Effect of the Growth Velocity on Microstructure, Orientation, and Magnetostriction in Fe81Ga19 Alloy

Polycrystalline Fe₈₁Ga₁₉ rods were directionally solidified by an induction heating zone melting method at different growth velocities. The microstructure, preferred orientation, and magnetostriction were investigated. As the growth velocity increased, the solidification morphology transited from columnar to equiaxed. Simultaneously, the solid/liquid interface morphology evolved from planar to cellular, accompanied by an increase in the interface concave height. The ??001?? preferred orientation was detected along the axial direction of the grown rod at 10?mm/h. With the increased growth velocity, the ??001?? preferred orientation deviated from the axial direction, and the ??001?? orientation degree was weakened. The saturation magnetostriction of the grown rod was 305?ppm at 10?mm/h, but it deteriorated at higher velocities. The decreased magnetostriction was attributed to the microstructure transition and the weakened ??001?? preferred orientation.     

Physicochemical aspects of technology of the Al2O3-Al layered cermet obtained using reaction sintering

Certain features of the technology of the Al₂O₃-Al layered cermet obtained by the reaction sintering (RS) in air of powdered billets that were fabricated by pressing the charge from the PAP-2 plateletshaped aluminum powder. The RS process was activated by the introduction of a dry residue of liquid glass (DRLG) into the charge (C = 3?C28%). According to the data of the X-ray phase analysis, the sintered material contains (vol %): Al (61?C82), ??-Al₂O₃ (8?C25), Na₂Si₂O₅ (2?C15), and Si (1?C14). Oxide phases and silicon are nanodimensional morphological objects (13?C100 ??m) in the layered aluminum host. The cermet density is 2.1?C2.45 g/cm³, tensile strength is 45?C90 MPa, and the ultimate bending strength is 320 MPa. The activation of RS by a small DRGL additive (3%) retains the layered cermet structure. It is leveled at a considerable increase in the RS time (up to 600 min) or C (up to 28%) because of recrystallization and involves plateletshaped aluminum particles in the chemical interaction.     

Unique metallic glass formability and ultra-high tensile strength in AlNiFeGd alloys

The metallic glass formability of aluminum-rich AlNiFeGd alloys has been systematically investigated. The critical cooling rate required to form an amorphous state in this system is generally low, and comparable to that of some of the best metallic glass formers, such as PdCuSi. Amorphous ribbons up to 0.25 mm thick can easily be produced by the single-roller melt-spinning technique. Tensile strengths as high as 1280 MPa and Young's modulus of 75 GPa have been obtained. Bulk amorphous alloys with good mechanical properties are optimized in Al₈₅Ni₆Fe₃Gd₆. DSC and DTA studies reveal that the glass formability is unique for Al-based alloys because the reduced glass temperature T_rg for AlNiFeGd can be as low as 0.44. This is much lower than conventional theory would suggest for easy glass forming systems. A mechanism for the unusual glass formability is suggested.     

Structure and mechanical and corrosion properties of new high-nitrogen Cr-Mn steels containing molybdenum

The structure, mechanical properties, and pitting corrosion of nickel-free high-nitrogen (0.8% N) austenitic 06Kh18AG19M2 and 07Kh16AG13M3 steels have been studied in various structural states obtained after hot deformation, quenching, and tempering at 300 and 500°C. Both steels are shown to be resistant to the ?? ?? ?? and ?? ?? ? martensite transformations irrespective of the decomposition of a ?? solid solution (06Kh18AG19M2 steel). Austenite of the steel with 19 wt % Mn shows lower resistance to recrystallization, which provides its higher plasticity (??₅) and fracture toughness at a lower strength as compared to the steel with 13 wt % Mn. Electrochemical studies of the steels tempered at 300 and 500°C show that they are in a stable passive state during tests in a 3.5% NaCl solution and have high pitting resistance up to a potential E _pf = 1.3?C1.4 V, which is higher than that in 12Kh18N10T steel. In the quenched state, the passive state is instable but pitting formation potentials E _pf retain their values. In all steels under study, pitting is shown to form predominantly along the grain boundaries of nonrecrystallized austenite. The lowest pitting resistance is demonstrated by the structure with a double grain boundary network that results from incomplete recrystallization at 1100°C and from the existence of initial and recrystallized austenite in the 07Kh16AG13M3 steel. To obtain a set of high mechanical and corrosion properties under given rolling conditions (1200?C1150°C), annealing of the steels at temperatures no less than 1150°C (for 1 h) with water quenching and tempering at 500°C for 2 h are recommended.     

