Microhardness of amorphous metallic alloys Fe-Cr-B

Translated from Poroshkovaya Metallurgiya, No. 8(332), pp. 49–53, August, 1990.     

Hydrogen effects on an amorphous Fe-Si-B alloy

Hydrogen absorption in and desorption from an amorphous Fe₈₀B₁₁Si₉ alloy, hydrogen effects on the microstructure of this alloy, and the possible mechanism of hydrogen embrittlement (HE) in this alloy have been studied. Ribbons were electrochemically charged with hydrogen at room temperature. The interaction of hydrogen with structural defects and the characteristics of hydrogen desorption were studied by means of thermal desorption spectroscopy (TDS). The effects of hydrogen on the microstructure and thermal stability were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), electrical resistivity measurements, and differential scanning calorimetry (DSC). The phenomenon of HE was investigated using scanning electron microscopy (SEM) and various mechanical testing techniques. The absence of hydride-forming elements resulted in low hydrogen solubility and low desorption temperatures. Hydrogenation at room temperature is reported for the first time to lead to either local nanocrystallization of the amorphous phase or transformation of nanocrystalline phases such as Fe_∼3.5B, originally present in the uncharged material, to a new nanocrystalline Fe₂₃B₆ phase. The susceptibility of this alloy to HE is explained in terms of high-pressure bubble formation.     

Y基非晶合金的形成及晶化动力学

利用单辊急冷法制备Y56-xZrxA124Co20(x=0,5,10)非晶合金,研究Zr含量对该非晶合金的形成能力及热稳定性的影响.研究结果表明,添加元素Zr可以提高Y56A124Co20合金的非晶形成能力和热稳定性,而且随着Zr含量增加,合金的非晶形成能力提高.通过示差扫描量热法(DSC)研究了Y56A124Co20和Y46Zr10A124Co20的晶化动力学,前者的玻璃转变激活能和晶化激活能分别为366.5 KJ/mol和259.7 KJ/mol,后者的玻璃转变激活能和晶化激活能分别为415.6 KJ/mol和319.5KJ/mol,从理论上说明添加元素Zr可以改善Y56A124Co20合金的非晶形成能力和热稳定性.     

Corrosion behavior of amorphous fe-cr-al-p-c ribbon alloys

Corrosion resistance of amorphous Fe₇₂Cr_8-xAl_xP₁₃C₇ ribbons produced by a rapid quenching method has been investigated in several solutions. The corrosion test for amorphous ribbons was carried out, and anodic polarization curves have been measured in the solutions. Resultantly, even in the amorphous Fe₇₂Cr_8-xAl_xP₁₃C₇ ribbons containing a low Cr content, this composition of amorphous alloys showed the high corrosion resistance.     

Effect of nanocrystallization on the mechanical behavior of Fe-Ni-based amorphous alloys

Melt-quenched amorphous alloys Fe₅₈Ni₂₅B₁₇, Fe₅₀Ni₃₃B₁₇, and Ni₄₄Fe₂₉Co₁₅B₁₀Si₂ are used to study the effect of the structural parameters of the nanocrystalline phases precipitating at the first stage of crystallization on the strength characteristics of the alloys in an amorphous-nanocrystalline state. It is shown that, at a constant nanoparticle size, the dependence of microhardness H _V on the volume fraction (V _V ) or the volume density (N _V ) of these nanoparticles can be described by the relation HV = K(V _V ) ⁿ , where n = 1/3. A relation HV = f(d) that is analogous to the Hall-Petch relation is detected at a fixed volume density of nanoparticles and their average size d > 80–100 nm. At d < 70–80 nm, HV decreases anomalously with decreasing d.     

Effect of the structure of amorphous electrodeposited Ni-W and Ni-Co-W alloys on their crystallization

The microstructure and phase composition of amorphous electrodeposited Ni-W and Ni-Co-W films are studied using transmission electron microscopy, X-ray diffraction, and differential thermal analysis. The thermal stability of the amorphous films is shown to depend on their chemical composition and network microstructure. The temperatures of the onset of crystallization and the sequence of phase transformations during transition to an equilibrium crystalline state are determined.     

Effect of yttrium on thermal stability and crystallization behavior of Nd60Fe20Al10Ni10 amorphous alloys

The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.     

