In the high-temperature service environment of 350-500 degrees C for low-pressure steam turbine rotors, 30Cr2Ni4MoV rotor steel usually exhibits serious aging embrittlement after long-term aging, which can induce intergranular fracture (IGF). Mn partitioning at grain boundaries (GBs) and its effect on aging embrittlement of 30Cr2Ni4MoV rotor steel during aging at 500 degrees C for 0-10,0 0 0 h were investigated mainly by electron backscattering diffraction (EBSD), transmission Kikuchi diffraction (TKD) and atom probe tomography (APT). Aging at 500 degrees C, there is limited Mn partitioning between M23C6 and matrix. And before aging, Mn is uniformly distributed at GBs. But after aging, Mn enrichment level at GBs increases, and H-GBs with larger misorientations contain higher Mn enrichment. The tensile and impact testing results reveal that Mn partitioning at H-GBs and L-GBs during aging has a relatively small effect on the tensile properties, but reduces impact toughness. During impact process, crack initiation energy remains stable due to small variation of M23C6 size. Interestingly, crack propagation energy drops obviously after Mn partitioning at H-GBs. The reason is that Mn partitioning at H-GBs decreases GB cohesion and promotes crack propagation along GBs with mainly H-GBs, leading to IGF formation. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

High-manganese (Mn) steel with an appropriate Mn content exhibits an exceptional damping capacity, which makes it an important and promising structurally and functionally integrated material. In fact, the interstitial carbon atoms in high-Mn damping steel not only inhibit epsilon-martensitic transformation and formation of stacking faults, which can affect the mechanical properties, but also impede the movement of partial dislocations, thereby deteriorating the damping capacity. In this study, we propose the strategy of using vanadium (V)-microalloying to deplete carbon atoms, attempting to reduce the adverse effects of carbon atoms. The results show that after Vmicroalloying in Fe-17Mn-V steel, both the mechanical properties and damping capacity have been improved. The strength increase primarily comes from coordinate grain refinement, carbide precipitation, and controlled martensitic transformations; in addition, the enhancement of damping capacity is closely related to the precipitation of V-rich carbides. The V-rich carbides reduce the weak pinning points (C and Cr atoms), thereby lowering the resistance of partial dislocations during the bowing out and breakaway movements. At high strain amplitude, the planar slips of partial and full dislocations are the primary damping mechanisms, and the damping capacity increases rapidly. Moreover, the planar slips of partial and full dislocations can bypass the Vrich carbides, dissipating more energy and further improving the damping capacity. The V-microalloying highMn damping steels exhibit an outstanding combination of mechanical properties (tensile strength >950 MPa, elongation >43.0%) and damping capacity (0.041, strain amplitude of 0.1%, frequency of 1 Hz).

20Cr1Mo1VTiB bolt steel is widely used as a high-temperature fastener in thermal power plants, where it operates under complex stress conditions. However, this steel undergoes significant strength-toughness degradation after prolonged high-temperature service, and the microstructural mechanisms responsible for this degradation under real service conditions remain unclear. In this work, the microstructure evolution of this steel served after 1.30 x 105 h was systematically analyzed. We found that long-term exposure promoted the continuous precipitation of M6C carbides along grain boundaries, and facilitated the co-precipitation of Laves phases, accompanied by Ostwald ripening-induced coarsening of VC carbides, grain coarsening, and a reduction in dislocation density. Correspondingly, the yield and tensile strengths decreased from 809 +/- 8 and 890 +/- 6 MPa to 720 +/- 7 and 833 +/- 12 MPa, respectively. Especially, severe impact toughness deterioration was also observed, with absorbed energy sharply dropping from 132 to 34 J and the fracture mode shifting from ductile to brittle. These precipitation clusters lower the critical stress for cracking, concentrate boundary stress, and weaken strain compatibility, promoting crack propagation along prior-austenite grain boundaries. This work provides microstructural evidence and a mechanistic understanding of this steel's degradation under true service conditions, offering guidance for service life assessment and alloy optimization of high-temperature fasteners. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Pre-deformation is a simple and effective method to improve the strength and damping capacity of Fe–Mn damping alloys. Unfortunately, there is still a lack of in-depth understanding of the multiple martensitic transformations and strengthening mechanisms after pre-deformation, especially the exact correspondence between pre-deformation parameters and damping capacity, as well as the damping mechanisms. In this study, Fe−17.2Mn−0.05C−0.45Si−0.36Cr−0.05V alloy after annealing was used as the experimental material. Various microstructural characterization techniques, tensile and damping testing methods were used to reveal the effects of 2 to 8 pct cold rolling pre-deformation on the microstructure, mechanical properties, and damping capacity, attempting to clarify the strengthening and damping mechanisms after cold rolling pre-deformation. The results show that the strength and damping capacity of this alloy are significantly improved after pre-deformation. Dislocation multiplication, deformation-induced stacking faults and γ → ε transformation mainly occur, resulting in the increase of dislocation, stacking faults, and ε-martensite. Additionally, a small amount of α′-martensite is induced due to the ε → α′ transformation. The increment of strength is mainly attributed to dislocation strengthening, grain boundary strengthening, and hardened α′-martensite structure. After appropriate pre-deformation, the multiple martensitic transformations are promoted during tensile deformation, which ensure that the elongation does not significantly decrease. Quantitatively, at cold rolling pre-deformation ratio of 4 pct, this alloy exhibits the best combination of strength and plasticity, with a tensile strength of 1010 ± 8 MPa, a yield strength of 627 ± 9 MPa, and an elongation of 38.8 ± 0.5 pct. The enhanced damping capacity is mainly due to the increase in damping sources, especially the γ/ε and ε/ε interfaces, while it is closely related to the applied strain amplitude and cold rolling pre-deformation ratio. After 2, 4, and 8 pct pre-deformation, the damping capacities at strain amplitudes of 0.01 and 0.08 pct are increased by 7.6, 16.5, 13.2, and 11.8, 18.1, 22.6 pct, respectively.