Improving the Mechanical Properties of Fe-Nb-(Ni-Mn) Dendrite-Ultrafine Eutectic Composites via Controlling the Primary Phase Features

Tuning of microstructure by addition of austenite stabilizers effectively enhances the mechanical properties in Fe-Nb-(Ni-Mn) dendrite-ultrafine eutectic composites. The Fe₉₃Nb₇ alloy displays the improved plasticity up to 10?pct due to the introduction of a ductile ??-Fe dendrite into the ultrafine eutectic matrix. Meanwhile, the Fe₇₈Nb₇Ni₁₀Mn₅ alloy, which forms an in-situ martensitic ????-Fe dendritic phase reinforced ultrafine eutectic composite exhibits excellent combination of a high fracture strength of 1.6?GPa and a large plastic strain of 11?pct. The investigations reveal that the characteristics of the modulated primary dendrites in the dendrite-ultrafine eutectic composites play an important role in manipulating the generation and propagation of shear bands, thus resulting in the improved mechanical properties and plastic deformation behavior.     

Microstructure Evolution and Analysis of A [011] Orientation, Single-Crystal, Nickel-Based Superalloy During Tensile Creep

By means of the elastic?Cplastic finite-element method (FEM) for calculating the distribution features of the von Mises stress and strain energy density, the influences of the applied stress on the von Mises stress of the ????/?? phases and the rafting of the ???? phase for the [011] orientation, single-crystal, nickel-based superalloy are investigated. The results show that, after being fully heat treated, the microstructure of the [011] orientation, single-crystal, nickel-based superalloy consists of the cuboidal ???? phase embedded coherently in the ?? matrix, and the cuboidal ???? phase on (100) plane is regularly arranged along a 45?deg angle relative to the [011] orientation. Compared with the matrix channel of [010] orientation, the bigger von Mises stress is produced within the [001] matrix channel when the tensile stress is applied along the [011] orientation. Under the action of the larger principal stress component, the bigger expanding lattice strain occurs on the (001) plane of the cuboidal ???? phase along the [010] direction, which may trap the Al, Ti atoms with a bigger atomic radius for promoting the directional growth of the ???? phase into the stripe-like rafted structure along the [001] orientation. The changes of the interatomic potential energy, misfit stress, and interfacial energy during the tensile creep are thought to be the driving forces of promoting the elements?? diffusion and directional growth of the ???? phase.     

过冷处理对Cu45Zr42Al8Ag5非晶热稳定性及力学性能的影响

采用过冷液体等温处理的方法制备出直径为3 mm的Cu45Zr42Al8Ag5合金圆棒,研究了过冷液体等温处理对铜基内生复合材料的热稳定性和力学性能的影响,研究表明,过冷处理后的试样均为原位自生晶体/非晶复合材料,且其有较好的热稳定性.由铜基非晶合金压缩后的应力--应变曲线可以看出,随保温时间的延长,最大抗压强度逐渐降低...     

Phase Equilibria Studies of the Cu-Fe-O-Si System in Equilibrium with Air and with Metallic Copper

Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373?K and 1673?K (1100?°C and 1400?°C) and (2) with metallic copper at temperatures between 1373?K and 1573?K (1100?°C and 1300?°C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of ??Cu₂O??-??Fe₂O₃??-SiO₂ ternary sections. The relationships between the activity of CuO_0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems.     

