Ti Microalloyed Research Articles

Investigating the Role of TiC Precipitation in Dynamic Recrystallization Behavior of a Novel Ship Steel

This study examines the single‐pass thermal compression behavior of Ti‐bearing ship plate steel across a temperature range of 850–1150 °C and strain rates from 0.01 to 7 s−1, employing the Gleeble‐2000D thermomechanical simulator. It delves into the evolution of TiC precipitation and dynamic recrystallization (DRX), along with the austenite decomposition transformation during hot compression and subsequent cooling. Active dynamic recrystallization commences at deformation temperatures above 1050 °C, facilitated by the diminished pinning pressure of TiC carbides. This leads to the development of fine DRX austenite grains, influenced by an increase in strain rates and a decrease in temperature. Simultaneously, the fraction of TiC dispersions decreases as the deformation temperature increases, yet they maintain a consistent size of 5–10 nm. The refined particle size is attributed to their low interfacial energy with the austenite matrix, determined by the first principle to be 0.21 J m−2. Due to the severe deformation and numerous dispersions, specimens subjected to a thermal deformation regime at 850 °C and a strain rate of 7 s−1 present a peak in hardness, reaching a maximum of 324 HV. The Ti microalloying approach offers pivotal insights into improving the rollability and mechanical characteristics of ship plate steel.

Austenite Growth Behavior and Prediction Modeling of Ti Microalloyed Steel.

Previous studies on the austenite grain growth were mostly based on a fixed temperature, and the relationship between the austenite grain and austenitizing parameters was fitted according to the results. However, there is a lack of quantitative research on the austenite grain growth during the heating process. In the present work, based on the diffusion principle of the controlled Ti microalloying element, the diffusion process of carbonitrides containing Ti during the heating process was analyzed. Combined with the precipitation model and the austenite growth model, the prediction model of austenite grain growth of Ti microalloyed steel during different heat treatment processes was established. The austenite grain size versus the temperature at four different heating rates of 0.5, 1, 10, 100 °C/s was calculated. The grain growth behavior of austenite during the heating process of Ti microalloyed steel was studied by optical microscope, scanning electron microscope and transmission electron microscope. The experimental data of the austenite grain size was in good agreement with the calculation by the proposed model, which provides a new idea for the prediction of austenite grain size in non-equilibrium state during the heating process. In addition, for Ti-containing microalloyed steels, the austenite grain size increased with the increasing heating temperature, while it changed little by further prolonging isothermal time after certain heating time, which was related to the equilibrium degree of the precipitation and the dissolution of Ti element. The austenite grain coarsening temperature of the tested Ti microalloyed steel was estimated within 1100~1200 °C.

Carbonitride Precipitation Kinetics Model During Continuous Casting of Ti Microalloyed Steel

Carbonitride Precipitation Kinetics Model During Continuous Casting of Ti Microalloyed Steel

Effect of Ti microalloying and laser remelting on the microstructure and mechanical properties of laser powder bed fusion Al–12Si alloy

This study explores the impact of micron-Ti microalloying and laser remelting on the microstructure and mechanical properties of laser powder bed fusion (LPBF) Al–12Si alloy, analyzing the underlying reasons. The findings show that the tensile strength and elongation at 300 °C (184 ± 13 MPa and 7.4 ± 1.4 %) are on par with other LPBF heat-resistant Al alloys, such as near-eutectic Al–Ce and Al–Ni. Introducing micron Ti (1 wt%) to AlSi12 effectively eliminates the α-Al <100> texture and refines the grain structure, thanks to the strong nucleation effect from the formed D022-(Al, Si)3Ti, leading to enhanced tensile strength in both as-built and heat-treated (300 °C for 2 h) samples, while maintaining ductility within the typical range for LPBF near-eutectic Al–Si alloys. Laser remelting further decreases the presence of unmelted Ti powder in AlSi12Ti and encourages the formation of D022-(Al, Si)3Ti, offering insights into LPBF Al alloy composition design through promoting the melt of the modified powder and improving material homogeneity, especially for incorporating micron powders with high melting points. Additionally, the superior mid-high temperature properties (300 °C) of AlSi12+1 wt% micron-Ti contribute to expanding the database of LPBF Al alloys.

