centered cubic iron is able to move carbon atoms on the slip plane forward by on...

A composite high manganese structure comprising recovered and recrystallized structures was prepared using a single-phase austenitic Fe-30Mn-0.14C-7Cr-0.26Ni steel by cold rolling and annealing. The yield strength and elongation of the composite increased simultaneously, when the tensile temperature decreased from room temperature (RT) to low tempe...

In order to efficiently explore the nearly infinite composition space in multicomponent solid solution alloys, it is important to establish predictive design strategies and use computation-aided methods. In the present work, we demonstrated the density functional theory calculations informed design routes for realizing transformation-induced plasti...

Dislocation-solute interaction plays fundamental roles in mechanical properties of alloys. Here, we disclose the essential features of dislocation-carbon interaction in austenitic Fe at the atomistic scale. We show that passage of a Shockley partial dislocation in face-centered cubic iron is able to move carbon atoms on the slip plane forward by on...

Severe plastic deformation (SPD) have had a revolutionary impact in fabricating ultrafine grained (UFG) or nanostructured metallic materials with bulky dimensions. It is, however, difficult to understand from a viewpoint of conventional metallurgy why UFG microstructures form in the as-deformed (as-SPD-processed) state without annealing process. Th...

Single-phase equiatomic CoCrFeMnNi high-entropy alloy (HEA) specimens with three different grain sizes (0.65 μm, 2.1 μm and 105 μm) were processed by cold rolling and annealing treatment. Tensile properties were investigated over a broad temperature range from 77 K to 873 K. Superior strength-ductility balance can be achieved by refining grain size...

The fatigue crack propagation behavior is a key issue for the service of engineering materials. The effect of electropulsing treatment (EPT) on the growth of fatigue crack in a high‐strength steel (AISI 4340 steel) is investigated. It is shown that the crack propagation rate could be significantly declined via high‐density EPT. The crack features o...

CoCrFeMnNi high-entropy alloy (HEA) exhibits excellent combination of strength and ductility, but low yield strength. In order to ameliorate the mechanical properties, prestrain was applied in this work. The HEA prestrained at 77 K possesses higher yield strength and uniform elongation than the HEA prestrained at 293 K, indicating that the trade-of...

Bulk ultrafine-grained (UFG) CoCrFeMnNi high-entropy alloy (HEA) with fully recrystallized microstructure was processed by cold rolling and annealing treatment. The high-cycle fatigue behaviors of the UFG HEA and a coarse-grained (CG) counterpart were investigated under fully reversed cyclic deformation. The fatigue strength of the UFG HEA can be s...

A remarkable Lüders-type localized deformation having a huge Lüders strain of 0.4 was observed in tensile deformation of an ultra-fine grained austenitic stainless steel fabricated by two-step cold rolling and annealing processes. It was clarified that the Lüders-type deformation in the material was essentially the same as necking caused by plastic...

CoCrFeMnNi high-entropy alloys (HEAs) with partially recrystallized (PR) structure were fabricated by cold rolling and annealing. The microstructures were characterized and the tensile properties were tested at 77 K and 293 K, respectively. In contrast to the early necking at 293 K, an ultrahigh yield strength of 1692 MPa and a considerable uniform...

Tensile properties and microstructural evolutions of Fe–22Mn–1.0C (wt%) twinning‐induced plasticity steel are investigated in the temperature range from 293 to 443 K. An unexpected enhancement of strength and ductility is observed at the elevated temperature of 443 K (≈400 MPa ultimate tensile strength and ≈10% true strain improvements). The twinni...

Similar to the conventional alloys, attaining excellent combination of high strength and ductility is still challenging in the high-entropy alloys (HEAs). In this work, a fully recrystallized ultrafine-grained (UFG) microstructure was introduced into the single-phase CoCrFeMnNi HEA via cold rolling and annealing process. The UFG HEA displays ultrah...

We report a novel method, named as stepping refining (STR) processing, to prepare three-dimensional nanograined bulk of high-Mn twinning-induced plasticity (TWIP) steel for the first time. After STR processing, the average grain size reduces to 20 nm—which is smaller than any reported grain size of TWIP steel—and the hardness reaches to 5.8 GPa, ap...

The mechanical properties of cold‐rolled (CR) and partially recrystallized (PRX) Cu–Al alloy are investigated by tensile tests at 77 and 293 K. While the uniform elongation is limited for the CR specimens at both temperatures, uniform elongation is enhanced unprecedentedly from 2.4% at 293 K to 16.5% at 77 K for the PRX specimens. In contrast to th...