复合轧制SM45钢板的组织性能

 连铸坯直接轧制生产特厚钢板时,由于压缩比的限制,很难生产出厚度超过100 mm的高质量钢板。采用复合轧制工艺可生产出厚度为260 mm的SM45复合钢板。对钢板进行探伤、冷弯、拉伸、冲击及硬度等试验检验其结合度和力学性能。结果表明,复合轧制生产的SM45钢板结合度良好,未发现明显的缺陷存在。钢板复合界面与基体的强度均在600 MPa以上;[Z]向试样的强度也达到600 MPa以上,断面收缩率在30%以上;冲击功在37 J以上。钢板不同位置处的基本组织都为铁素体与珠光体,但晶粒尺寸不同。复合界面处的组织为一条铁素体为主的带状组织,该组织的产生是由先共析铁素体导致的。     

Correlation of Microstructure with Mechanical Properties of Zr-Based Amorphous Matrix Composite Reinforced with Tungsten Continuous Fibers and Ductile Dendrites

A Zr-based amorphous matrix composite reinforced with tungsten continuous fibers in an amorphous LM2 alloy matrix containing ductile ?? dendrites was fabricated without pores or defects by the liquid pressing process, and its tensile and compressive properties were examined in relation with microstructures and deformation mechanisms. Overall, 68?vol pct of tungsten fibers were distributed in the matrix, in which 35?vol pct of ?? dendrites were present. The LM2 composite had the greatly improved tensile strength and elastic modulus over the LM2 alloy, and it showed a stable crack propagation behavior as cracks stopped propagating at the longitudinal cracks of tungsten fibers or ductile ?? dendrites. According to the compressive test results, fracture did not take place at one time after the yield point, but it proceeded as the applied loads were sustained by fibers, thereby leading to the maximum strength of 2432?MPa and plastic strain of 16.4?pct. The LM2 composite had the higher strength, elastic modulus, and ductility under both tensile and compressive loading conditions than the tungsten-fiber-reinforced composite whose matrix did not contain ?? dendrites. These distinctively excellent properties indicated a synergy effect arising from the mixing of amorphous matrix and tungsten fibers, as well as from the excellent bonding of interfaces between them.     

Control over the particle size of stainless-steel powders

Conclusions Replacing some of the metallic iron by ferric oxide, Fe₂O₃, in the charge for the preparation of Kh18N15 and Kh23N28 stainless-steel powders by the calcium-hydride reduction process increases (two- to threefold) the yield of the fine fraction (-0.063 mm) without affecting the apparent density of the powders (1.4–1.85 g/cm³) or the sponge shape of their particles. At the present time, stainless-steel powders are being manufactured using a charge in which 20–30% of metallic iron has been replaced by the oxide Fe₂O₃.Translated from Poroshkovaya Metallurgiya, No. 2 (134), pp. 1–8, February, 1974.     

Formation and Thermal Stability of Cu-Based Metallic Glasses with High Glass-Forming Ability

Cu-based Cu-Zr-Al metallic glass samples with diameters of more than 10?mm could be produced in a composition range of 45 to 52 (at. pct) Cu, 41 to 47?at.?pct Zr, and 6 to 10?at.?pct Al by a copper mold casting method. The best glass-forming ability was obtained for the Cu₄₇Zr₄₅Al₈ alloy, and the glassy sample with a diameter of 15?mm was fabricated. The minor addition of Ag or Dy can enhance the glass-forming ability of the Cu₄₇Zr₄₅Al₈ alloy, which decreases the liquidus temperatures, leading to increase in the reduced glass transition temperature. Fully glassy samples with diameters up to 20?mm were obtained for a (Cu_0.47Zr_0.45Al_0.08)₉₈Dy₂ alloy.     

Thermodynamic Basis for Glass Formation in Cu-Zr Rich Ternary Systems and Their Synthesis by Mechanical Alloying

Topological factors such as mismatch entropy and configurational entropy, along with thermodynamic entity such as enthalpy of chemical mixing, are found to control glass formation in metallic systems. Taking both these factors into consideration, a parameter called P _HS was proposed to correlate glass forming ability successfully in the Cu-Zr-Ti system. The parameter P _HS (=?H _chem × ?S _σ /k _B ) is a product of enthalpy of chemical mixing and mismatch entropy. Our study indicates that the more negative is the P_HS value within the configurational entropy (?S _config/R) range of 0.9 to 1.0, the higher is the stability of glassy phase resulting in a larger diameter of bulk metallic glass rods. Observed theoretical predictions are supported by experimental results in which the compositions with high negative P _HS resulted in easy amorphous phase formation in comparison with less negative P _HS compositions by mechanical alloying. This criterion was extended to Cu-Zr-Al and Cu-Zr-Ag systems as well, thus establishing a strong correlation between P _HS and the glass forming ability of alloys. The role of size effect, probability of atomic arrangements, and heat of formation among constituent elements in obtaining a larger dimension bulk metallic glasses was addressed in this study.     

