As-annealed Alloys Research Articles

Effect of Zr addition on microstructure and properties of Al–Mn–Si–Zn-based alloy

Effects of Zr addition on the microstructure, mechanical and electrochemical properties of Al–Mn–Si–Zn alloy were investigated. Transmission electron microscopy (TEM) observations reveal that, in as-annealled state, the precipitates in the Zr-containing alloy are finer and more dispersive than those in the Zr-free alloy. Whereas, in simulated brazing state, a weaker precipitation is found in the Zr-containing alloy. Tensile testing results indicate that, with Zr additon, comprehensive mechanical properties of the as-annealed alloys could be significantly improved but weakened for the simulated brazing alloy. Electrochemical testing results reveal that, with Zr addition, the corrosion resistance of the as-annealed alloy decreases. However, after the simulated brazing treatment, such a negative effect of Zr element on the corrosion behavior of the alloy could be negligible.

Effect of Nano Grain Growth on Coefficient of Thermal Expansion in Electroplated Fe-Ni Invar Alloy

The aim of this paper is to consider the effect of annealing on the coefficient of thermal expansion (CTE) of electroplated Invar Fe-Ni alloy. The CTE of the as-electroplated alloy is lower than those of alloys annealed at <TEX>$400^{\circ}C$</TEX> and <TEX>$800^{\circ}C$</TEX>. XRD peaks become sharper as the as-electroplated alloy is annealed, which means the grain growth. The average grain sizes of as-electroplated and as-annealed alloys at <TEX>$400^{\circ}C$</TEX> and <TEX>$800^{\circ}C$</TEX> are 10 nm, 70 nm, and <TEX>$2{\mu}m$</TEX>, respectively, as determined by TEM and EBSD analyses. The CTE variation for the various grain sizes after annealing may come from the magnetostriction effect, which generates strain due to changes in the magnetization state of the alloys. The thermal expansion coefficient is considered to be affected by nano grain size in electroplated Fe-Ni Invar alloys. As grain size decreases, ferromagnetic forces might change to paramagnetic forces. The effect of lattice vibration damping of nano grain boundaries could lead to the decrease of CTE.

Effect of Gd and Y contents on the microstructural evolution of long period stacking ordered phase and the corresponding mechanical properties in Mg–Gd–Y–Zn–Mn alloys

This study analyzes the effect of different Gd and Y contents on the microstructural evolution and mechanical properties of Mg–Gd–Y–Zn–Mn alloys. Microstructural analysis indicates the existence of both the long period stacking order and eutectic phases in the as-cast alloys. In case of alloys with high Gd and low Y contents, the main eutectic phase is (Mg,Zn)3(Gd, Y), while in alloys with high Y and low Gd contents, the main eutectic phase is Mg24(Gd,Y,Zn)5. The as-annealed alloys show only α-Mg and LPSO phases; the LPSO phases could be bulk-shaped and lamellar-shaped. The main composition of the LPSO phase with gray bulk-shaped morphology is Mg12ZnY, while the LPSO phase that penetrated thoroughly the grain is mainly Mg12ZnGd. After extrusion, the formation of distorted grains and lamellar-shaped LPSO phases in the alloys with high Gd and low Y contents tends to improve the strength of the as-extruded alloys, while the formation of isometric crystal grains in the alloys with high Y and low Gd contents enhances the alloy elongation.

A comprehensive investigation of structural, morphological, hydrogen absorption and magnetic properties of MmNi4.22Co0.48Mn0.15Al0.15 alloy

A comprehensive study of structural, morphological, hydrogen absorption and magnetic properties of MmNi 4.22 Co 0.48 Mn 0.15 Al 0.15 alloy as a promising hydrogen storage media was investigated. The X-ray diffraction (XRD) profiles show that the alloy maintains its crystal structure (hexagonal LaNi 5-type) even after 30 hydrogenation/dehydrogenation (H/D) cycles. However, the XRD peaks are found to be slightly broadened after cycling. SEM images reveal that particles size of the cycled sample decreases, with more uniform particle size distribution compared to noncycled ones. The pressure-composition (PC) isotherms and kinetics curves of hydrogen absorption reaction were obtained at different working temperatures by using a homemade Sievert apparatus. The enthalpy and entropy of hydride formation of the alloy were evaluated. Furthermore, the Jander diffusion and Johnson–Mehl–Avrami models as the fitting models were employed to study the kinetic mechanism of hydriding reaction and its activation energy. The room temperature magnetic measurements indicate that the milling and H/D cycling change the magnetic properties of the as-annealed alloy.

