Effect of the Heat Treatment on the Cube Recrystallization Texture of Al-Mn-Mg Aluminum Alloy

The evolution of the recrystallized structure and texture of a cold-rolled Al-Mn-Mg alloy with different heat treatments was studied. The alloy with dual-heat treatments at 872 K and 644 K (599 °C and 371 °C) exhibited fast recrystallization and had coarser recrystallized grains and stronger cube texture than the alloy with single-heat treatment at 872 K (599 °C). The differences in microstructures and textures were attributed to the precipitation state. Large particles formed during annealing at 872 K (599 °C) played a randomizing effect on the total recrystallization texture, while smaller particles formed during annealing at 644 K (371 °C) not only enhanced recrystallization of the cold-rolled sheets, but also caused formation of coarse, recrystallized grains with a strong cube texture. The evolution of the coarse grains was due to nucleation of cube-oriented grains.     

Effect of Extrusion Temperature on the Plastic Deformation of an Mg-Y-Zn Alloy Containing LPSO Phase Using <Emphasis Type="Italic">In Situ</Emphasis> Neutron Diffraction

The evolution of the internal strains during in situ tension and compression tests has been measured in an MgY₂Zn₁ alloy containing long-period stacking ordered (LPSO) phase using neutron diffraction. The alloy was extruded at two different temperatures to study the influence of the microstructure and texture of the magnesium and the LPSO phases on the deformation mechanisms. The alloy extruded at 623 K (350 °C) exhibits a strong fiber texture with the basal plane parallel to the extrusion direction due to the presence of areas of coarse non-recrystallised grains. However, at 723 K (450 °C), the magnesium phase is fully recrystallised with grains randomly oriented. On the other hand, at the two extrusion temperatures, the LPSO phase orients their basal plane parallel to the extrusion direction. Yield stress is always slightly higher in compression than in tension. Independently on the stress sign and the extrusion temperature, the beginning of plasticity is controlled by the activation of the basal slip system in the dynamic recrystallized grains. Therefore, the elongated fiber-shaped LPSO phase which behaves as the reinforcement in a metal matrix composite is responsible for this tension–compression asymmetry.     

Effects of Pre-tempering on Intercritical Annealing in Fe-2Mn-0.3C Alloy

As-quenched martensite was pre-tempered at 623 K and 923 K (350 °C and 650 °C), and then it reverted to austenite by intercritical annealing at 998 K (725 °C) in a Fe-2Mn-0.3C alloy. Pre-tempering at 623 K (350 °C) accelerates austenite formation, while pre-tempering at 923 K (650 °C) significantly retards it. It is proposed that austenite nucleation is accelerated by increasing the number density and particle size of cementite during tempering, whereas austenite growth is retarded by Mn enrichment in cementite during tempering at high temperature, leading to opposite effects of pre-tempering on reversion kinetics.     

Microstructure and texture evolution of Al during hot and cold rolling

The evolution of microstructure and texture of commercial purity Al during hot and cold rolling has been studied. The results show that the dynamic restoration mechanism for Al rolled to a total equivalent strain of 2.66 at a mean equivalent strain rate of 14.4 s^-1 at 510 °C is essentially dynamic recrystallization (DRX), whereas for those materials deformed to lower strains at lower strain rates at this temperature, the restoration mechanism is mainly dynamic recovery (DRV). This is confirmed by examining the microstructures, textures, and substructures of the material developed during hot rolling as well as by comparing the results with those developed during cold rolling and annealing. The texture analysis using orientation distribution functions (ODFs) indicates that the dynamically recrystallized material has a random orientation distribution, whereas dynamically recovered materials have a developed deformation texture with a predominantD component and a Cu component. The substructure observation by transmission electron microscopy (TEM) indicates that the subgrains in the dynamically recrystallized material are completely dynamically recovered, which is very similar to those subgrains in cold-rolled material. However, the annealed material shows a completely different substructure. By studying all of these structural features, which are closely associated with the dynamic restoration mechanism, it is confirmed that Al undergoes DRX in the present work, which is different from either DRV or static recrystallization (SRX).     