Tunable Curie temperature and magnetocaloric effect of FeCrMoCBYNi bulk metallic glass with different crystallized phases

The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that the Curie temperature(T_c) of Fe_(45)Cr_(15)Mo_(14)C_(15)B_6 Y_2 Ni_3 BMG with different annealing condition reaches a highest value of 95 K. The value of magnetic entropy change △S_M(T) of Sample 3 reaches a maxima of 0.48 J/(kg·K) at Tc temperature, which result from the interaction among the precipitated phases of(Fe,Cr)_(23)(C,B)_6, Fe_3 Mo_3 C and residual amorphous phase. Based on the experiment results, it can be obtained that the Curie temperature, magnetocaloric effect can reach their optimal value at low temperature, when the content of amorphous phase and precipitated phases type run up to certain value. The magnetic properties of Sample 1 with full amorphous phase and Sample 4 with full crystalline phase will both decrease.     

Mechanical properties of Fe-Si-B amorphous wires produced by in-rotating-water spinning method

Amorphous wires with high strength and good ductility have been produced in Fe-Si-B alloy system by the modified melt-spinning technique in which a melt stream is ejected into a rotating water layer. These wires have a circular cross section and smooth peripheral surface. The diameter is in the range of about 0.07 to 0.27 mm. Their Vickers hardness (H_v) and tensile strength (σ_f) increase with silicon and boron content and reach 1100 DPN and 3920 MPa, respectively, for Fe₇₀Si₁₀B₂₀, exceeding the values of heavily cold-drawn steel wires. Fracture elongation(ε _f ), including elastic elongation, is about 2.1 to 2.8 pct. An appropriate cold drawing results in the increase of σ_f and ε_f by about eight and 65 pct, respectively. This increase is interpreted to result from an interaction among crossing deformation bands introduced by cold drawing. The undrawn and drawn amorphous wires are so ductile that no cracks are observed, even after closely contacted bending. Further, it is demonstrated that the σ_f of the Fe₇₅Si₁₀B_l5 amorphous wire increases by the replacement of iron with a small amount of tantalum, niobium, tungsten, molybdenum, or chromium without detriment to the formation tendency of an amorphous wire. Such iron-based amorphous wires are attractive as fine gauge, high strength materials because of their uniform shape and superior mechanical qualities.     

A Novel Metastable Ti-25Nb-2Mo-4Sn Alloy with High Strength and Low Young’s Modulus

A novel metastable ?? Ti-25Nb-2Mo-4Sn (wt pct) alloy with high strength (1113?MPa) and low Young??s modulus (65?GPa) was prepared. Nanometer-scaled ?? precipitates as well as the dislocations play a key role in strengthening. The ?? phase containing low content of ??-stabilizers is stabilized with the assistance of thermomechanical treatment, resulting in a relatively low elastic modulus. Therefore, the current alloy performs high strength-to-modulus ratio and could be a potential candidate for biomedical applications.     

Effects of Dendrite Size on Tensile Deformation Behavior in Zr-Based Amorphous Matrix Composites Containing Ductile Dendrites

Four Zr-based amorphous matrix composites whose dendrite size was varied with plate thickness were investigated, and the deformation mechanisms related with improvement of strength and ductility were investigated by focusing on how the size of ductile ?? dendrites affected the initiation and propagation of deformation bands. These composites contained 47 to 49?vol pct of dendrites sized by 14.7 to 42.8???m, and they showed excellent tensile properties of yield strength of 1.3 to 1.5?GPa and uniform elongation up to 11.7?pct. According to the observation of tensile deformation behavior of the composite with a plate thickness of 5?mm, many deformation bands were formed inside dendrites in several directions, and the deformation bands met crossly each other to form widely deformed areas. Because the wide and homogeneous deformation in this composite beneficially worked for the tensile strength and ductility simultaneously, the optimum size of dendrites and thickness of plates were approximately 19???m and 5?mm, respectively. Considering that Zr-based amorphous matrix composites are mostly used in a plate form in their conventional applications, the current research can provide the optimum plate thickness data for their fabrication processes such as rolling, extrusion, and strip casting.     

