Metallurgical and Materials Transactions A最新文献

The effect of Ru addition on the martensitic transformation and mechanical properties of Zr₅₀Pd_50−xRu_x SMAs shape memory alloys has been studied. Strain–temperature experiments, differential scanning calorimeter, and scanning electron microscope analyses were performed to validate the theoretical predictions by DFT calculation regarding the influence of the C′ parameter on martensitic stability. Despite the absence of an observed shape memory effect under the tested conditions, the findings suggest that ZrPdRu alloys hold promise for high-temperature applications.

During thermo-mechanical processing, dissolved alloying elements have a huge impact on the microstructure evolution by influencing the overall dislocation storage rate. Especially, for non-heat treatable Al alloys, the effects of strain-hardening and solid solution strengthening are of significant practical interest. In the present work, a detailed study of the room temperature work-hardening behavior of binary Al–Cu, Al–Zn, and Al–Mn alloys with varying solute concentrations is carried out. Stress–strain curves at different strain rates are recorded and computationally analyzed by an advanced 3-Internal-Variables-Model (3IVM) approach for the dislocation density evolution. The initial strengthening rate is examined as a function of the solute concentration.

Refining the grain size of the as-casted hypoeutectic Al–Si alloys is an established technique for improving their mechanical properties. This work is based on the development of a novel La-riched grain refiner, i.e., Al–3Ti–4.35La, which exhibited remarkable efficiency for grain refinement from 1.46 mm into ~ 0.1 mm (with 0.2 wt pct of the refiner), increasing both tensile strength, yield strength, elongation and hardness from 154.3 MPa, 64.5 MP, 5.83 pct, and 54.8 HV to 178.3 MPa (an enhancement of 15.6 pct), 77.5 MPa(an enhancement of 20.2 pct), 12.02 pct (an enhancement of 106.0 pct), and 58.4 HV (an increase of 6.6 pct), respectively. The in situ formation of the Ti₂Al₂₀La phase served as the nucleus for α-Al during solidification. The segregation of trace Si and La atoms at the interface indicates their chemical affinity with a relatively lower energy configuration, which is consistent with the first-principles calculations. The results of this study offer an innovative approach for attaining considerable grain refinement in Al–7Si alloys by constructing rare-earth grain refiners.

Additive friction stir deposition (AFSD) is a solid-state additive manufacturing method that exploits frictional heat generation and severe plastic deformation to achieve metallurgical bonding during layer-by-layer deposition. AFSD can be used for additive manufacturing of bulk components or repair of aluminum alloys as the sub-solidus processing temperatures can be beneficial over fusion-based alternatives. Due to dynamic recrystallization during AFSD processing, significant evolution of the microstructure can occur which can lead to substantial gradients in grain and intermetallic particle size. In this study, we present a history dependent modeling framework to predict the microstructure evolution in the AFSD process through mesh-free numerical simulations. In this work, experimentally quantified relationships between grain and intermetallic particle size as well as temperatures and strain rates were incorporated into a smooth particle hydrodynamic simulation framework to predict the microstructure after AFSD processing. The SPH simulation approach showed reasonable agreement between the model predictions and experimental results of grain and intermetallic particle size distribution after AFSD processing.

A study was conducted to investigate the temperature dependence of thermomechanical coupling in Inconel 718 (IN718). IN718 was selected as a model material due to deformation being predominantly accommodated by planar slip. Split-Hopkinson (or Kolsky) tension bar experiments were conducted at a nominal strain rate of 750 s(^{-1}) at room temperature and (450,^{circ })C, representing homologous temperatures ((T_H = T/T_{melt})) of (T_H=0.2) and (T_H=0.5), respectively. During deformation, specimen gauge sections were imaged with a high-speed infrared camera. Using one-dimensional wave analysis, the transient heat conduction equation, and temperature-dependent specific heat capacity values, the temperature rise as a function of plastic strain was used to calculate plastic work, thermal work, and the plastic work to heat conversion efficiency, commonly known as the Taylor–Quinney coefficient (TQC). As expected, a significant reduction in plastic work was observed during testing at elevated temperatures. The temperature rise due to plastic deformation was observed to be lower at room temperature compared to elevated temperature experiments. It is reported here for the first time that the TQC is a temperature-sensitive quantity. At (T_H=0.5), a nearly complete conversion of plastic work to heat was observed (TQC (approx,1.0)). Under ambient conditions of (T_H = 0.2), a much lower efficiency TQC (approx,0.4) was observed.

The as-prepared and thermally treated Ni–P and Ni–Fe–P alloy powders obtained by chemical reduction were studied regarding the microstructure, as an important factor affecting the functional properties of the materials. Also, the influence of the microstructure and thermally induced transformations of the studied materials on the corrosion behavior in neutral, alkaline, and acidic media is presented. For a detailed study of the mentioned phenomena, different structural and electrochemical techniques were used, including XRD, TEM, DTA, potentiodynamic, and EIS measurements. The composition and microstructure of the studied alloy powders were shown to be dependent on the reactant ratio and thermal history of the material. Small amounts of crystalline phases present in the as-prepared powders, as well as crystalline phases formed during crystallization, included some or all of the following phases: Ni, Ni₃P, and Ni₁₂P₅. It was shown that the addition of small amount of Fe into the Ni–P powder alloy considerably affects the microstructure and thermal stability of the material, having beneficial effect on the formation of protective oxide layers and thus on the corrosion resistance in chloride environments.