To achieve isotropic strength in GH3536 foil, this study investigated the influence mechanism of initial recrystallization microstructure and texture characteristics of GH3536 superalloy foil with different cold-rolled reduction rates (referring to the reduction rate in thickness) on annealing recrystallization microstructure, including secondary recrystallization microstructure, and texture. This was studied by controlling the cold-rolled reduction rate and annealing temperature, in conjunction with microstructure and texture analysis. Meanwhile, this study clarified the dependency of strength performance on recrystallization microstructure and texture. The results of this study indicate that the Coincidence Site Lattice (CSL) grain boundaries and High Energy (HE) grain boundaries did not show significant superiorities, and were not the primary reasons for the formation of Brass ({011}<211>) and Goss ({011}<100>) textures, as well as secondary recrystallization. Instead, by controlling the cold-rolled reduction rate, the initial recrystallization stage formed a significant quantity and size superiority of alpha-fiber texture ({110}& Vert;ND) in each grain size range. This led to preferential growth, and even abnormal growth of Brass and Goss grains in subsequent high-temperature annealing processes. The control of the alpha-deformation fiber texture was identified as the driving factor behind the formation of the initial recrystallization texture due to the cold rolling reduction rate. Cold-rolled processes with a deformation amount greater than 40 % yielded a quantity superiority of alpha-fiber texture shear bands and an appropriate stored energy advantage. This facilitated the nucleation and effective growth of more alpha grains, while suppressing the random growth of grains with gamma-fiber texture ({111}& Vert;ND). Ultimately, a quantity and size superiority was achieved in the initial recrystallization stage. The tensile strength of GH3536 foil was controlled by grain size and texture. By controlling the deformation amount to approximately 30 %, GH3536 foil was successfully produced with no pronounced orientation texture and isotropic strength.

用光学显微镜(OM)、扫描电镜(SEM)及X射线衍射分析(XRD)等手段表征不同厚度的冷轧态GH3536微米尺度带箔材退火后的显微组织和结构特征,研究这种材料的再结晶和晶粒长大的规律.结果表明,冷轧变形后的GH3536带箔材的晶粒组织呈线条状,其主相为γ相;建立了厚度为200、100和50 μm的GH3536带箔材在1050～1150℃退火10～60 min的晶粒长大方程,得到晶粒长大的激活能分别为Q200μm=800.34 kJ/mol,Q100μm=609.50 kJ/mol,Q50μm=314.79 kJ/mol.厚度较小的GH3536带箔材其晶粒长大激活能也较小,晶粒更容易长大.影响晶粒长大的因素与变形程度和析出相颗粒有关.

Herein, the residual mechanical behaviors of a 690 MPa grade high‐strength steel after exposure to fire for an extended duration are investigated, and the factors affecting their variation based on the theories of metallurgy are explored. The corresponding tensile properties and microstructure tests are conducted on this steel soaked at 300–900 °C for 3 h and then cooled in air. The results show that there is negligible influence of temperature on residual mechanical properties at 600 °C or lower. It can be considered that the critical fire temperature is 600 °C, beyond which the strength decreases sharply. This can be attributed to the formation of ferrite and grain coarsening. However, at 900 °C, its residual strength can still maintain approximately half of that at room temperature. It is related to the contribution from fine nanoscaled precipitates of 10–40 nm in size. Compared with steels having the same nominal yield strength, the dependence of residual mechanical properties on elevated temperatures for this steel varies due to the difference in microstructure characteristics. New predicted equations are proposed for this novel structural steel to guide on better prediction of residual mechanical properties in steel structure systems.

