Hot-rolled Alloy Research Articles

Synergistic effect of B2 phase and O phase in hot-rolled Ti2AlNb alloy and its influences on mechanical properties

The Ti2AlNb alloy, solution-treated at 1070 °C, underwent hot rolling at 960 °C with different thickness reductions to investigate the synergistic effects of the O phase and B2 phase and their impact on its properties. The results reveal that after solution treatment, the Ti2AlNb alloy consists of nearly spherical O, lath O, and B2 matrix at 30% and 50% thickness reductions during hot rolling. However, at a 70% thickness reduction, the alloy exhibits spherical O, worm-like O, and a continuously distributed B2 phase. The α2 phase formed during solution treatment decomposes during hot rolling. As the thickness reduction increases from 30% to 70%, the O phase content initially rises and then declines, accompanied by an increase in the average dimension of the O phase from 0.25 ± 0.16 μm to 0.36 ± 0.18 μm. Additionally, the B2 phase in the alloy undergoes dynamic recrystallization (DRX) during hot rolling, coinciding with the growth and spheroidization of the O phase. With an increase in the thickness reduction during hot rolling, the elongation of the alloy increases from 5.9% at 30% reduction to 12.47% at 70% reduction. Meanwhile, the ultimate tensile strength reaches its peak value of 1092.2 MPa at 30% reduction, decreases to 936 MPa at 50%, and then increases to 970 MPa at 70%. The tensile strength of the alloy improves due to the interaction and accumulation of dislocations at the phase interface. The continuous distribution of the B2 matrix, dislocation movement, rotation of the O phase, DRX of the B2 phase, and interface slip all contribute to enhanced ductility. Furthermore, the fracture behavior of the Ti2AlNb alloys under various hot rolling conditions was elucidated.

Evolution of microstructure, mechanical properties, and corrosion behavior of Al-xMg-Mn alloy plates by rolling treatment

This article presents a systematic study on the synergistic effects of Mg element and rolling on the microstructure, mechanical properties, and corrosion resistance of Al-Mg-Mn alloy. The presence of Mg element leads to the formation of the β-phase (Al3Mg2). In the as-rolled alloy with high Mg content, the continuity of β-phase distributed at grain boundaries or fiber texture boundaries is weakened and its size is refined. This refinement is beneficial for improving the hardness and tensile properties of the alloy. However, it slightly reduces the electrical conductivity, elongation, and corrosion resistance of the alloy. The reasons for these changes in properties are analyzed from the perspective of dislocation motion. Comparing the hot-rolled state alloy with the cold-rolled state alloy, it is found that the corrosion resistance of the latter is improved. This improvement can be attributed to the difficulty of forming a continuous network of β-phase at grain boundaries, which significantly reduces the alloy's corrosion sensitivity. Additionally, the higher strength of the alloy can be attributed to dispersion strengthening and grain boundary strengthening. The objective of this work is to provide a strategy for obtaining Al-Mg-Mn alloy sheets with excellent performance

A comparative study on the effect of 0.5 wt% Ca or Ce on the microstructure, texture, and mechanical properties of the hot-rolled Mg-4Li alloy

The microstructure, texture, and mechanical properties of the hot-rolled Mg-4Li, Mg-4Li-0.5Ca and Mg-4Li-0.5Ce alloy were examined. The results indicated that the addition of either Ca or Ce significantly refined the microstructure and largely randomized the texture distribution of as-rolled Mg-4Li. Meanwhile, Mg-4Li-0.5Ca exhibited a relatively smaller grain size and a more scattered texture distribution compared to Mg-4Li-0.5Ce, probably attributed to the more prominent recrystallization in Mg-4Li-0.5Ca. Additionally, owing to the more refined microstructure and dispersed Mg2Ca, the strength of Mg-4Li-0.5Ca is much higher than that of Mg-4Li-0.5Ce, while both of them are superior to the counterpart of Mg-4Li. Moreover, by benefiting from the enhanced activation of non-basal slip, Mg-4Li-0.5Ce exhibits a much larger elongation compared to Mg-4Li. However, the elongation of Mg-4Li-0.5Ca is slightly lower than that of Mg-4Li, potentially ascribed to the occurrence of preferred cracking within the eutectic-like Mg2Ca.