The evolution of the microstructure and mechanical properties of Al–5.76Zn–1.77Mg–0.33Fe−0.45Ni (wt pct) alloy bars produced by hot extrusion (HE) followed by radial shear rolling (RSR) and heat treatment (quenching + aging) has been studied. The results show that the suggested thermomechanical treatment (TMT) allows one to produce a specific type of microstructure. HE provides for defect-free deformation of the initial cast structure, while RSR leads to the formation of a fine microstructure due to unique temperature–strain conditions. During deformation, insoluble Al₉NiFe eutectic phase crystals are refined to a size of about 100 nm. These crystals are localized along the grain and subgrain boundaries and act as effective barriers to the migration of high-angle and low-angle grain boundaries. As a result, the formation of a deformed structure with an extensive network of low-angle grain boundaries (especially in the near-surface region where the equivalent strain is about 15) is observed in the central part and in the near-surface region of the obtained bars. The formation of a structure with an average characteristic subgrain size (~ 2 to 3 μm) comparable to that of grains produced by severe plastic deformation processes provides for a favorable combination of mechanical properties (UTS ~ 416 MPa, YS ~ 293 MPa, δ ~ 8.4 pct), which are comparable to the mechanical properties of a similar alloy after equal channel angular pressing.

The construction of the experimental liquidus surface projection and isothermal sections of the Co–V–Zr ternary system was based on the analyses of solidification microstructures and phase constituents. A new compound τ with Cr_0.5Fe_1.5Zr-type was identified, and the measured composition range of Zr in τ was ∼ 28.6 to 57.3 at. pct and 32.9 to 56.8 at. pct at 1100 °C and 1000 °C, respectively. The liquidus surface projection identified nine primary solidification areas, while two primary solidification areas were inferred from binary diagrams. Moreover, eight and ten three-phase equilibria were determined at 1100 °C and 1000 °C, respectively. The measured solubility of V in Co₂₃Zr₆, Co₂Zr and CoZr reached ~ 0.5, 7.6 and 4.1 at. pct at 1100 °C. Meanwhile, the solubility of V in Co₂₃Zr₆, Co₂Zr, CoZr and CoZr₂ was measured to be ~ 0.4, 7.6, 1.6 and 3.6 at. pct at 1000 °C. The solubility of Zr in Co₂V₃ was ~ 3.6 at. pct at 1100 °C, while the solubility of Zr in Co₃V, Co₂V₃ and CoV₃ was determined ~ 1.3, 3.0 and 4.5 at. pct at 1000 °C, respectively. The experimental data can help improve the thermodynamic parameters of the Co–V–Zr system and advance the development of databases for multi-component Co-based superalloys.

In this paper, the tensile properties, texture evolution, and deformation anisotropy of a cold-rolled Fe−0.3C–6.86Mn–3.5Al steel during superplastic deformation at 650 °C–750 °C and 0.25 × 10⁻³ s⁻¹− 4 × 10⁻³ s⁻¹ were studied. In particular, under 750 °C and 1 × 10⁻³ s⁻¹, the anisotropic microstructure evolution and texture characteristics were measured using EBSD. The results indicate that Medium Mn steel (MMS) sheets exhibit significant anisotropy under high tensile stress. The transverse direction (TD) specimens exhibit the highest peak strength of 145 MPa, and rolling direction (RD) specimens exhibit the highest elongation of 1295 pct. The plastic anisotropy r value of the RD sample varied more significantly than that of the TD sample. When the RD sample fractures, the aspect ratio reaches its minimum value (1.52), and ellipse fitting angle (θ) distributes from 0 to 90 degree and from 180 to 90 degree, which indicates that a large number of grains have undergone rotation.

The aim of this study is to evaluate the effect of titanium on the corrosion characteristics of bridge weathering steel plates in marine environments. The corrosion characteristics of steel containing different Ti additions were studied by simulating marine corrosion by cycles of the dry and wet environments. The addition of appropriate amounts of Ti can promote the production of γ-Fe₂O₃, which produces a protective rust layer. Steel containing 0.087 wt pct Ti, gave the best results. During long-term dry/wet cyclic corrosion experiments, the corrosion rate of the #0.087Ti steel first accelerated when a protective product layer has not completely covered the surface. The surface of the #0.087Ti steel was only fully covered after 144 hours of testing. With the further extension of periodic immersion testing the corrosion rate began to decrease gradually. After 576 hours of testing a stable protective product layer formed on the #0.087Ti steel, limiting further corrosion.