Symmetry aspects of pretransformation behavior in metallic alloys

This paper deals with pretransformation behavior in both mineral and alloy systems. Theory that has previously been developed on the existence of local structural variants in incommensurate structures is reviewed and later applied to the study of local interactions in pretransformation phenomena. A review of the pretransformation behavior in both potassium feldspar and the mineral cordierite shows that the important feature in both cases is a very strong interaction between two orthogonal transverse acoustical waves to create a local shear structure. In the case of potassium feldspar this shear structure is the required product in the transformation, but in cordierite the first shear structure to appear in the pretransformation mechanism is not the correct one. Why this should be is explained in detail from a group theoretical analysis of the situation. Ultimately in cordierite this initial structure gives way to the correct structure with the appearance of twinning. The theory developed from the study of the mineralogical examples is then applied to the familiar cubic to tetragonal martensitic transformation in alloys such as In Tl with satisfactory results. Formerly with Schlumberger Cambridge Research, P.O. Box 153, Cambridge CB2 OHG This paper is based on a presentation made in the symposium “Pre-transformation Behavior Related to Displacive Transformations in Alloys≓ presented at the 1986 annual AIME meeting in New Orleans, March 2-6, 1986, under the auspices of the ASM-MSD Structures Committee.     

Bulk amorphous metallic alloys: Synthesis by fluxing techniques and properties

Bulk amorphous alloys having dimensions of at least 1 cm in diameter have been prepared in the Pd-Ni-P, Pd-Cu-P, Pd-Cu-Ni-P, and Pd-Ni-Fe-P systems using a fluxing and water-quenching technique. The compositions for bulk glass formation have been determined in these systems. For these bulk metallic glasses, the difference between the crystallization temperature (T _x) and the glass transition temperature (T _g, ΔT=T _x−T _g) ranges from 60 to 110 K. These large values of ΔT open the possibility for the fabrication of amorphous near-net-shaped components using techniques such as injection molding. The thermal, elastic, and magnetic properties of these alloys have been studied, and we have found that bulk amorphous Pd₄₀Ni_22.5Fe_17.5P₂₀ has spin glass behavior for temperatures below 30 K. This article is based on a presentation made in the “Structure and Properties of Bulk Amorphous Alloys” Symposium as part of the 1997 Annual Meeting of TMS at Orlando, Florida, February 10–11, 1997, under the auspices of the TMS-EMPMD/SMD Alloy Phases and MDMD Solidification Committees, the ASM-MSD Thermodynamics and Phase Equilibria, and Atomic Transport Committees, and sponsorship by the Lawrence Livermore National Laboratory and the Los Alamos National Laboratory.     

Ball-milling-induced crystallization and ball-milling effect on thermal crystallization kinetics in an amorphous FeMoSiB alloy

Microstructure evolution in a melt-spun amorphous Fe_77.2Mo_0.8Si₉B₁₃ alloy subjected to high-energy ball milling was investigated by means of X-ray diffraction (XRD), a transmission electron microscope (TEM), and a differential scanning calorimeter (DSC). It was found that during ball milling, crystallization occurs in the amorphous ribbon sample with precipitation of an α-Fe solid solution, and the amorphous sample crystallizes completely into a single α-Fe nanostructure (rather than α-Fe and borides as in the usual thermal crystallization products) when the milling time exceeds 135 hours. The volume fraction of material crystallized was found to be approximately proportional to the milling time. The fully crystallized sample with a single α-Fe nanophase exhibits an intrinsic thermal stability against phase separation upon annealing at high temperatures. The ball-milling effect on the subsequent thermal crystallization of the amorphous phase in an as-milled sample was studied by comparison of the crystallization products and kinetic parameters between the as-quenched amorphous sample and the as-milled partially crystallized samples. The crystallization temperatures and activation energies for the crystallization processes of the residual amorphous phase were considerably decreased due to ball milling, indicating that ball milling has a significant effect on the depression of thermal stability of the residual amorphous phase.     

电脉冲退火处理对Fe-Si-B非晶原子结合力的影响

非晶态合金Fe78Si9B1 3样品经短时超短脉冲电流处理 ,发生了结构弛豫 ,用DTA方法及Kissinger方程计算非晶样品的晶化激活能 ,用穆斯堡尔谱学方法研究了试样在电脉冲处理后的无反冲分数的变化 .结果表明 ,随脉冲电流密度和脉冲频率的增加 ,样品的晶化激活能降低 ,穆斯堡尔无反冲分数下降 ,表明原子间结合力随电流密度和脉冲频率的增加趋向降低     

The effect of minor alloying elements on the mechanical properties of Al-Cu-Li alloys

The monotonic and cyclic properties of two Al-Cu-Li alloys were investigated. The alloys were similar in composition to aluminum alloy 2020 but had a higher purity and a different ancillary addition. Property-microstructure comparisons are made between the various materials. The modified alloys have a 40 pct higher fracture toughness than TMT 2020 and overall monotonie properties comparable with 7075-T651. In addition, they have a 17 pct higher specific modulus than current high strength aluminum alloys. Formerly a Visiting Scholar at the Lockheed-Georgia Company, Marietta, GA     

Theoretical analysis of the conditions required for rendering metallic alloys amorphous during gas-thermal spraying

Translated from Poroshkovaya Metallurgiya, No. 9(357), pp. 56–61, Septemebr, 1992.     

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.