Influence of the Processing Temperature on the Microstructure, Texture, and Hardness of the 7075 Aluminum Alloy Fabricated by Accumulative Roll Bonding

The 7075 alloy is an Al-Zn-Mg-Cu wrought age-hardenable aluminum alloy widely used in the aeronautical industry. The alloy was accumulative roll bonded at 300 °C (573 K), 350 °C (623 K), and 400 °C (673 K), and the microstructure, texture, and hardness were investigated. Cell/(sub)grain size in the nanostructured range, typical β-fiber rolling texture, and homogeneous hardness through thickness were determined in all cases. Misorientation was different at each processing temperature. At 400 °C, the presence of elements in solid solution and the partial dissolution of the hardening precipitates lead to a poorly misoriented microstructure with a high dislocation density and a homogeneous β-fiber texture of low intensity, typical of intermediate degrees of rolling. At 350 °C and 300 °C, highly misoriented microstructures with smaller dislocation density and intense heterogeneous β-fiber rolling texture are observed, especially at 350 °C, wherein the degree of dynamic recovery (DRV) is higher. Hardness of the accumulative roll bonded samples is smaller than that of the starting material due to particle coarsening, and it is affected by solid solution and/or by fine precipitates produced by reprecipitation of the elements in solid solution.     

Deformation Behavior and Evolution of Microstructure and Texture During Hot Compression of AISI 304LN Stainless Steel

Deformation behavior of hot-rolled AISI 304 LN austenitic stainless steel was studied by hot axisymmetric compression tests at 1173 K, 1273 K, and 1373 K (900 °C, 1000 °C, and 1100 °C) at strain rates of 0.01, 0.1, and 1 s^?1. The flow curves were examined to understand the deformation characteristics. The influence of Zener–Holloman parameter was analyzed using appropriate constitutive models. The activation energy for deformation was found to be 473 kJ/mol. Quantitative microstructural analysis was carried out using Electron backscattered diffraction. Compression at 1173 K (900 °C) at all true strain rates gave rise to partially dynamic recrystallized microstructure with strong α-fiber texture. The deformation texture is characterized by the formation of Brass component, and partial dynamic recrystallization (DRX) led to the development of Goss, S, and ube components. Necklace structure of small equiaxed recrystallized grains could be observed surrounding the large, elongated deformed grains. Compressions at 1273 K and 1373 K (1000 °C and 1100 °C) resulted in fully recrystallized microstructure consisting of mostly Σ3 and Σ9 coincidence site lattice high-angle boundaries. Compression at 1273 K (1000 °C) leads to the formation of low-intensity diffused α-fiber. DRX was confirmed by the presence of Goss, S, Cube, and rotated Cube components. Compression performed at 1373 K (1100 °C) resulted in nearly random texture with traces of α-fiber and prominent Cube/rotated Cube components. The microstructures of the 1173 K (900 °C)-compressed samples were partitioned using grain size and misorientation criteria to quantify DRX.     

Texture Evolution During Cross Rolling and Annealing of High-Purity Nickel

Evolution of texture during cross rolling and subsequent annealing was studied in high-purity nickel. For this purpose nickel samples were subjected to multipass cross rolling up to 90 pct reduction in thickness followed by annealing at different temperatures ranging between 673 K and 1073 K (400 °C and 800 °C). Cross rolling was carried out by rotating the samples about the normal direction (ND) by 90 deg interchanging the rolling direction and transverse direction (TD) between each consecutive pass. The development of microstructure and texture was characterized using X-ray and electron backscattered diffraction (EBSD) techniques. The deformation texture was characterized by the presence of strong brass ({110}〈112〉) and ND-rotated brass ({011}〈21 $ \overline{13} $ 13〉)) orientations. Upon annealing at 673 K (400 °C), ND||[111] fiber could be observed in the microtexture which originated from the twin formation of the recrystallized TD-rotated cube ({027}〈0 $ \overline{7} $ 2〉) grains. The fiber was weakened after annealing at 1073 K (800 °C) because of the decreased propensity for twin formation, and the microtexture was found to be weak and diffused. EBSD studies on early recrystallization stages indicated the absence of preferential nucleation of cube grains being in agreement with a weak cube texture formation in annealed cross-rolled high-purity nickel.     

The influence of Sc on thermal stability of a nanocrystalline Al-Mg alloy processed by cryogenic ball milling

The microstructural evolution during annealing of a cryogenically ball-milled Al-7.5Mg-0.3Sc (in wt pct) was examined using differential scanning calorimetry and transmission electron microscopy (TEM). The as-milled alloy was a supersaturated fcc solid solution with an average grain size of ∼25 nm and heterogeneous grain morphologies and size distributions. Calorimetric measurements at a constant heating rate of 32 K/min indicated two exothermic events in association with recovery from 100 °C to 240 °C and recrystallization from 300 °C to 450 °C. Prior to recrystallization, the precipitation of Al₃Sc may occur at low annealing temperatures producing a nonuniform dispersion of approximately spherical particles with diameters of 4 to 5 nm. Recrystallization gave rise to heterogeneous microstructures with bimodal grain size distributions, which may result from the heterogeneity of microstructure in the as-milled state. The heterogeneous microstructures of the recrystallized Al-Mg-Sc alloy were similar to those observed in the recrystallized Sc-free Al-Mg alloy.     