An investigation on electrochemical performances of as-cast and annealed La0.8Mg0.2Ni3.3Co0.2Si x (x = 0–0.2) alloy electrodes for Ni/MH battery application

The La-Mg-Ni-based A2B7-type La0.8Mg0.2Ni3.3Co0.2Si x (x=0–0.2) electrode alloys were prepared by casting and annealing. The influences of the additional silicon and the annealing treatment on the structure and electrochemical performances of the alloys were investigated systemically. Both of the analyses of XRD and SEM reveal that the as-cast and annealed alloys are of a multiphase structure, involving two main phases (La, Mg)2Ni7 and LaNi5 as well as one minor phase LaNi3. The addition of Si and annealing treatment bring on an evident change in the phase abundances and cell parameters of (La, Mg)2Ni7 and LaNi5 phase for the alloy without altering its phase structure. The phase abundances decrease from 74.3% (x=0) to 57.8% (x=0.2) for the (La, Mg)2Ni7 phase, and those of LaNi5 phase increase from 20.2% (x=0) to 37.3% (x=0.2). As for the electrochemical measurements, adding Si and performing annealing treatment have engendered obvious impacts. The cycle stability of the alloys is improved dramatically, being enhanced from 80.3% to 93.7% for the as-annealed (950 °C) alloys with Si content increasing from 0 to 0.2. However, the discharge capacity is reduced by adding Si, from 399.4 to 345.3 mA·h/g as the Si content increases from 0 to 0.2. Furthermore, such addition makes the electrochemical kinetic properties of the alloy electrodes first increase and then decrease. Also, it is found that the overall electrochemical properties of the alloys first augment and then fall with the annealing temperature rising.

Effect of Homogenization Treatment on Microstructure and Properties of ZnAl15 Alloy

The microstructure, microhardness and corrosion resistance of as-cast and as-annealed ZnAl15 alloys were investigated by OM, SEM, EDX and DSC techniques. It was found that microstructure of as-cast ZnAl15 alloy was primary dendrites and eutectic matrix. But Primary discontinuous precipitation of αs and βs phase occurred at room temperature. During homogenization treatment, discontinuous precipitation of αs and βs phase occurred completely and accompanied with emitting heat. The final microstructures of decomposed αs and βs phase in primary dendrites were fine and coarse lamellar structures respectively. The final microstructures of decomposed βs, which located at the edges of the αs phases or in eutectic matrix were that α phase distributed in η matrix. The microhardness of both primary dendrites and eutectic matrix in ZnAl15 alloys decreased after homogenization treatment due to the decomposition of supersaturated solid solutions. The result of accelerated corrosion test showed that homogenization treatment has a certain beneficial effect on the corrosion resistance of ZnAl15 alloy.

Electrochemical Hydrogen Storage Characteristics of the as-Cast and Annealed La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0∼0.4) Electrode Alloys

Abstract The electrode alloys with the chemical compositions of La 0.8- x Pr x Mg 0.2 Ni 3.35 Al 0.1 Si 0.05 ( x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and annealing. The effects of Pr substitution on the structure and electrochemical hydrogen storage characteristics of the alloys were investigated. The results indicate that the as-cast and the annealed alloys consist of Ce 2 Ni 7 -type hexagonal (La, Mg) 2 Ni 7 phase and CaCu 5 -type hexagonal LaNi 5 phase as well as a little residual phase LaNi 3 . The substitution of Pr for La observably affects the electrochemical hydrogen storage characteristics of the alloys. The discharge capacity and the high rate discharge ability (HRD) of the as-cast and the annealed alloys first increase and then decline with the growing of Pr content. The as-cast and the annealed ( x =0.3) alloys yield the largest discharge capacities of 363.1 and 389.7 mAh/g, respectively. The electrochemical cycle stability of the as-cast and the annealed alloys markedly grows with the rising of Pr content. The capacity retaining rate ( S 100 ) at 100th charging and discharging cycle is enhanced from 64.96% to 77.94% for the as-cast alloy, and from 72.82% to 91.81% for the as-annealed alloy by raising Pr content from 0 to 0.4.