Role of loading direction on high-temperature tensile behavior of Fe-13Cr-4Al-2Mo-0.65Nb alloy

The Fe-13Cr-4Al-2Mo-0.65Nb alloy is being considered as a promising accident-tolerant cladding fuel material for light water reactors design. The present work investigated the mechanical properties and serration behavior of the hot-rolled FeCrAl alloy in the rolling direction (RD) and transverse direction (TD) under various temperatures. The presence of the high-density dislocation bands parallel to RD and the smaller grain size in TD are recognized as leading causes of the lower ductility of the TD specimens. Additionally, both RD and TD specimens show identical serrated flow behaviors at each temperature, suggesting the serration behavior is independent of the loading direction.

Corrosion behavior and mechanical properties of hot-rolled ultrahigh-strength steel alloys in alkaline and acidic environments

The corrosion behavior and mechanical properties of three hot-rolled ultrahigh-strength steel (UHSS) in alkaline (pH 11) and acidic (pH 5) environments were investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. Results were analyzed in terms of the corrosion potential, corrosion current density, impedance modulus, and phase angle. The effect of amount and distribution of ferrite, bainite and cementite, as well Mo, and V alloys percentage content was assessed. The results of electrochemical techniques indicated that main type of corrosion was continuous anodic dissolution with a passivation tendency; this corrosion behavior was driven by charge transfer, charge concentration, and activation polarization. The redox reactions and the type of corrosion products, along with the Mo and V contents, determined the behaviors of the impedance modulus and the phase angle mainly due to the effect of galvanic micro-pairs. The hot-rolling process does not significantly alter the mechanical properties of the as-prepared steels. However, the corrosion current density of alloys is reduced. The UHSS with the highest corrosion resistance and best mechanical properties in both solutions was the L3 alloy.

Mechanical properties and corrosion behavior of electron beam cold hearth melting high strength and high corrosion resistant Ti-0.3Mo-0.8Ni alloy with different states

In this study, a large size Ti-0.3Mo-0.8Ni (TA10) alloy ingot melted by electron beam cold hearth melting (EBCHM) technology was investigated. The microstructure, mechanical properties, and corrosion behavior of as-cast, hot-rolled, and annealed TA10 alloys were investigated. The results show that different states of TA10 alloys have different microstructure and properties. The microstructure of the as-cast TA10 alloy exhibits the Widmanstätten α phase, and the hot-rolled TA10 sheet shows a fibrous structure with an obvious rolling streamline. After 650 °C annealing, the intergranular β phase decreases, and most of the strip α phase changes to the equiaxed α phase. With the annealing temperature increasing to 840 °C, the microstructure gradually changed from an equiaxed structure to a duplex structure. The mechanical properties of the TA10 alloy were enhanced after hot-rolling with an increase in ultimate tensile strength from 386.5 MPa to 610 MPa. Additionally, the elongation increased from 15.6 % to 23.3 %. Upon annealing at varying temperatures, it was observed that the strength decreased, reaching to 423.5 MPa at 650 °C and 478.2 MPa at 840 °C, while the plasticity increased significantly, reaching to 26.5 % at 650 °C and 28.6 % at 840 °C. The improved strength was attributed to the better grain boundary slip of the equiaxed structure. The corrosion resistance of titanium alloys is closely connected with their microstructure. The results of the immersion corrosion test indicate that the samples in various states exhibit similar corrosion behavior. Additionally, the hot-rolled TA10 alloy shows the highest corrosion resistance, with a lower corrosion rate of 0.34459 mm/year. The as-cast TA10 alloy shows the lowest corrosion resistance, with a lower corrosion rate of 1.37559 mm/year.