Effects of the Process Parameters on the Microstructure and Properties of Nitrided 17-4PH Stainless Steel

The effects of process parameters on the microstructure, microhardness, and dry-sliding wear behavior of plasma nitrided 17-4PH stainless steel were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wear testing. The results show that a wear-resistant nitrided layer was formed on the surface of direct current plasma nitrided 17-4PH martensitic stainless steel. The microstructure and thickness of the nitrided layer is dependent on the treatment temperature rather than process pressure. XRD indicated that a single α _N phase was formed during nitriding at 623 K (350 °C). When the temperature increased, the α _N phase disappeared and CrN transformed in the nitrided layer. The hardness measurement demonstrated that the hardness of the stainless substrate steel increased from 320 HV_0.1 in the untreated condition increasing to about 1275HV_0.1 after nitriding 623 K (350 °C)/600 pa/4 hours. The extremely high values of the microhardness achieved by the great misfit-induced stress fields associated with the plenty of dislocation group and stacking fault. Dry-sliding wear resistance was improved by DC plasma nitriding. The best wear-resistance performance of a nitrided sample was obtained after nitriding at 673 K (350 °C), when the single α _N-phase was produced and there were no CrN precipitates in the nitrided layer.     

Effect of Annealing on Thermal Stability, Precipitate Evolution, and Mechanical Properties of Cryorolled Al 7075 Alloy

The effect of annealing on microstructural stability, precipitate evolution, and mechanical properties of cryorolled (CR) Al 7075 alloy was investigated in the present work employing hardness measurements, tensile test, X-ray diffraction (XRD), differential scanning calorimetry (DSC), electron backscattered diffraction (EBSD), and transmission electron microscopy (TEM). The solution-treated bulk Al 7075 alloy was subjected to cryorolling to produce fine grain structures and, subsequently, annealing treatment to investigate its thermal stability. The recrystallization of CR Al 7075 alloys started at an annealing temperature of 423 K (150 °C) and completed at an annealing temperature of 523 K (250 °C). The CR Al 7075 alloys with ultrafine-grained microstructure are thermally stable up to 623 K (350 °C). Within the range of 523 K to 623 K (250 °C to 350 °C), the size of small η phase particles and AlZr₃ dispersoids lies within 300 nm. These small precipitate particles pin the grain boundaries due to the Zener pinning effect, which suppresses grain growth. The hardness and tensile strength of the CR Al 7075 alloys was reduced during the annealing treatment from 423 K to 523 K (150 °C to 250 °C) and subsequently it remains constant.     

Structure and Texture of Oxide Dispersion Strengthened Alloy 617 for Very High Temperature Applications

High energy mechanically milled Alloy 617 ODS powder was consolidated by Spark Plasma Sintering (SPS) technique and subsequently annealed at 650 °C and 1050 °C (923 K and 1323 K). Microstructure and microtexture evolution during SPS and annealing have been investigated. SPS consolidated sample exhibited heterogeneous microstructure with ultra-fine grains surrounded by coarse grains. Inhomogeneous distribution of plastic deformation induced during ball milling resulted in heterogeneous nucleation and further grain growth during consolidation. The bimodal microstructure is advantageous with coarse grains providing ductility and fine grains providing strength by the Hall–Petch relationship. The bimodal grains structure was also retained during annealing. As-sintered specimen showed 〈100〉 texture parallel to the compression axis due to dynamic recrystallization during the SPS process. At 650 °C, annealed sample exhibited 〈111〉 annealing texture parallel to compression axis. The texture was randomized in sample annealed at 1050 °C. Precipitation analysis by SEM, XRD and TEM showed the presence of M₂₃C₆, M₆C and Al₂O₃ in both As-sintered and annealed samples. Dispersoids analysis showed the presence of fine and uniform Y₃Al₅O₁₂, Y₄Al₂O₉ and a complex oxide rich in Ni, Y, Al and O. Stress–strain analysis from instrumented indentation test shows higher yield strength for Alloy 617 ODS in comparison with conventional Alloy 617.