The grain boundary distribution characteristics and their formation mechanism in GH3536 superalloy strip and foil prepared by multi-pass "cold-rolling and annealing " at different annealing temperatures (including subsolvus and supersolvus temperatures) were studied in this paper. According to the results of this study, the grain size of strip and foil of a thickness of 200 mu m was unevenly distributed along the strip when annealed at 1050 ?. The deformation energy storage of the strip and foil of 200 mu m thickness was low, and its recrystallization temperature was higher than that of strip and foil with a thickness of 100 mu m and 50 mu m. Therefore, the annealing process at 1050 ? was conducive to promoting the interaction and decomposition of coincident site lattice (CSL) grain boundaries through the movement of dislocations in the recovery process, so that CSL grain boundaries formed low-energy grain boundary clusters and interrupted random grain boundaries. In the process of grain growth of GH3536 strip and foil, the "accidental " growth mechanism of sigma 3 annealing twin boundaries was dominant. With the increase in grain size, the proportion of sigma 3 grain boundary increased. The parallel sigma 3 twin boundary formed by this mechanism was not conducive to breaking the random grain boundary. After annealing at a supersolvus temperature of 1200 ?, the grains grew under the action of high thermal activation energy, the proportion of sigma 3 grain boundary decreased, and its reduction was more prominent in strip and foil of 50 mu m thickness with large cumulative deformation. When annealing twice at the selected supersolvus temperature, strain-induced grain boundary migration dominated, which reduced the dislocation density and deformation storage energy of the microstructure and was thereby conducive to the formation of sigma 3 grain boundaries by the "accidental " growth mechanism; furthermore, the proportion of sigma 3 grain boundary increased in the process of grain coarsening.

In this article, thermomechanical controlled processing (TMCP) plus tempering (T) is adopted to acquire a novel 690 MPa‐grade high‐strength low‐carbon bainitic construction structural steel, which has an optimum balance of strength‐ductility and lower yield ratio (YR). The results show that the as‐rolled steel consists of bainitic ferrite, lath‐like bainite, and granular bainite. With an increase in the tempering temperature, a great deal of carbonitrides precipitates and maintains a small nano‐scaled size without coarsening. Their interaction with dislocations induces an increase in strength. When the tempering temperature further increases, some grain boundaries between adjacent bainitic laths gradually blur or even disappear, and the average width of the bainitic laths increases to ≈860 nm. The recovery of bainitic laths is the main reason for the decreased strength. Due to the synergistic effect of the small dot‐shaped martensite/austenite (M/A) constituents and grain boundaries misorientation distribution, maximum impact absorbed energy is achieved after tempered at 500 °C. Furthermore, the lower YR is achieved by appropriate control of strength difference between the soft bainitic ferrite and hard M/A constituents via tempering.

In this article, the rusting evolution of 690 MPa grade multifunctional construction structural steel was investigated under a simulated industrial atmospheric environment. The corrosion product stabilization process was examined using the corrosion mass loss method, electrochemical measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The results indicated that the corrosion kinetics exhibited a two-stage process, including a rapid stage followed by a slow stage. The initial sharp rise in corrosion rate was related to the involvement of reducible corrosion products in the cathode reduction process, which accelerated the dissolution of the anodic steel substrate. The appearance of the inflection point in the corrosion stage was strongly associated with the accumulation of corrosion products. As the corrosion time progressed, the corrosion products changed from porous to compact structures because of the synergistic effects of Cu, Ni, and Cr. This compact, thick, and uniform rust layer was identified to contain aggregates of crystalline γ-FeOOH along with a large number of fully grown flowery-shaped α-FeOOH on its top. Thus, the corrosion resistance increased when the rust layer gradually accumulated, and the diffusion of the corrosive ions was obstructed owing to the inhibited electrochemical corrosion. After a prolonged dry–wet cyclic corrosion, the rust layer led to stress cracking, but its self-repairing ability would make the cracks die.