On the effect of high-temperature annealing on the microstructure and mechanical properties of a hot-rolled 90W7Ni3Fe tungsten heavy alloy

We previously reported on commercial 90W7Ni3Fe (90W, wt. %) tungsten heavy alloy (WHA) plates, which were hot-rolled (HR) at 900 °C to thickness reductions of 62 %, 74 % and 87 % (62R, 74R and 87R), and an as-sintered (AS) 90W plate. In contrast to 62R and 74R, the 87R WHA was given a final processing heat treatment (HT) at 1400 °C/3 h (87RHT). HR deforms the WHA microstructure into an anisotropic brick (W) and mortar (NiWFe ductile phase) composite architecture. Fracture toughness tests showed that after the processing HT, the 87RHT plate experienced stable crack growth, with an average elastic-plastic fracture toughness of KJm ≈ 116 ± 20 MPa√m, somewhat higher than the AS KJm ≈ 97 ± 18 MPa√m. This compares to elastic fracture toughness of KIm ≈ 35 ± 2 MPa√m in the 62R and 74R conditions, absent a final HT. Here, we report on the microstructures and mechanical properties of four new WHA conditions following an additional recovery anneal at 1300 °C/24 h. The recovery anneal results in similar average elastic-plastic toughness of KJm ≈ 125 ± 12 MPa√m in all four processing conditions, which is slightly higher than for the AS and 87RHT WHA, and much higher than for the 62R and 74R WHA, without the processing HT. Scanning electron microscopy and electron backscatter diffraction showed that the final 1300 °C/24 h anneal recovers the hardening microstructures in the 62R and 74R WHA. The lower strength promotes crack tip microcracking dilatational shielding, which increases the WHA fracture toughness. The implications of these results to the design of WHA are briefly discussed.

Effect of Zr addition on the microstructure and mechanical properties of hot-rolled TiZrAlSn alloys

In this study, the microstructure and mechanical properties of hot-rolled χZr-Ti-5Al-2.5Sn (χ = 0, 10, 20, 30 and 35, wt%) alloys were systematically investigated. With the increase of Zr addition, phase constitutions of TiZrAlSn alloys change from single α phase to α + α´, α´ and α´ + αʺ + β phases in sequence while the β transformation temperature decreases. A lower content of α”+β phases appears in the 35Zr-Ti-5Al-2.5Sn alloy. The yield strength of TiZrAlSn alloys increased monotonically from 612 ± 15 MPa for basal Ti-5Al-2.5Sn alloy to an ultra-high strength of 1386 ± 11 MPa for 35Zr-Ti-5Al-2.5Sn alloy, which is ∼126% higher than that of basal alloy. The high content of Zr solute atoms, high density of dislocations and interfaces/boundaries in α´ martensite phase render the ultra-high yield strength and high strain hardening rate in 35Zr-Ti-5Al-2.5Sn alloy. With respect to ductility, the uniform and total elongations increase initially from Ti-5Al-2.5Sn alloy to 10Zr-Ti-5Al-2.5Sn alloy and decrease afterward until 35Zr-Ti-5Al-2.5Sn alloy. The bimodal microstructure of primary α grains and secondary α´ martensite (βtrans region) rendered 20Zr-Ti-5Al-2.5Sn alloy the best comprehensive mechanical properties which included the tensile strength of 992 ± 11 MPa, total elongation of 17.2 ± 1% and a high strain hardening rate. This high strain hardening ability of 20Zr-Ti-5Al-2.5Sn alloy comes from the compatible deformation of soft primary α and hard secondary α´ martensite phases with high density of dislocations and boundaries. In addition, the 20Zr-Ti-5Al-2.5Sn alloy shows a high elongation during tensile necking. The corresponding ductile fracture morphologies of TiZrAlSn alloys are also analyzed. These high-strength TiZrAlSn alloys could be helpful for developing novel TiZr alloys with a high strength and ductility.

