Effect of Laser Surface Modification on the Structure and Mechanical Properties of Al–8% Ca,Al–10% La,Al–10% Ce,and Al–6% Ni Eutectic Aluminum Alloys

Russian Journal of Non-Ferrous Metals - Additive manufacturing, which includes a set of technologies for manufacturing complex-shaped products with the required set of properties, is currently...     

Microstructure,tensile deformation,and fracture in aged ti 10V-2Fe-3Al

In the /3-Ti alloy Ti-10V-2Fe-3Al a variety ofα-andω-aged microstructures with different yield stresses was established by combinations of forging and heat treatment. Tensile tests have shown that plastic deformation and fracture are strongly influenced by the morphology, size, and volume fraction of the different types of a-phase (primary a, secondaryα, grain boundaryα), as well as by the-phase. A detailed microscopical study revealed several deformation and fracture modes. It appears that at several sites stress and strain concentrations and subsequent void nucleation can occur and that the quantitative combinations of the differentα-types determine which sites are active. The dominant deformation mode for the (α +gb) solution treated andα-aged conditions was a strain localization in theα-aged matrix leading to voids at the interface between aged matrix and primary a-phase. In case of theβ-solution treated andα-aged microstructures the grain boundaryα leads to a strain localization in the softα-film and to void nucleation at grain boundary triple points at low macroscopic strains. Based on the above mechanisms it is discussed in detail how varying size, volume fraction, and morphology of theα-phase affect the ductility. The embrittling effect ofω-particles can be largely reduced by a grain refinement.     

Crystallisation process of Al80Fe10Ti10 amorphous phase

Abstract

In the present study, crystallisation behaviours of the Al₈₀Fe₁₀Ti₁₀ amorphous phase (prepared by mechanical alloying) has been investigated using X-ray diffraction and differential thermal analysis techniques. It was found that Al₈₀Fe₁₀Ti₁₀ amorphous phase exhibits one-stage crystallisation on heating [amorphous to Al₁₃Fe₄, Al(Fe,Ti) and Al₅Fe₂ intermetallic phases]. The activation energies for crystallisation of Al₈₀Fe₁₀Ti₁₀ amorphous phase were determined as 326, 322, 351 and 301 kJ mol^?1 by means of the Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa, Friedman and Afify equations respectively. Kinetic parameters such as Avarmi exponent or reaction order n and frequency factor K_o were also discussed. The reaction orders obtained for the crystallisation was ～2·03, suggesting that a diffusion controlled crystallisation process with a decreasing nucleation rate was the crystallisation mechanism. The deduced K_o value for crystallisation peak was calculated to be 6·75×10¹⁰ s^?1.     

Structural Relaxation of La55Al25Ni10Cu10 Bulk Metallic Glass

The relaxation process and glass transition kinetics of the La₅₅Al₂₅Ni₁₀Cu₁₀ bulk metallic glass (BMG) below the calorimetric glass transition were investigated by differential scanning calorimetry. Enthalpy relaxation was observed in isothermal annealing experiments below the glass transition temperature T _g . The time-dependent enthalpy relaxations were well described by a stretched exponential relaxation function, with an exponential index 0.78. An apparent activation energy E = 60.8 kJ/mol was derived from the temperature dependence of the relaxation time. The equilibrium free volume concentration at a temperature about 30 K below T _g is 10⁻¹⁷ to 10⁻¹³, calculated using an empirical Vogel–Fulcher–Tammann (VFT) type equation. This article is based on a presentation given in the symposium entitled “Bulk Metallic Glasses IV,” which occurred February 25–March 1, 2007 during the TMS Annual Meeting in Orlando, Florida under the auspices of the TMS/ASM Mechanical Behavior of Materials Committee.     

The Effects of Fatigue on the Atomic Structure with Cyclic Loading in Zr50Cu40Al10 and Zr60Cu30Al10 Glasses

The potential damage effect from fatigue on Zr bulk metallic glass alloys of Zr₅₀Cu₄₀Al₁₀ at the eutectic point and Zr₆₀Cu₃₀Al₁₀ away from the eutectic point (in atomic percent) is examined via the local atomic structure, which was obtained from the pair density function analysis of the synchrotron X-ray radiation and neutron data. Samples cut from the same rods were subjected to 10⁴, 10⁵, and 10⁶ compression cycles ex situ, and the evidence for fatigue damage was investigated by comparing alloys before and after cyclic loading. Bond orientation was observed particularly in Zr₅₀Cu₄₀Al₁₀, suggesting that fatigue damage occurs even in the elastic range, below the yield point, and during cyclic loading. The initiation of fatigue changes is observed first within small localized atomic regions.     