High strength and excellent softening resistance Cu–15Ni–8Sn alloy by Ti addition

Cu–15Ni–8Sn alloy is commonly utilized in various applications because of its exceptional strength, elasticity, and softening resistance. Ti microalloying has been employed to enhance the mechanical properties of Cu–15Ni–8Sn alloy. By adding 0.5 wt% Ti, the peak-ageing tensile strength, microhardness, and elastic modulus of the Cu–15Ni–8Sn alloys reach 1401.3 MPa, 479.3 Hv, and 154.7 GPa, respectively, representing the greatest comprehensive performance reported in previous literature. Additionally, the Ti microalloying significantly enhances the softening resistance of Cu–15Ni–8Sn alloys. After ageing at 400 °C for 10 h, the tensile strength of the Cu–15Ni–8Sn-0.5Ti alloy decreases by only around 150 MPa, whereas the alloy without Ti addition experiences a decrease close to 350 MPa. Quantitative analysis reveals that the observed improvements can be attributed to the Ti microalloying inhibiting the dislocation annihilation and the formation of discontinuous precipitation during the ageing process, while simultaneously promoting the precipitation of Ni3Ti. This study provides a theoretical basis for preparing a high-performance Cu–15Ni–8Sn alloy by microalloying.

Numerical Simulation and Experimental Verification of the Quenching Process for Ti Microalloying H13 Steel Used to Shield Machine Cutter Rings

Owing to the non-uniform distribution of chemical composition and temperature during the heat treatment process, the residual stress and deformation of the workpiece emerge as crucial factors requiring consideration in managing the service performance and lifespan of shield machine cutter rings crafted from H13 steel. Considering H13 steel with titanium microalloying as the research object for the shield machine cutter ring, we simulate the quenching process using Deform-3D. The temperature field, phase transformation, stress evolution, and deformation amount after quenching are analyzed. The results demonstrate a strong agreement between the simulation and experimental results, offering valuable insights for optimizing the heat treatment process and enhancing the overall performance of shield machine cutter rings.

Effect of cooling temperature on microstructure and mechanical properties of Ti microalloyed steel

Ti is a relatively inexpensive alloying element. Ti micro-alloying enables steel to have higher strength, which has already been applied to steel products in many domains, including engineering machinery. In this work, the effects of cooling temperature upon the mechanical properties and microstructure of Ti microalloyed steel were researched by OM, TEM, tensile and impact tests. The consequences show that as the final cooling temperature (FCT) decreased, the steel plate microstructure changed from PF + P + B (less) to GB + PF (less)+ P (less), and the grain size decreased obviously. As the temperature further decreased to 607°C, the intragranular dislocation tangles and subgrains increased significantly. The size and number of large TiC precipitates in the steel plate decreased with the decrease of the final cooling temperature. Additionally, the mean size of precipitates decreases gradually. As the FCT varied between 672°C and 645°C, the steel plate strength and low temperature toughness were significantly improved. As the temperature is further reduced to 607°C, the strength increase was reduced. Due to the improvement of grain uniformity, the low temperature toughness was further enhanced to 156 J.

Synergistic effect of Al and Ti micro-alloying in CoCrNi-based medium entropy alloy

Recently, medium and high-entropy alloys with heterogeneous features have exhibited excellent synergistic effects of strength and toughness. In this work, we have produced a series of cast CrCoNi medium entropy alloys with various heterogeneous microstructures through Al and Ti elements micro-alloying. The heterogeneous microstructure and deformation mechanism are systematically analyzed. The result showed that Al/Ti ratio ranging from 0.5 to 2 has a significant influence on the microstructure and mechanical properties of the CrCoNi-based alloy. The present findings provided efficient guidance for developing of microstructure tailoring method in high and medium-entropy alloys.