通过阳极动电位极化测试、电化学阻抗谱(EIS)测试及钝化膜电容测试等电化学腐蚀方法,研究了在不同温度的典型介质(NaCl质量分数为3.5％的溶液)中444铁素体不锈钢的耐点蚀行为及其影响规律.结果表明,随着介质温度的升高,444铁素体不锈钢的自腐蚀电位Ecorr和点蚀电位Ep均呈现降低趋势,而自腐蚀电流密度icorr增大,不锈钢耐蚀性降低.在不同介质温度下,444铁素体不锈钢表面钝化膜的半导体类型未发生改变,但是钝化膜中点缺陷密度随温度的升高而增大.此外,腐蚀形貌观察结果也表明,不锈钢表面蚀孔的数量也随温度的升高而增加.

The present article aims at elucidating the effect of thermo-mechanical controlled processing (TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at −20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.

采用高温高压气相热充氢方法将氢充入SA508-3钢,采用J积分方法比较不同载荷速率下未充氢与充氢钢的断裂韧性,考察氢对SA508-3钢断裂韧性的影响.结果表明,在相同载荷速率下,与未充氢SA508-3钢相比,充氢钢断裂韧性明显降低,充氢断口均为韧性和脆性混合断口形貌.随着载荷速率的降低,断裂韧性损失逐渐增加,准解理所占面积增加,脆性提高.在三向应力的作用下,氢与静水应力的交互作用能大于氢与可动位错的交互作用能,静水应力更易捕获到氢.SA508-3钢断裂韧性测试过程中,在三向应力的诱导下会促进氢富集在裂纹尖端碳化物和基体的界面处,从而降低了碳化物和基体的结合强度,致使阻碍裂纹扩展的能力减弱,因此钢充氢后断裂韧性降低.随着载荷速率的降低,三向应力作用在裂纹尖端的时间增加,氢富集在碳化物和基体界面浓度增加,氢压增强,加速裂纹扩展,钢的脆性提高,断裂韧性损失增加.

Influences of cooling time (welding heat input) on microstructure, impact toughness and the fracture mechanism of the weakest CGHAZ (coarse-grained heat-affected zone) in a novel high-strength low-carbon microalloyed construction steel were studied for the purpose of laying a theoretical foundation for developing welding support technologies. When the cooling time (t(8/5)) was increased, the microstructure changed from dot shape M-A constituents and lath martensite/bainite to slender and blocky M-A constituents and coarse granular bainite. Accordingly, the impact toughness deteriorated. Large blocky M-A constituents seriously reduced the impact absorbed energy during crack initiation. For coarse bainite, the high-misorientation boundary almost disappeared. Therefore, crack initiation energy determines the cleavage fracture micromechanism of high heat input construction steel.

The rapid development of high-rise buildings has increasingly brought requirements for construction steels with high strength and toughness. For high-rise building structural steels with low yield ratio, good weldability and excellent resistance to fire and corrosion are generally required. However, high grade construction steels with comprehensive properties are yet to be developed. In this study, a 690 MPa grade functionally structured fire and corrosion resistant high strength construction steel was designed based on the thermodynamic calculations of the JMatPro software and interactions among chemical elements. The chemical composition (mass fraction, %) of the designed steel was Fe-0.08C-0.3Si-1.1Mn-0.12(Nb + V + Ti)-1.6(Cr + Cu + Ni + Mo)-0.002B-0.004N. After laboratory melting and a thermomechanical controlled process (TMCP), the microstructure features, strengthening and toughening mechanisms, mechanical properties, and fire and corrosion resistances were characterized and analyzed by EPMA, EBSD, and performance testing. Results show that the microstructure of this low-carbon microalloyed steel at its TMCP state is mainly composed of bainite ferrite, granular bainite, and lath-like bainite. The yield strength, tensile strength, total elongation, and yield ratio at room temperature are 700 MPa, 878 MPa, 20%, and 0.80, respectively, and this steel possesses good low-temperature toughness. This low-carbon microalloyed steel meets requirements for fire resistance at elevated temperatures up to 600 degrees C for 3 h. It is disclosed that the granular bainite plays a positive role in improving corrosion resistance under marine environment. A further analysis shows that the tested steel possesses excellent strength and toughness resulting from the cumulative effects of precipitation strengthening, grain refinement strengthening, dislocation strengthening, and solid solution strengthening. Moreover, after observation and analysis of crack initiation and propagation underneath the fractured surface of low-temperature impacted samples, the microvoids prefer to nucleate at high-angle boundaries containing brittle phases and grow in a Z-type to cross lath-like bainite to consume more energy. Multiple crack deflections are beneficial for toughness improvements.