     

Clustering and Vacancy Behavior in High- and Low-Solute Al-Mg-Si Alloys

The precipitate microstructure and vacancy distribution in Al-Mg-Si alloys with different amounts of solute and different heat treatments were investigated by transmission electron microscopy and muon spin relaxation measurements. A high amount of vacancies is normally present in Al-Mg-Si alloys as these bind to atomic clusters. We observe these vacancies to leave the material not before over-aging at very high temperatures such as 623 K (350 °C), meaning that vacancies do not bind to incoherent over-aged precipitates. For samples only stored at room temperature after solution heat treatment, a reduction of muon trapping was found at a temperature of 140 K (?133 °C) when reducing the amount of solute in the alloy. This might be connected to a lower number density of Cluster (1), which contrary to Cluster (2) do not nucleate precipitates upon further aging of the material.     

Microstructure Evolution during Recrystallization of Newly Developed Low Ni High Mn‐N Stainless Steels

Low cost stainless steels where nickel is replaced in a conventional Fe‐Cr‐Ni stainless steel by manganese and nitrogen were studied. In this work, three new steels based on the system (mass %) Fe‐18Cr‐15Mn‐2Ni‐2Mo‐XN were prepared and their microstructure after each treatment was evaluated by optical and scanning electron microscopy, and X‐ray diffraction. A good correlation between texture and microstructure evolution during annealing was established. A randomization of the texture during recrystallization of the austenite was observed. Recrystallization starts at temperatures above 850°C, and after annealing for 0.5 h at 900°C, the austenite is completely recrystallized, reaching the orientation density a value near 1. Precipitation of σ ‐ phase was observed in the samples annealed at temperatures ranging from 700 to 950°C.     

Dynamic Recrystallization and Precipitation in 13Cr Super-Martensitic Stainless Steels

The influence of precipitation on the kinetics of static and dynamic recrystallization (DRX) was investigated in AISI 403 and 403Nb martensitic stainless steels. Hot compression tests were performed in the temperature range of 1073 K to 1473 K (800 °C to 1200 °C) and strain rates of 0.001 and 0.1 s^?1 to study DRX and precipitation behaviors. In parallel, stress relaxation tests were conducted with pre-strains of 0.1, 0.15, 0.2, and 0.25, a strain rate of 0.1 s^?1, and in the 1073 K to 1473 K (800 °C to 1200 °C) temperature range to study the kinetics of precipitation and recrystallization. Samples of hot compression and stress relaxation tests were quenched and the evolution of the microstructure was examined using optical and scanning electron microscopy. The results indicated that DRX interacts with dynamic precipitation (DP) over the temperature range of 1173 K to 1273 K (900 °C to 1000 °C). Hot compression testing results, confirmed by EBSD analysis, indicated that partial DRX occurs before precipitation in 403Nb, at 1073 K (800 °C). By contrast, no DRX was observed in 403 steel. At higher temperatures, i.e., over 1273 K (1000 °C), DRX preceded DP in both steels. Increasing the strain rate raised the temperature range of interaction between DRX and DP up to 1373 K (1100 °C). Strain-induced precipitation (SIP) was observed over the entire range of investigated test temperatures. Static recrystallization (SRX) took place predominantly in the temperature range of 1173 K to 1373 K (900 °C to 1100 °C), at which SIP significantly delayed the SRX finishing time. The results are analyzed in the framework of the classical nucleation theory and the underlying mechanisms are identified.     

Texture Evolution of Abnormal Grains with Post-Deposition Annealing Temperature in Nanocrystalline Cu Thin Films

We have examined the evolution of abnormal grain growth texture with increasing post-deposition annealing temperature in nanocrystalline Cu films (20 nm thick) deposited on an amorphous SiN _x (20 nm)/Si substrate. Texture is analyzed by a TEM-based orientation and phase mapping technique based on precession electron diffraction. The as-deposited film, which has an initial grain size of ~12 nm in diameter, already shows a signature of abnormal grain growth, exhibiting a bimodal grain size distribution. Texture is analyzed by calculating area fractions of major components. The overall texture of the as-deposited film is identified to be ??110??, but ??100?? grains occupy the largest fraction in the abnormally grown grain areas, followed by ??111?? grains. After annealing at 398 K, 573 K, and 773 K (125 °C, 300 °C, and 500 °C), the overall texture turns to ??112??. After annealing at 398 K (125 °C), abnormally grown grains have a major ??112?? component. The situation is similar for the film annealed at 573 K (300 °C). After annealing at 773 K (500 °C), the abnormal grain growth texture evolved into major ??111??. The ??100?? component found in the abnormal grain growth texture for the as-deposited film is clearly explained by elastic strain energy minimization and the ??111?? component for the as-deposited film and the film annealed at 773 K (500 °C) is explained by surface energy minimization. The development of the ??112?? texture obtained after annealing at 398 K and 573 K (125 °C and 300 °C) is not explained by either elastic strain energy minimization or surface energy minimization. We suggest that it is clarified by assuming that the Cu film system is perfectly elastic?Cplastic, which is associated with the Taylor factors.     