Unveiling the effects of Ti microalloying and thermomechanical processing on recrystallization behavior and mechanical properties of type 316 stainless steel

For the titanium-stabilized austenitic stainless steels, the interaction of precipitation due to the addition of Ti and the recrystallization process is an important aspect of grain refinement, which needs more systematic investigations. Accordingly, in the present work, the effects of Ti microalloying and thermomechanical processing on the recrystallization behavior and mechanical properties of type 316 stainless steel were investigated. It was revealed that the strain-induced α′-martensitic transformation in these metastable alloys is sensitive to the presence of Ti and C in solid solution or their presence as TiC carbides in the aged condition, as well as the temperature of rolling and reduction in thickness. During annealing, the reversion of deformation-induced α′-martensite to austenite and primary recrystallization resulted in the formation of fine-grained equiaxed microstructures, where the precipitation of TiC and sigma-phase was found to be important in the retardation of recrystallization and grain growth (by Zener pinning mechanism) as well as refining the grain size. Annealing the cold rolled 316Ti stainless steel at 800 °C led to a fine grain size of ∼2.5 μm with the precipitation of sigma-phase; while annealing at 900 °C resulted in a coarser grain size of 4 μm but without the presence of the unfavorable sigma-phase. The yield stress of 476 MPa, ultimate tensile strength of 805 MPa, and total elongation of 68 % were obtained for the latter, revealing the merits of Ti addition and thermomechanical processing for the improvement of mechanical properties.

Effect of Nb, Ti microalloying on hot deformation behavior of high strength steel

The deformation resistance would be increased with the addition of Nb and Ti, which makes it difficult to accurately control the rolling process, resulting in mixed grains and cracks. The hot deformation behavior of Nb–Ti microalloyed high strength steel was investigated in the temperature range of 900–1100 °C with the strain rate between 0.1 and 5 s−1. The recrystallization active energy was obtained by regression calculation, and the thermal deformation equation was established. The dynamic recrystallization critical strain model was established by changing the work hardening rate. The results show that a higher deformation temperature and lower strain rate are conducive to dynamic recrystallization. The active energy of dynamic recrystallization is 386.30 kJ mol−1, εp = 1.23 × 10−2Z0.087, and εc = 1.95 × 10−3Z0.111. The high strength steel is strengthened by the strengthening of grain refining and precipitation of Nb–Ti microalloys. The second phase particles are TiN with a size of about 100 nm, (Nb, Ti)C with the size between 50 and 80 nm, and NbC with the size between 10 and 20 nm.

Study on Hot Flow Behaviors and Deformation/Diffusion Mechanisms of V and V–Ti Microalloyed Steels by Physical Constitutive Modeling

The hot compression tests of medium carbon V and V–Ti microalloyed steels are carried out at the temperature of 900–1100 °C and strain rate of 0.01–10 s−1. Three physical constitutive models based on creep theory are studied, the prediction accuracy is compared and analyzed by employing the correlation coefficient (R) and average absolute relative error (AARE), and the deformation/diffusion mechanisms are discussed. The results show that Ti has obvious hardening effect in V microalloyed steel and retards the onset of dynamic recrystallization. The physical constitutive model containing the theoretical value of creep exponent 5 can accurately describe the hot flow behavior of both steels, the prediction accuracy of which is comparable to that of the model containing exponent n, reflecting that the dominant deformation mechanism of both steels is dislocation climbing. Furthermore, a modified physical constitutive model combining diffusion mechanisms of lattice diffusion and grain boundary diffusion shows higher accuracy (R = 0.996, AARE = 3.81% of V steel and R = 0.994, AARE = 4.52% of V–Ti steel), indicating that the diffusion mechanism is controlled not only by lattice diffusion but also by grain boundary diffusion.