The fatigue of metallic materials can be divided into high-cycle fatigue (HCF) and lowcycle fatigue (LCF); the damage of these two types of fatigue is commonly evaluated through stress amplitude and strain amplitude of cyclic loading, respectively. The mismatch of the evaluation standards between HCF and LCF leads to difficulties in the design and...

Comparison on the kinetics of two different phase transformations, including phase transformation after deformation and phase transformation during deformation (i.e. dynamic transformation, DT), reveals a new discovery that the transformation kinetics can be significantly enhanced in DT even under low driving forces. DT enables continuous generatio...

In this paper, a laser metal deposition (LMD) process has been applied to the fabrications of CrMnFeCoNi high entropy alloys. The microstructures and mechanical properties of the CrMnFeCoNi alloys prepared using casting technique and LMD technique have been investigated. It has been found that the CrMnFeCoNi samples prepared using casting show a co...

A CuAg7Zr0.05 alloy was processed by high-pressure torsion (HPT) for 10 revolutions, and subsequent annealing resulted in a fully recrystallized ultrafine-grained (UFG) microstructure. A minimum mean grain size of 117 nm was successfully achieved, which is quite uncommon via conventional deformation and annealing process. Tensile tests indicate tha...

Three kinds of Fe–22Mn–0.6C–(x)Al (wt%) Twinning-Induced Plasticity (TWIP) steels were designed by changing the Al content. Uniaxial, unloading-reloading and stress-relaxation tensile tests were carried out to evaluate the mechanical properties. Meanwhile, electron channeling contrast imaging (ECCI), transmission electron microscopy (TEM) and X-ray...

Tensile tests and microstructure observations were conducted for two types of twinning-induced plasticity steels, Fe-22Mn-0.6C and Fe-30Mn-3Si-3Al (wt pct), from 293 K to 443 K. With increasing temperature, Fe-22Mn-0.6C steel exhibited enhanced mechanical properties and stable twinning capability, but Fe-30Mn-3Si-3Al steel displayed a decline on it...

Ultrafine grained (UFG) steels with grain sizes around 1 micron exhibit an excellent strength-ductility combination and have been extensively studied worldwide. Among the different grain refinement strategies, thermomechanical controlled processing (TMCP) employing dynamic transformation (DT), that is, ferrite transformation during deformation of a...

Enhancing strength-ductility synergy of materials has always been a hot but difficult topic in material science, for most structural materials, steels in particular, it is inevitable to sacrifice ductility when increasing strength, and vice versa. In this study, by introducing a linear gradient in grain size into Fe-Mn-C twinning-induced plasticity...

The effect of nitrogen addition on the mechanical properties of Fe–22Mn–0.6C (wt%) twinning-induced plasticity steel was studied. It was found that the stacking fault energies of the two steels were comparable, and the twinned grain fractions of FeMnC and FeMnC-N steels were similar before the true strain of 0.5. With increasing the strain to 0.7,...

As a significant scientific problem directly impacting on the long-term safety of engineering materials and facilities, the improvement of fatigue strength under fully-reversed cycling was comprehensively explored in this study. Advantageous material characteristics for the improvement of fatigue strength were summarized from the achievements of th...

Fully recrystallized CoCrFeMnNi high entropy alloys (HEAs) with different grain sizes ranging from 503 nm to 88.9 μm were fabricated by cold rolling and controlled annealing. Tensile tests were conducted at ambient temperature, and deformation microstructures were investigated using electron channeling contrast imaging (ECCI) and transmission elect...

The tensile, high-cycle fatigue (HCF) and fatigue crack growth (FCG) rate tests of Fe-30Mn-0.9C and Fe-30Mn-0.3C twinning-induced plasticity (TWIP) steels were performed. Meanwhile, the corresponding surface damages, fatigue fracture morphologies and microstructure evolutions were also investigated. It is detected that both the fatigue strength and...

The effects of electropulsing treatment (EPT) on the microstructure and corresponding mechanical properties of a nano-lamellar 316L austenitic stainless steel were investigated. The original 316L stainless steel features a nano-lamellar framework with high density of dislocations via cold rolling. The nanostructured stainless steel was hardened and...

A high efficient magnetic levitation melting technique was reported for fabricating bulk equiatomic CoCrFeMnNi high-entropy alloy (HEA) ingot with a diameter of 110 mm. The bulk ingot can be either forged or rolled. In particular, fully recrystallized ultrafine-grained (UFG) HEA with a minimum grain size of 503 ± 181 nm was successfully obtained th...