Aging Effect on Texture Evolution during Warm Rolling of ZK60 Alloys Fabricated by Twin-Roll Casting

ZK60(Mg-Zn-Zr) alloys experience variation of precipitates during aging. The frequency and size of rod- and disk-shaped precipitates change with aging. The effect of aging on texture evolution during warm rolling of ZK60 was investigated. Some difference was found between the texture evolution of solution heat-treated (T4) and artificially aged (T6) samples. The Aged samples had more texture variations along the thickness direction than solution heat-treated samples. The intensities of basal fibers were lower during asymmetric rolling than during symmetric rolling, although the initial intensities increased during both rolling processes. The decrease in basal fibers by asymmetric rolling was clearer at a lower temperature of 448 K (175 °C) than at 498 K (225 °C).     

Microstructural Changes by Annealing in Ultrafine-Grained Electrodeposited Pure Iron

In situ neutron diffraction during annealing was performed for ultrafine-grained as-deposited and cold-rolled pure iron. Changes in the integrated intensity and full-width at half-maximum in the diffraction profiles during annealing were measured. EBSD measurements were performed before and after annealing to obtain microstructural change. Abnormal grain growth was clearly found at 673 K (400 °C) upon annealing; this observation corresponds to the hydrogen desorption behavior of the as-deposited specimen. The texture changes from {111}〈hkl〉 to {211}〈hkl〉 between 673 K and 873 K (400 °C and 600 °C) upon continuous heating. Such a texture change is postulated to decrease the Lankford value from 7.6 to 2.2. The 40 pct cold-rolled specimen exhibited a complicated textural evolution upon annealing, which was caused by the intrusion of recrystallization at deformation bands.     

Evolution of Microstructure and Texture During Warm Rolling of a Duplex Steel

The effect of warm rolling on the evolution of microstructure and texture in a duplex stainless steel (DSS) was investigated. For this purpose, a DSS steel was warm rolled up to 90 pct reduction in thickness at 498 K, 698 K, and 898 K (225 °C, 425 °C, and 625 °C). The microstructure with an alternate arrangement of deformed ferrite and austenite bands was observed after warm rolling; however, the microstructure after 90 pct warm rolling at 498 K and 898 K (225 °C and 625 °C) was more lamellar and uniform as compared to the rather fragmented and inhomogeneous structure observed after 90 pct warm rolling at 698 K (425 °C). The texture of ferrite in warm-rolled DSS was characterized by the presence of the RD (〈011〉//RD) and ND (〈111〉//ND) fibers. However, the texture of ferrite in DSS warm rolled at 698 K (425 °C) was distinctly different having much higher fraction of the RD-fiber components than that of the ND-fiber components. The texture and microstructural differences in ferrite in DSS warm rolled at different temperatures could be explained by the interaction of carbon atoms with dislocations. In contrast, the austenite in DSS warm rolled at different temperatures consistently showed pure metal- or copper-type deformation texture which was attributed to the increase in stacking fault energy at the warm-rolling temperatures. It was concluded that the evolution of microstructure and texture of the two constituent phases in DSS was greatly affected by the temperature of warm rolling, but not significantly by the presence of the other phase.     

Microstructure and Mechanical Behavior of Powder Metallurgy Mg98.5Gd1Zn0.5 Alloy

The Mg_98.5Gd₁Zn_0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg₃Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.     

Metastable β-type Ti-30Nb-1Mo-4Sn Alloy with Ultralow Young’s Modulus and High Strength

The effect of thermo-mechanical treatment on the mechanical properties of a novel metastable β-type Ti-30Nb-1Mo-4Sn (wt pct) alloy has been investigated. The solution-treated alloy consists of β and α″ phases and exhibits a two-stage yielding with a low yield stress (around 100 MPa). After cold rolling at a reduction of 87.5 pct and subsequent annealing treat at 623 K (350 °C) for 30 minutes, a fine microstructure with nano-sized α precipitates distributed in small β grains as well as high density of dislocations was obtained to achieve a yield strength of 954 MPa and an ultimate tensile strength of 999 MPa. With low stability of β phase and small volume fraction of α precipitates, the annealed specimen exhibits a low Young’s modulus of 45 GPa. Such an excellent combination of the low elastic modulus and high strength in mechanical properties indicates a great potential candidate for biomedical applications.