Regulation of performance of laser-welded socket joint of Mo–14Re ultra-high-temperature heat pipe by introducing Ti into both weld and heat affected zone

Fusion welding of molybdenum (Mo) alloys faces problems including grain coarsening and embrittlement, so that the obtained joints have poor mechanical performance. The research took the socket joints of a novel Mo–14Re ultra-high-temperature (UHT) heat pipe as research objects. Pre-heating, titanium (Ti) microalloying and brazing were adopted for coordinated regulation of defects, microstructures, and mechanical performance of joints. Results show that Ti added can be uniformly mixed with metals in the molten pool and solidly dissolved in the matrix to achieve solid-solution strengthening. Ti entering the weld zone distributes on grain boundaries and in grains, thus decreasing the relative content of Mo oxides on the surface of grain boundaries in the meanwhile of grain refinement, playing a role in purifying grain boundaries. Ti alloying in the weld zone to some extent can inhibit occurrence of pore defects and improve the bearing capacity of joints. Moreover, the brazing layer formed in the heat affected zone (HAZ) not only enlarges the bonding and bearing area of joints, but also shifts the position of the stress concentration point of joints from the near weld zone with poor performance to the area with favorable performance much farther from the weld. Under the joint action of Ti microalloying and brazing, the tensile strength of joints is improved from 140.8 to 399.8 MPa. The fracture mode changes from intergranular fracture to transgranular cleavage-like fracture. The research results can promote the development of technologies for manufacturing novel UHT heat pipes and welding Mo–Re alloys.

Characterization and Control of Secondary Phase Precipitation of Nb–V–Ti Microalloyed Steel during Continuous Casting Process

Characterization and Control of Secondary Phase Precipitation of Nb–V–Ti Microalloyed Steel during Continuous Casting Process

Synergistic effects of microalloying and pre-straining on enhanced nanoprecipitation and creep property of alumina-forming austenitic stainless steels

Non-shearable metal carbide (MC) nanoparticles are one of the most effective strengthening media for improving creep resistance of alloys at elevated temperatures. However, it is difficult to achieve sufficient homogeneous dispersion due to their large crystallographic difference with the matrix. Herein, we report a feasible method to form massive NbC nanoprecipitation in an aluminum-forming stainless steel via the combination of microalloying and pre-straining. The employment of pre-straining generated dislocations uniformly distributed inside the alloy matrix, which provides high-density heterogeneous nucleation sites and enables fast pipe diffusion channels for involved solutes, thus substantially enhancing the nucleation rate of the secondary NbC. Moreover, due to its stronger affinity with C and larger diffusivity as compared with Nb, Ti atoms were found to occupy the Nb sublattice of the NbC at the onset of precipitation. The formation of (Ti,Nb)C nuclei with decreased lattice misfit (from 20.8% to 19.1%) effectively reduced the critical nucleation energy barrier and thus enhanced the nucleation rate accordingly. With the synergistic effect of 0.1 wt% Ti microalloying and 10% pre-straining, massive precipitation of refined secondary (Ti,Nb)C nanosized particles (4.4 ± 0.7 nm) with a much increased volume fraction (almost 6.8%) was practically realized, remarkably reducing the steady-state creep rate and prolonging the creep-to-rupture lifetime to 2044 h at 1023 K and 120 MPa. The current findings provide a feasible strategy to disperse strong yet massive nanoparticles within metallic metrics, which may shed new insights into the development of advanced high-temperature alloys with much enhanced creep properties at no expense of oxidation resistance.