Effects of Friction Stir Processing on the Microstructure and Mechanical Properties of an Ultralight Mg-Li Alloy

Magnesium–lithium alloys are arguably the lightest metal structural materials but have low strength. In order to increase strength, friction stir processing (FSP) is applied to a hot-rolled Mg-10Li-3Al-3Zn (LA103Z) sheet to study the effects on the microstructure and mechanical properties. In this study, the strengthening mechanisms of various FSP regions of an Mg-Li alloy were clarified by a combination of numerical simulation and experimental method. Based on ANSYS APDL, a finite element model with a moving heat source is established. Rotational speeds of 800, 1000, and 1200 rpm and traverse speeds of 100, 110, and 120 mm/min were used in this research. The simulation results confirm that the influence of the rotation speed on the alloy temperature field is greater than that of the travel speed. The temperature of the processing area increases with an increase in rotation speed and decreases with an increase in travel speed. Then, hot-rolled LA103Z alloy plates are processed by FSP. The correspondence between the numerical simulation and experiment was verified by infrared thermography. The results indicate that FSP decreases the grain size significantly for the dynamic recrystallization and dramatic mechanical crushing of the stirring pin. The α-Mg and AlLi are solid soluted in the β-Li matrix. The tensile strength of the processing zone is 260.67 MPa (1000 rpm, 110 mm/min) versus the 170.47 MPa of the base metal. The SZ has the highest microhardness of 77.8 HV (800 rpm, 120 mm/min) and decreases gradually to the BM. The severe deformation, recrystallization, and solid solution of the α-Mg are important factors contributing to the improved mechanical properties.

Distinctive fatigue properties of additively-formed CoCrFeNiTiMo multi-principal element alloy: Excellent fatigue crack growth resistance against ordinally high cycle fatigue strength

In this study, the fatigue characteristics of additively-formed multi-principal element alloy (MPEA) of Co1.5CrFeNi1.5Ti0.5Mo0.1 (CoCrFeNiTiMo alloy) were systematically compared with conventional hot-rolled and additively-formed Alloy 718 nickel-based super alloy, which have comparable mechanical properties. Evaluated fatigue properties were the low-to high-cycle fatigue strengths of plane and notched specimens, and long/short fatigue crack growth (FCG) resistance. The results showed the fatigue strength of CoCrFeNiTiMo alloy to be comparable to that of Alloy 718 for smooth specimens, while the fatigue strength of notched specimens was 50% higher. Superior notch fatigue strength can be quantitatively explained in terms of outstanding long fatigue crack growth resistance. Regardless of load ratio, CoCrFeNiTiMo exhibits superior FCG resistance that greatly surpasses that of conventional Fe and Ni alloys. In contrast, the short FCG resistance of CoCrFeNiTiMo was comparable to that of Alloy 718, which corresponds to the fatigue strength level of a smooth specimen. Investigation of fatigue fracture surface and microscopic slip deformation morphology around the fatigue crack indicates that CoCrFeNiTiMo alloy exhibits more planar slip deformation than Alloy 718. Slip constraint stimulated by slip planarity appears to have an important role in short and long FCG resistance when cracks cross grain boundaries.

Microstructural evolution, high temperature tensile deformation behavior, and deformation mechanism in an Mg–Zn–Y–Ca–Zr alloy processed by multidirectional forging and hot rolling

To explore high temperature ductility, a new Mg-2.70Zn-1.34Y-0.37Ca-0.02Zr (wt.%) alloy has been fabricated by novel multidirectional forging (MDF) and hot rolling. The microstructure and mechanical properties were investigated. The average grain size of MDF + hot rolled alloy is 10.89 ± 0.90 μm refined from the as-cast average grain size of 60.03 ± 0.72 μm. The ultimate tensile strength of 260.51 ± 1.03 MPa, yield strength of 192.29 ± 1.21 MPa, and elongation of 17.83 ± 0.72 % were obtained at room temperature. For high temperature tensile behavior, microstructural examination revealed that continuous dynamic recrystallization and discontinuous dynamic recrystallization are the main softening mechanism in the temperature range of 573–673 K, while dynamic grain growth with bimodal grains and twins is discovered at 723 K in this alloy. X-ray diffraction and scanning electron microscopy –energy dispersive spectroscopy examinations revealed that the constituent phases are composed of α-Mg solid solution and intermetallic compounds of Ca2Mg6Zn3, Mg3YZn6 (I-phase), and Mg3Zn3Y2 (W-phase). The microstructural evolution, such as dynamic recrystallization and dynamic grain growth at desired tensile temperatures, is related to the thermal stability of constituent phases. The elongation to failure of 215.4 % was demonstrated at 673 K and 1.67 × 10−2 s−1, exhibiting high strain rate quasi-superplasticity. A power-law constitutive equation was established. The deformation activation energy of 177.948 kJ/mol and stress exponent of 4.494 revealed that the dominant deformation mechanism of this alloy at elevated temperatures of 573–723 K is dislocation climb controlled by lattice diffusion.