Quantitative evaluation of inclusion in deoxidation of Fe-10 mass pct Ni alloy with Si, Ti, Al, Zr, and Ce

The composition, size, number, and morphology of the inclusions in deoxidation of Fe-10 mass pct Ni alloys with 0.2 mass pct M (M=Si, Ti, Al, Zr, and Ce) containing mostly 60 to 130 mass ppm oxygen were studied as a function of holding time at 1873 K. It was found that the initial primary inclusions contained FeO and the FeO content decreased with an increase of deoxidation power and holding time. The mean spatial diameter of inclusions tends to increase with increasing holding time, but did not show the systematic trend with respect to the deoxidation power. The number of particle sections per unit area decreased with decreasing deoxidation power and increasing holding time. In the absence of stirring of melt, the growth rate of the mean spatial diameter of inclusions and the removal rate of particle sections per unit area decreased rapidly with increasing holding time and approached a constant after 10 minutes. The morphology of inclusions was found to be spherical, polyhedral (except Si), and irregular including cluster, and the mean spatial diameter of these inclusions increased with increasing holding time.     

Processing properties relationships of Ti-10V-2Fe-3Al

Beta alloys, such as Ti-10V-2Fe-3Al, can be processed and heat treated to provide a wide range in mechanical and fracture properties. A systematic study of the effect of processing and heat treatment variations on the properties combinations achievable was undertaken. The ductility and fracture toughness can be very significantly influenced by processing and heat treatment variations. The ductility increases and the toughness decreases as the morphology of the primary alpha changes from acicular to equiaxed. This morphology change was caused by alterations in forging procedures. Reducing the strength increases both fracture toughness and ductility. Microstructure has only a minor influence on fatigue performance in the high strength (about 1310 MPa UTS) condition. The micro-structure does, however, have a significant effect on fatigue behavior in a low strength, about 1034 MPa UTS, condition. More lamellar alpha results in improved notched fatigue performance, while a more equiaxed alpha improves smooth fatigue performance. These changes in properties are rationalized in terms of microstructure.     

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.     

Synthesis and characterization of Al foam, Al alloy foam and Al-SiC composite foam

Open-celled Al foam, Al-Mg alloy foam and Al-SiC composite foams were prepared by means of sintering and dissolution process. The microstructures and compressive behaviour of these foams were studied. It was found that at the same relative density, the compressive strength increases with the addition of alloying element and silicon carbide. Energy absorption capacity curves show that the energy absorption capacity increases with the increase in strain.     

Deformation-Induced Grain Refinement and Amorphization in Ti-10V-2Fe-3Al Alloy

The microstructural evolution and grain refinement mechanisms of a Ti-10V-2Fe-3Al alloy, β-solution quenched and cold forged (CF) to strains of 0.1, 0.35, and 1.2 have been investigated using optical microscopy (OM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results showed that the stress-induced martensitic transformation became a predominant deformation mode in the metastable Ti-10V-2Fe-3Al alloy during cold forging. These martensites α″ repeatedly divided the original β parent phase into a large number of micron-sized blocks when the forging strain was 0.1. Shear bands were observed to traverse α″/β lamellae and resulted in a significant grain refinement of the β phase, as the forging strain increased to 0.35. The degree of grain refinement inside shear bands was higher than the outside. Nanocrystalline and amorphous structures were produced in local areas of the original β phase, when the forging strain rose to 1.2. This dramatic grain refinement in the metastable Ti-10V-2Fe-3Al alloy could be attributed to the stress-induced martensitic transformation promoting the initiation and growth of shear bands across α″/β lamellae. More dislocations were produced and accumulated inside grains to accommodate plastic deformation. The crystal structure was collapsed and an amorphous structure was formed as soon as the dislocation density was accumulated to a critical value of 10¹⁴/cm². Moreover, some of the reverse martensitic phase transformation, α″→β, was observed to contribute to grain refinement of Ti-10V-2Fe-3Al alloy as well.     

Zr_(55)Al_(10)Ni_5Cu_(30)非晶态合金的制备与性能研究

采用石墨坩埚浇铸法在真空中频感应熔炼炉中制备Zr55Al10Ni5Cu30合金,并对合金进行了金相、X射线衍射和显微硬度的测试,考察原料纯度、过热度及冷却速率对非晶态合金性能的影响。结果表明,采用工业级原料就可以制备出性能良好的非晶态合金,在低的冷却速率下形成的非晶态合金具有相对较高的硬度,适当提高过热度可以减少微晶的形成。     

Eu2+在BaM(M=Zn,Li,Mg)Al10O17基质中的发光性能

用燃烧法制备了掺杂不同离子的β-Al2O3结构基质,并探讨了Eu2+在此基质中的发光。Eu2+在Zn-β-Al2O3基质中的发射光谱发生蓝移,在一定程度上解决了绿色拖尾问题。