Electrochemical hydrogen storage characteristics of as-cast and annealed La0.8-xNdxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0–0.4) alloys

The La-Mg–Ni–based A2B7-type La0.8-xNdxMg0.2Ni3.15Co0.2Al0.15 (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys were prepared by casting and annealing. The influences of partial substitution of Nd for La on the structure and electrochemical performance of the as-cast and annealed alloys were investigated. It was found that the experimental alloys consist of two major phases, (La, Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure, as well as some residual phase LaNi3 and NdNi5. The discharge capacity and high rate discharge ability (HRD) of the as-cast and annealed alloys first increase and then decrease with Nd content growing. The as-cast and annealed alloys (x=0.3) yield the largest discharge capacities of 380.3 and 384.3 mA·h/g, respectively. The electrochemical cycle stability of the as-cast and annealed alloys markedly grows with Nd content rising. As the Nd content increase from 0 to 0.4. The capacity retaining rate (S100) at the 100th charging and discharging cycle increases from 64.98% to 85.17% for the as-cast alloy, and from 76.60% to 96.84% for the as-annealed alloy.

Structure and electrochemical hydrogen storage characteristics of La0.8−x Pr x Mg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0–0.4) electrode alloys

For the purpose of improving the electrochemical cycle stability of the La-Mg-Ni based A2B7-type electrode alloys, both reducing Mg content and substituting La with Pr were adopted. The La0.8−xPrxMg0.2Ni3.15Co0.2Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4) electrode alloys were fabricated by casting and annealing. The investigation on the structures and electrochemical performances of the alloys was performed. The obtained results reveal that the as-cast and annealed alloys comprise two major phases, (La, Mg)2Ni7 phase with the hexagonal Ce2Ni7-type structure and LaNi5 phase with the hexagonal CaCu5-type structure, as well as a little residual LaNi3 phase. It is also found that the addition of Pr element observably affects the electrochemical hydrogen storage characteristics of the alloys, just as the discharge capacity and high rate discharge ability (HRD) first rise then fall with the growing of Pr content, and among all the alloys, the as-cast and annealed (x=0.3) alloys generate the largest discharge capacities of 360.8 and 386.5 mA·h/g, respectively. Additionally, the electrochemical cycle stability of all the alloys markedly grows with the increase of Pr content. The capacity retaining rate (S100) at the 100th charging and discharging cycle is enhanced from 64.98% to 77.55% for the as-cast alloy, and from 76.60% to 95.72% for the as-annealed alloy by rising Pr content from 0 to 0.4. Furthermore, the substitution of Pr for La results in first increase and then decrease in the hydrogen diffusion coefficient (D), the limiting current density (IL) as well as the electrochemical impedance.

Influence of Zn Content on the Microstructure and Properties of As-Annealed Al-Mn-Si Alloys

The effect of Zn addition on the microstructure, tensile properties and electrochemical properties of as-annealed Al-Mn-Si alloy was investigated through TEM observations, anodization metallography, tensile tests and Tafel polarization analysis. High density precipitates were found in the Zn-containing alloys and the alloy with 1.5 % Zn had the most uniform precipitation. The Zn element could restrain recrystallization of the alloy. Tensile test results indicated that Zn has a great effect on tensile strength of Al-Mn-Si alloy. The alloy with 1.8 % Zn addition had the highest ultimate tensile strength. The electrochemical testing results indicated that Zn element had great impact on the corrosion potential of the as-annealed alloys tested in 0.5% NaCl solutions. Alloying with Zn element could make the corrosion potential shift to negative direction but increase the resistance to pitting corrosion

Effects of annealing treatment on properties of CoCrFeNiTiAlx multi-component alloys

CoCrFeNiTiAlx (x: molar ratio) multi-component alloys were prepared by vacuum arc-melt casting and the as-cast alloys were subsequently heat treated at 1000 °C for 2 h. Effects of Al content and annealing treatment on the mechanical, electrical and magnetic properties were investigated. The addition of Al exhibits significant influence on mechanical properties of the as-cast and the as-annealed alloys, which is actually induced by the evolution of phase composition. The prepared alloys demonstrate good resistance against anneal-softening, as most of the as-annealed alloys show even higher hardness than the as-cast ones. As-annealed Al0 possesses excellent mechanical property with high compressive strength of 2.46 GPa and strain rate of 12.7%. Strengthening mechanism is revalued in this study as phase composition is considered as a critical factor. The as-cast and the as-annealed CoCrFeNiTiAlx alloys exhibit high electrical resistivity and novel magnetic properties as well.