Effect of rolling reduction on the microstructure and mechanical properties of hot-rolled Mg-Li-Al-Ca alloys

To improve the strength of magnesium (Mg)-lithium (Li) alloy without sacrificing plasticity, Mg-7.3Li-4Al-3Ca alloy is designed and subsequently rolled at 350 °C. The microstructure evolution and mechanical properties of the alloy under different rolling reductions are studied. The results show that the as-cast and hot rolled alloy is composed of α-Mg, β-Li matrix phases as well as Al2Ca and (Mg, Al)2Ca precipitated phases. After hot rolling, the agglomerated Al2Ca precipitates are broken and dispersed in the matrix. A large amount of continuous filamentous (Mg, Al)2Ca phase becomes discontinuous and the phase content decreases monotonously with increasing rolling reduction due to the decomposition of (Mg, Al)2Ca phase and the corresponding constituent elements dissolve in the matrix. During the hot-rolling process, some fine equiaxed grains appear in the alloy matrix due to dynamic recrystallization. Both the strength and elongation of Mg-7.3Li-4Al-3Ca alloy increases monotonously with increasing rolling reduction. For the alloy with rolling reduction of 60%, the ultimate tensile strength and elongation are 218Mpa and 24.8%, respectively, which are 52.4% and 153% higher than those for the as-cast alloy. The strengthening mechanism is attributed to fine grain strengthening, precipitation strengthening and solid solution strengthening. Grain refinement and the appropriate distribution of Al2Ca and (Mg, Al)2Ca phases causes the obvious increase of the plasticity.

Influence of Gd and Li additions on the microstructural evolution and mechanical properties of hot-rolled AZ31 alloy

Thermomechanical processing and alloying are two common approaches to enhance the mechanical properties of Mg. Thus, the effects of Gd and Li elements, as two elements with various properties, on the microstructure and mechanical properties of a hot-rolled and consequently annealed AZ31 alloy were analyzed. The microstructure and texture was analyzed by scanning electron microscopy and electron back scattered diffraction. Accordingly, the mean grain size of 46 μm in the AZ31 alloy was reduced to 41 and 26 μm in the AZ31–2.9Gd and AZ31–2.3Li alloys, respectively. Grain refinement occurred due to continuous dynamic recrystallization and twinning-induced recrystallization in all of the alloys. Textural evolution showed that neither Gd nor Li could inhibit the occurrence of basal texture. Room temperature mechanical properties were assessed by using the shear punch test (SPT) method. The results exhibited that the strength of the AZ31 alloy was improved from 116 MPa to 139 MPa and 141 MPa by respective additions of Gd and Li. Strength enhancement was mainly attributed to the grain boundary strengthening and second-phase particles hardening. One promising observation was the simultaneous enhancement of shear strength and ductility by the addition of Gd and Li. This observation was ascribed to the more uniform distribution of second-phase particles and lower volume fraction of twins as potential sites for crack initiation. As long as mechanical strength is concerned, results favor the use of Li as alloying element in Mg, especially due to the more noticeable lightweighting potential compared to Gd.