Effect of Cooling Rate on Phase Transformation Kinetics and Microstructure of Nb–Ti Microalloyed Low Carbon HSLA Steel

Nb–Ti microalloyed low carbon high strength low alloy (HSLA) steels are used to fabricate components, particularly for the automobile and piping applications requiring optimum combination of mechanical properties along with good weldability. These properties depend on the transformed ferrite microstructure and grain size obtained after cooling from hot rolling temperatures which are always well above the austenitizing temperature. Hence, an attempt was made to study the austenite decomposition (phase transformation) kinetics and the accompanying microstructural evolution in Nb–Ti microalloyed steel by subjecting it to austenitization at 1100 °C for 3 min followed by cooling at different rates ranging from 1 to 100 °C/sec in a B\(\ddot{a}\)hr DIL 805 A/D dilatometer. The first derivative method was employed to identify critical transformation temperatures from the dilation curves. A modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis (used for non-isothermal conditions) was carried out to find the time exponent (n’) values controlling the rate of transformation at different cooling rates. The nature of transformed ferrite was observed to change from polygonal to acicular type, and its grain size was found to decrease with an increase in cooling rate. EBSD analysis also revealed the cooling rate to have a profound effect on the microtexture evolution of the concerned alloy. The “\(\gamma\)” fibre and rotated cube components are replaced by the transformed copper (“\(\alpha\)” fibre) components owing to faster transformation and lack of recrystallization of transformed \(\alpha \) with increase in cooling rate. Finally, a power law and logarithmic relationship of grain size and microhardness with the applied cooling rate were established.

Improvement of Cu-rich precipitation strengthening for high-strength low carbon steel strengthened via Ti-microalloying

This present work aims to improve the precipitation strengthening of nanoscale Cu-rich particles in high-strength low carbon steel by Ti microalloying. Ti microalloying increased the density of small-angle boundaries and dislocations, which increased the nucleation sites and refined the dimension of Cu-rich particles. By adding 0.05 wt% Ti, the size of Cu-rich particles were refined from 22 nm to 7 nm. The structure of Cu-rich particles in Ti-free steel was incoherent FCC-Cu, whose mismatch degree with α-Fe matrix was 0.28. By adding 0.02 wt% and 0.05 wt% Ti, the structure of Cu-rich particles transformed into semi-coherent 3R-Cu and 9R-Cu, respectively. Meanwhile, the mismatch degrees between Cu-rich particle and α-Fe matrix decreased to 0.24 and 0.21, respectively. The refinement of Cu-rich particles increased the precipitation strengthening from 46 MPa to 248 MPa.

Effect of Annealing Process on Microstructure and Electrical Conductivity of Cold-Rolled Ti Microalloyed Conductive Steel

Effect of Annealing Process on Microstructure and Electrical Conductivity of Cold-Rolled Ti Microalloyed Conductive Steel

Modeling of the Dynamic Recrystallization of Ti Microalloyed High‐Strength Steel

The dynamic recrystallization (DRX) and austenite microstructure evolution of Ti microalloyed high‐strength steel are investigated and modeled by thermal simulation experiments. The corresponding mathematical models are established based on DRX‐type flow stress curves and the austenite microstructure. A highly accurate austenite grain growth model under different heating conditions is established, which can predict the initial austenite grain sizes before deformation. Considering the effect of initial austenite grain sizes and deformation conditions, the key parameters (peak stress, steady stress, peak strain, and constants C and C1) of the DRX‐type flow stress model are determined, and the predicted DRX‐type flow stresses are in good agreement with the experimental values. The relationships between critical strain and peak strain(εc = 0.77εp), critical stress, and peak stress(σc = 0.82σp) are determined for experimental steel. The relationships between the initial austenite grain size and the key parameters (k, M, a, h) in the DRX kinetic model and the DRX grain size model are determined. The calculated and experimental DRX volume fractions and grain sizes are in good agreement. The results show that these mathematical models can accurately describe the DRX behavior of experimental steel.

Physical and Apparent Arrhenius Constitutive models of a Nb–Ti Microalloyed C–Mn–Al High Strength Steel: A Comparative Study

Physical and Apparent Arrhenius Constitutive models of a Nb–Ti Microalloyed C–Mn–Al High Strength Steel: A Comparative Study

Application of Ti Microalloying in a Thin-Slab-Cast Medium-Carbon Steel

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