Effects of annealing treatment on phase composition and microstructure of CoCrFeNiTiAl x high-entropy alloys

CoCrFeNiTiAl x ( x: molar ratio) high-entropy alloys with different Al content were prepared by vacuum arc-melt casting and the as-synthesized alloys were subsequently heat treated at 1000 °C for 2 h. Effects of Al content and annealing treatment on phase composition and microstructure of these alloys were investigated by intensive characterization and analysis of the crystal structure, morphology and elemental segregation. Al addition promotes the formation of BCC structured phases in both as-cast and as-annealed alloys. The alloy without Al addition is mainly composed of face-centered cubic (FCC) solid-solution while the main phase transforms to stabilized (α-Fe,Cr)-based body-centered cubic (BCC) solid-solution as Al is introduced. Annealing demonstrates no obvious influence on the main phase and elemental segregation of CoCrFeNiTiAl x alloys except for alloys with low Al content ( x = 0, 0.5 and 1.0) contain more intermetallic compounds after annealing. The phase formation rules of high-entropy alloys is explored in this study as the empirical formation rules of simple solid-solutions are proposed as: mixing entropy (∆S mix) ≥ 13.38 J/K·mol, −10 kJ/mol ≤ mixing enthalpy (∆H mix) ≤ 5 kJ/mol and atom-size difference ( δ) ≤ 4.

Crystallization Behavior and Corrosion Resistance of Cu50Zr40Ag10 Amorphous Alloy

In this study, Cu50Zr40Ag10 amorphous alloy ribbons were prepared by a single roller melt-spinning method. The crystallization behavior of the Cu50Zr40Ag10 amorphous alloy has been investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Moreover, the polarization and passivation behaviors of the as-quenched and as-annealed amorphous alloy have been studied in 1 N H2SO4. The surfaces of corroded samples have been examined using scanning electron microscopy (SEM) and the element distribution across the pits has been analyzed using energy dispersive spectrometer (EDS). The results show that the Cu50Zr40Ag10 amorphous alloy has a large supercooled region up to 36 K. The ω-(ZrCu), ZrO2 and Cu10Zr7 phases can firstly precipitate from the amorphous matrix below glass transition temperature during annealing for 30 min. Moreover, the corrosion resistance of the as-quenched amorphous alloy is better than that of partial and full crystallization products. In addition, Zr plays a crucial role in enriching the passive film and enhancing corrosion resistance.

Annealing effects on structure and mechanical properties of CoCrFeNiTiAlx high-entropy alloys

Novel CoCrFeNiTiAlx(x:molar ratio, other elements are equimolar) high-entropy alloys were prepared by vacuum arc melting and these alloys were subsequently annealed at 1000 °C for 2 h. The annealing effects on structure and mechanical properties were investigated. Compared with the as-cast alloys, there are many complex intermetallic phases precipitated from the solid solution matrix in the as-annealed alloys with Al content lower than Al1.0. Only simple BCC solid solution structure appears in the as-annealed Al1.5 and Al2.0 alloys. This kind of alloys exhibit high resistance to anneal softening. Most as-annealed alloys possess even higher Visker hardness than the as-cast ones. The as-annealed Al0.5 alloys shows the highest compressive strength while the Al0 alloy exhibits the best ductility, which is about 2.6 GPa and 13%, respectively. The CoCrFeNiTiAlx high-entropy alloys possess integrated high temperature mechanical property as well.

Annealing on the structure and properties evolution of the CoCrFeNiCuAl high-entropy alloy

The equiatomic multiprincipal CoCrFeNiCuAl high-entropy alloy was prepared using a vacuum arc melt casting method. The as-cast alloy was subsequently annealed at 1000 °C for 2 h and the annealing effects on the structure and properties evolution were investigated. The as-cast alloy is composed of simple BCC and FCC solid solutions. The “2” FCC phase precipitates from the ordered BCC matrix and the FCC phases become dominated after the alloy was annealed. Both alloys show typical cast-dendrite morphology and similar elemental segregation. The as-annealed alloy exhibits high strength and excellent ductility of 1.63 GPa and 34%, respectively. Both alloys possess high saturated magnetization and undergo a ferromagnetic transition.

Damping behavior and mechanical properties of Mg-Cu-Mn alloy processed by equal channel angular pressing

Equal channel angular pressing(ECAP) was conducted at 250 °C for 4 passes to the as-extruded Mg-3%Cu-1%Mn alloy with high strength and high damping capacity. After ECAP processing, the grain of as-extruded alloy is significantly refined to about 4 μm, both yield strength and tensile strength of the as-extruded Mg-Cu-Mn alloy are decreased, but the ductility is improved. After the ECAP processing, the damping capacity of Mg-Cu-Mn alloy is decreased at room temperature, while is substantially increased at elevated temperatures. After annealing at 300 °C for 1 h, both yield strength and tensile strength of the ECAPed alloy are further decreased, but the ductility is significantly improved. The damping capacity of the as-annealed alloy is increased at room temperature, while is decreased at elevated temperatures. The mechanisms for damping capacity of the alloy at ambient and elevated temperatures were discussed.