Internal Elastic Strains of AZ31B Plate during Unloading at Twinning-Active Region

Magnesium alloys, being the lightest structural metals, have garnered significant attention in various fields. The characterization of inelastic behavior has been extensively investigated by researchers due to its impact on structural component performance. However, the occurrence of twinning in the absence of any applied driving force during unloading has lacked reasonable explanations. Moreover, the influence of deformation mechanisms other than twinning on inelastic behavior remains unclear. In this study, uniaxial tension and compression tests were conducted on hot-rolled magnesium alloy plates, and neutron diffraction experiments were employed to characterize the evolution of macroscopic mechanical response and microscopic mechanisms. Additionally, a twinning and detwinning (TDT) model based on the elastic visco-plastic self-consistent (EVPSC) model has been proposed, incorporating back stress to describe the deformation behavior during stress relaxation. This approach provides a comprehensive understanding of the inelastic behavior of magnesium alloys from multiple perspectives and captures the influence of microscale mechanisms. A thorough understanding of the inelastic behavior of magnesium alloys and a reasonable explanation for the occurrence of twinning under zero-stress conditions offer valuable insights for the precise design of magnesium alloy structures.

Microstructure and mechanical behaviour of Nb- containing high Al ferritic low density steels

Two high Al ferritic low density steels, Fe-11Al-5Mn-1Nb-1C (Alloy 1) and Fe-11Al-10Mn-1Nb-1C (Alloy 2) were prepared by vacuum induction melting. Their recrystallization behaviour is investigated. Hot rolling of the steels was carried out at 1100 °C. The temperature was chosen to ensure that the alloys were hot rolled in the intercritical region. Hot rolling led to a ferritic microstructure which was only partially recrystallized even after 92% rolling reduction. Annealing of hot rolled alloys at 1000 °C for 1 h results in a significant Static Recrystallization of the ferrite matrix. This suggests that dynamic recrystallization is difficult in these high Al ferritic steels. A further reduction of 33% was given to the hot rolled and annealed alloys by cold rolling. Annealing of cold rolled alloys at 1000 °C for 1 h leads to almost complete recrystallization. The hot rolled alloys exhibit better Yield and Ultimate Tensile Strength whereas the annealed alloys show higher total elongation. The best combination of properties is obtained in cold rolled and annealed samples. Alloy 2 exhibit superior tensile properties in comparison to Alloy 1. NbC precipitates pin the grain boundaries and may delay recrystallization. This necessitates further cold working and annealing to achieve complete recrystallization. NbC precipitates result in a significant refinement in grain size in annealed alloys. Nb addition also permits cold rolling without edge cracking. Thus, Nb may be an important alloying addition for high Al ferritic low density steels.

Microstructure and Texture Evolution of Hot-Rolled Mg-3Gd Alloy during Recrystallization

An Mg-3Gd (wt.%) sample with gradient rolling strains (ε = 0–0.55) was prepared using a wedge-shaped plate after one-pass hot rolling, allowing a high-throughput characterization of microstructure and texture over a wide strain range within one hot-rolled plate. The microstructure and texture evolutions were characterized as a function of rolling strain for the as-hot-rolled sample and as a function of annealing temperature for the subsequently annealed samples. The deformed microstructure showed a gradual change with increasing rolling strain, i.e., from a deformation twins-dominant structure in the low strain range of 0–0.20, to a shear bands-dominant structure in the higher strain range of 0.20–0.55. The recrystallization behavior during annealing showed a clear correlation between the recrystallization nucleation site and the deformed microstructure. However, a weak recrystallization texture with non-basal texture components was formed over almost the entire strain range. This work demonstrates a high-throughput experimental strategy using a wedge-shaped sample to investigate the effect of various processing parameters, such as strain and annealing temperature, on the evolution of microstructure, texture, and mechanical properties, which could accelerate the optimization of processing parameters and microstructural design.

Strength and Toughness of Hot-Rolled TA15 Aviation Titanium Alloy after Heat Treatment

To investigate the impact of various heat treatments on the strength and toughness of TA15 aviation titanium alloys, five different heat treatment methods were employed in the temperature range of 810–995 °C. The microstructure of the alloy was examined using a scanning electron microscope (SEM) and X-ray diffraction (XRD), and its mechanical properties were analyzed through tensile, hardness, impact, and bending tests. The findings indicate that increasing the annealing temperature results in an increase in the phase boundary and secondary α phase, while the volume fraction of the primary α phase decreases, leading to a rise in hardness and a decrease in elongation. The tensile strength of heat-treated samples at 810 °C was notably improved, displaying high ductility at this annealing temperature. Heat treatment (810 °C/2 h/WQ) produced the highest tensile properties (ultimate tensile strength, yield strength, and elongation of 987 MPa, 886 MPa, and 17.78%, respectively). Higher heat treatment temperatures were found to enhance hardness but decrease the tensile properties, bending strength, and impact toughness. The triple heat treatment (810 °C/1 h/AC + 810 °C/1 h/AC + 810 °C/1 h/AC) resulted in the highest hardness of 601.3 MPa. These results demonstrate that various heat treatments have a substantial impact on the strength and toughness of forged TA15 titanium alloys.