In order to improve mechanical properties of roll cast 8011 aluminum alloy (AA 8011) by grain strengthening, and expand its application field, the effect of different annealing treating processes on mechanical properties and microstructures of cryogenic rolled AA 8011 was investigated. The roll cast AA 8011 was cryogenic rolled for six passes and then annealed. The annealing treatment was adopted at 100–300 °C for 1 h, and then the annealing treatment was adopted at 220 °C for 10–80 min. The microstructures of AA 8011 under roll cast and cryogenic rolled states were studied by using OM. The grain size was calculated by the Image-pro-plus 5.0. The microstructures of AA 8011 under annealing states were observed by using TEM and energy dispersive spectrum analysis. The results show that the second phase Al8Fe2Si appears in the cryogenic rolled AA 8011 after annealing treatment. When the dislocation moves in the grain, the dislocation plays a pinning role, which is conducive to grain refinement. The optical annealing treatment was treated at 220 °C for 40 min with optimal thermal stability. The ideal grain size is 1 μm, hardness is 65 HV, and tensile strength is 202 MPa. It is about 1.5 times of the roll cast AA 8011.

将超纯铁素体不锈钢439板材在不同冷轧变形率下冷轧变形,然后将轧制态冷板在950 ～1050℃下进行退火,研究冷轧变形率对该材料退火组织及性能的影响.结果表明:随着变形率的增加,晶粒尺寸变小;50％变形率条件下冷板最高伸长率为36％,80％变形率条件下最高伸长率可达40％;基于金相试验数据,利用回归分析的方法计算了不同变形率条件下的晶粒长大激活能,得出50％和80％冷轧变形率条件下再结晶晶粒长大激活能分别为60.19 kJ/mol和65.68 kJ/mol;采用晶粒尺寸与晶界迁移激活能间的定量关系来描述晶粒长大过程,最终建立了该合金在试验温度范围内再结晶晶粒长大的动力学模型.

通过细晶强化方式研究了不同退火温度和时间对深冷轧制态1060铝合金显微组织和力学性能的影响.对铸轧态1060铝合金进行六道次深冷轧制,然后对其进行退火处理,退火工艺分别为:在100～300℃ 保温1 h以及在260℃ 保温10～80 min.结果表明,深冷轧制态1060铝合金经退火处理后有第二相Al8 Fe2 Si1出现,在晶粒内部位错发生运动时,对位错起到钉扎作用,有利于晶粒细化.深冷轧制态1060铝合金最佳退火处理工艺为退火温度为260℃,保温50 min,热稳定性能良好,晶粒尺寸理想,晶粒大小约为1.5μm,硬度为45 HV5,抗拉强度为149 MPa,力学性能均为铸轧态的1.5倍以上.

采用高温高压气相热充氢方法将氢充入SA508-III钢,通过比较不同应变速率充氢钢的拉伸变形行为,考察氢对SA508-III钢氢脆敏感性的影响.结果表明,随应变速率降低,钢的屈服强度增加幅度减小,而钢的氢脆敏感性增强.钢的氢脆主要取决于氢与位错的相互作用,当应变速率高于5.21×10-3 s-1时,柯氏氢气团的迁移速率跟不上位错的滑移速率,氢对位错源开动的阻碍作用增强,因而屈服强度增加幅度加大.当应变速率低于5.21×10-3 s-1时,柯氏氢气团随可动位错一同运动,此时氢对位错源开动阻碍作用减弱,因而屈服强度增加幅度减小,但位错可将氢传递到碳化物与基体界面处,造成局部氢浓度升高,形成氢致裂纹,裂纹扩展进入铁素体基体内形成准解理断裂,故SA508-III钢的氢脆敏感性增加.保持SA508-III钢低氢脆敏感性的最大应变速率为5.21×10-3 s-1.

The influence of austempering time and vanadium addition on microstructure and mechanical properties of the alloyed ductile iron has been investigated. The 0.30 wt% V-containing and V-free alloyed ductile irons were firstly austenitized at 850 °C for 1 h and then austempered in a salt bath at 300 °C for 2, 3 and 4 h, respectively. For the 0.3 wt% V-containing alloyed ductile iron, the transformation product (ausferrite) was finer, and a small amount of martensite and a large amount of stable austenite were obtained after austempering for 2 h, while higher hardness and compressive strength of 62.8 HRC and 3000 MPa were achieved. For the V-free alloyed ductile iron, lower hardness and compressive strength were measured to be 56.8 HRC and 2320 MPa. As the austempering time increases, the amount of stable austenite decreases in the V-containing ductile iron, typically for the start of the second stage formation (retained austenite (γr) → α + carbide). Based on this, it is assumed that the optimal processing window (OPW) was narrowed due to the addition of 0.30 wt% V as compared to the V-free ductile iron. When the hardness of 0.30 wt% V-alloyed ductile iron was higher than 59 HRC, the highest wear resistance was obtained. The mechanical cutting plays a dominant role in abrasive wear process.