Damping characteristics of a Ti 40.5Ni 49.5Zr 10 shape memory alloy

Ti 40.5Ni 49.5Zr 10 alloy undergoes B2 ↔ B19′ martensitic transformation. Damping capacities of B19′ and B2 phases of this alloy are lower than those of Ti 51Ni 49 alloy due to Zr atoms solid-soluted hardening. Transformation temperatures of this alloy decrease, but transformation peak heights Q max − 1 increase with increasing aging time at 300 °C due to the formation of finer (0 0 1) M twins for specimens aged longer. The Q max − 1 peaks of the slightly cold-rolled Ti 40.5Ni 49.5Zr 10 alloy are higher than those of the as-annealed alloy, which may be because the thinner twins are induced by small deformation.

Tensile Deformation and Fracture Behavior of a Commercial Al Alloy with Nano-Sized Grains

The nano-structure in the commercial 5083 Al alloy was introduced by the equal channel angular pressing technique. The nano-sized grains of ~300 nm were obtained after 8 ECAPs at 373 K and 473 K. It was also obvious that much improvement in strength was obtained at lower pressing temperature, 373 K, than 473 K. In particular, there were mainly two different tensile characteristics; one was that the strength in the alloy ECA pressed at 373 K was much higher than that of as-annealed alloy but the elongation to failure was significantly smaller, while, in case of pressing at 473 K, the improvement in strength was found without sacrificing much of the elongation. The other was that the work hardening with increasing the amount of deformation was found in the alloy ECA pressed at 473 K. These tensile deformation characteristics were analyzed based on the observations of microstructure by TEM and fracture surface by FE-SEM.

Microstructural evolution and microhardness of a melt-spun Al–5Ti–1B alloy during annealing

In the present work, microstructural evolution and microhardness of a melt-spun Al–5Ti–1B alloy during annealing have been investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) together with energy dispersive spectroscopy (EDS) and hardness testing. The phases present in the as-annealed Al–5Ti–1B alloy were determined to be α-Al, the equilibrium tetragonal TiAl 3 and hexagonal TiB 2, whereas only α-Al and TiB 2 were identified in the as-spun alloy. Most of Ti in the α-Al solid solution rapidly precipitates by annealing at 500 °C and the low diffusivity of Ti in Al suppresses the coarsening of the TiAl 3 precipitates with prolonged annealing time. Age hardening effect is not observed in the melt-spun Al–5Ti–1B alloy. The microhardness sharply decreases by annealing at 500 °C for 5 min and then slightly changes with prolonged time to 60 min. The microhardness keeps unchanged by annealing at 200 °C for 60 min, while annealing at 300 °C or higher temperatures causes a continuous decrease in microhardness. The microhardness of the as-spun Al–5Ti–1B alloy appears to be governed by a combination of Hall–Petch hardening from the α-Al cell size and solid solution hardening of the α-Al matrix, whereas the microhardness of the as-annealed alloy is mainly governed by a combination of Hall–Petch hardening from the α-Al cell size and particle radius dependent Orowan hardening.

Phase transformation and magnetic properties of Nd–Fe–V–Nb alloys prepared by mechanical alloying

The phase transformation and magnetic properties of the NdFe 11.35− x V x Nb 0.65 ( x=0–1.35) alloys prepared by mechanical alloying (MA) have been studied. Phases of 2:17, 1:7 and 1:12 are formed in the as-annealed alloys with x=0, 0.3–0.7 and 1.0–1.35, respectively. With increasing V content in the NdFe 11.35− x V x Nb 0.65 ( x=0.3–0.7) alloys, the Curie temperatures of the matrix 1:7 phases monotonically increase. Upon nitrogenation, with increasing V content, the intrinsic coercivity μ 0 H c of the nitrided alloys monotonically increases. The increase becomes sharp at x=1.0 due to the formation of a great amount of Nd(Fe, V) 12N δ . The remanence J r and the maximum magnetic energy product (BH) max of the nitrided alloys monotonically decrease with increasing V content. The 1:12 phases are formed in all the NdFe 11− x Nb x V 1 ( x=0, 0.3, 0.65, 1.0) alloys annealed at 850 oC for 20 min. With increasing Nb content, the crystallization of the 1:12 phase is improved and the relative volume fraction of the 1:12 phase tends to be higher. While μ 0 H c of the nitrided alloys monotonically increase, and J r and (BH) max of the nitrided alloys monotonically decrease. With increasing Nb content in the nitrided alloys, the average grain size of α-Fe decrease while the nitrogen content increases.