Tribological behavior of boronized Fe40Mn20Cr20Ni20 high-entropy alloys in high temperature

Boronization can improve the wear resistance of high-entropy alloys (HEAs). However, the tribological tests on boronized HEAs were generally carried out at room temperature. In fact, materials are often applied in high temperature. Therefore, it is essential to investigate the effect of boronization on the tribological properties and mechanism of HEAs in high temperature. In present work, the hot-rolled Fe40Mn20Cr20Ni20 HEAs were boronized by the pack cementation method at 900 °C for 6 h. The tribological tests of the alloys before and after boronization were conducted in 20–600 °C. The results showed that the boronized alloys showed higher wear resistance at 20–600 °C, whose average coefficients of friction and wear rate were lower than those of hot-rolled alloys. At 20–200 °C, the main wear mechanisms of the hot-rolled alloys were abrasive and adhesive wears; while the main wear mechanism of the boronized alloys was polishing effect. At 300–600 °C, the main wear mechanisms of the alloys before and after boronization were oxidation and abrasive wear. The wear rate was reduced by the B2O3 produced on the surface of the boronized layer during wear and the good thermal stability of the boronized layer, which indicated that boronization improved the wear resistance of HEAs in high temperature.

Effect of Rolling Reduction on Microstructures and Mechanical Properties of Sc-Containing Al-3.2Cu-1.5Li Alloy

The effects of various rolling reductions (64.7%, 72.1%, 81.4% and 88.2%) on the microstructures and mechanical behaviors of Sc-containing Al-3.2Cu-1.5Li-based alloys were experimentally investigated through XRD, SEM (equipped with EBSD), TEM and the tensile test. The results showed that the grains of hot-rolled and T6-treated alloys are mainly dominated by substructure features, and the addition of the trace Sc element can obviously impede the static and dynamic recrystallization due to the formation of fine and stable nano-Al3(Sc, Zr) particles. Additionally, the combined effects of fine grains, dispersion, substructure and precipitation strengthening make the alloys with a rolling reduction of 81.4% possess higher tensile properties. With an increase in the rolling reduction, the tensile strength of the alloys increases first and then decreases, while the elongation gradually increases and then reaches a plateau, which was ascribed to the variation in the grain size and substructure features.

Recrystallization of Hot-Rolled 2A14 Alloy during Semisolid Temperature Annealing Process.

In this study, in order to provide proper parameters for the preparation of semisolid billets, the semisolid annealing of hot-rolled 2A14 Al alloy was investigated. The microstructure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an X-ray energy dispersive spectrometer (EDS) and electron backscattered diffraction (EBSD), and scanning transmission electron microscopy (STEM). The XRD results showed that, with an increase in temperature, the θ-Al2Cu equilibrium gradually dissolved in the matrix. The EDS results of SEM and STEM showed a coarse θ-Al2Cu phase, ultrafine precipitate Al(MnFeSi) or (Mn, Fe)Al6 phase, and atomic clusters in the microstructure. The EBSD results showed that the recrystallization mechanism was dominated by continuous static recrystallization (CSRX), homogeneous nucleation occurred when the sample was heated to near solidus temperature, and CSRX occurred at a semisolid temperature. In the process of recrystallization, the microtexture changed from the preferred orientation to a random orientation. Various experimental results showed that static recrystallization (SRX) occurred at a semisolid temperature due to the blocking effect of atomic clusters on the dislocation slip, and the Zener drag effect of fine precipitates on low-angle grain boundaries (LAGBs) disappeared with melting at a semisolid temperature.