Refinement of Ferrite Grain Size near the Ultrafine Range by Multipass, Thermomechanical Compression

Plane-strain compression testing was carried out on a Nb-Ti-V microalloyed steel, in a GLEEBLE3500 simulator using a different amount of roughing, intermediate, and finishing deformation over the temperature range of 1373?K to 1073?K (1100?°C to 800?°C). A decrease in soaking temperature from 1473?K to 1273?K (1200?°C to 1000?°C) offered marginal refinement in the ferrite (??) grain size from 7.8 to 6.6???m. Heavy deformation using multiple passes between A _e3 and A _r3 with true strain of 0.8 to 1.2 effectively refined the ?? grain size (4.1 to 3.2???m) close to the ultrafine size by dynamic-strain-induced austenite (??) ?? ferrite (??) transformation (DSIT). The intensities of microstructural banding, pearlite fraction in the microstructure (13?pct), and fraction of the harmful ??cube?? texture component (5?pct) were reduced with the increase in finishing deformation. Simultaneously, the fractions of high-angle (>15?deg misorientation) boundaries (75 to 80?pct), beneficial gamma-fiber (ND//??111??) texture components, along with {332}??133?? and {554}??225?? components were increased. Grain refinement and the formation of small Fe₃C particles (50- to 600-nm size) increased the hardness of the deformed samples (184 to 192?HV). For the same deformation temperature [1103?K (830?°C)], the difference in ??-grain sizes obtained after single-pass (2.7???m) and multipass compression (3.2???m) can be explained in view of the static- and dynamic-strain-induced ?? ?? ?? transformation, strain partitioning between ?? and ??, dynamic recovery and dynamic recrystallization of the deformed ??, and ??-grain growth during interpass intervals.     

Effects of Changes in Chemistry on Flex Bending Fatigue Behavior of Al-Based Amorphous Alloy Ribbons

The effects of changes in composition on the flow behavior and flex bending fatigue behavior of a series of Al-Gd-Ni-X (X?=?Fe or Co) amorphous alloy ribbons have been determined at 1?Hz at room temperature. It has been shown that the addition of Fe, Co, and Fe/Co combination into these materials increases the strength, T _g, and T _x1 in addition to the activation energy for crystallization. The lowest strength (i.e., 880?MPa) base alloy Al₈₇Gd₆Ni₇ exhibited the best low-cycle fatigue (LCF) and worst high-cycle fatigue (HCF) behavior, whereas the higher strength alloys (~1100?MPa) Al₈₅Gd₆Ni₇Fe₂ and Al₈₅Gd₆Ni₇Fe₁Co₁ exhibited worse LCF and better HCF behavior. The ratio of the stress amplitude at the fatigue limit at 1?×?10⁶ cycles to uniaxial failure strength ranged from 0.25 to 0.37 (240 to 397?MPa), much higher than conventional aluminum alloys. These results are also compared with those obtained on other amorphous alloy ribbons.     

Crystallization of Phase-Separated Pd41.25Ni41.25P17.5 BMGs

Phase-separated Pd_41.25Ni_41.25P_17.5 bulk metallic glasses (BMGs) were subjected to isothermal annealing at 613 K (340 °C) for different time periods, t, in the range of 0 ≤ t ≤ 8 hours. For 0 ≤ t ? 5 hours, crystalline precipitates, in the shape of spheres, appear and its density is more or less a linear function of t. They are randomly distributed in the amorphous matrix. For t ? 5 to 6 hours, the number density of the spherical crystalline precipitates increases rapidly. In addition, they are no longer distributed randomly in the phase-separated amorphous matrix. Clustering is displayed. Experimental results suggest that the clustering is due to cubic crystalline precipitates that start to appear when t ≈ 5 to 6 hours.