Mechanical Alloying Duration Research Articles

Microstructure, thermal and radiation shielding properties of aluminium‐silicon‐boron alloy prepared by mechanical alloying

AbstractThis study focused on developing microstructural, thermal, and radiation shielding changes in Al50Si25B25 powders using mechanical alloying techniques. Based on the x‐ray powder diffraction data, the crystallite size and microstrain of the 100‐hours milled powder were calculated as 0.25 nm and 50.33 %, respectively. The solubility of silicon in the α‐aluminium matrix increased with longer mechanical alloying duration. Transmission electron microscope analyses further showed that the alloy particulates had an average size of 3 μm and an average grain size of 0.226 nm. The radiation shielding properties of the Al50Si25B25 powders indicated that the Linear Attenuation Coefficient value increased from 0.0554±0.1689 cm−1 to 1.0632±0.2425 cm−1 with an increase in the thickness of the Al50Si25B25 alloy. This work successfully demonstrated the potential of mechanical alloying techniques to enhance the microstructural and thermal properties of Al50Si25B25 powders. It highlighted their effectiveness in providing radiation shielding capabilities when varying the thickness of the alloy.

Few-layered graphene/Al-Cu alloy matrix composites: Mechanical, tribological and corrosion properties

Nano-sized graphene incorporated Al-5.5 wt% Cu alloy matrix composites were produced via powder metallurgy. Nano-sized graphene powders obtained via the arc-discharge method were incorporated into Al and Cu powders in varying amounts (0–5 wt%) by applying a high-energy ball milling (HEBM) process for different durations. The consolidated composites were prepared by the succeeding uni-axial pre-compaction and pressureless sintering stages. The as-blended and mechanically alloyed (MAed) powders and bulk composites were comparatively characterized in terms of their physical, thermal, microstructural, tribological, mechanical, and corrosion properties depending on the graphene amount and the duration of mechanical alloying (MA). After 4 h of MA, the starting as-blended powders presented as coarse and discrete particles gained a refined and homogenized microstructure with more equiaxed dimensions. Bulk FLG/Al-5.5Cu (FLG in amounts of 0, 0.5, 1, 2, and 5 wt%) composites are ever-increasing hardness values with rising graphene as 109, 101, 128, 238, and 263 HV, respectively. The compressive strength improved gradually to 495 MPa using graphene up to 1 wt%, though contrary to the high hardness values, a drastic decline was observed by 5 wt% graphene incorporation. Besides, the wear resistance of composites outperformed that of the Al-5.5Cu matrix by incorporating this amount of reinforcement together without a deterioration in the corrosion resistance.

Microstructure-property evolution of mechanically alloyed Al-20 wt% Si matrix powders and sintered composites reinforced withTiB2 particulates

Microstructural, physical and mechanical properties of Al–20 wt% Si matrix alloy powders and those reinforced with TiB2 and their sintered composites were investigated in relation to TiB2 content and mechanical alloying (MA) durations. Al–20 wt% Si matrix alloy powders and those containing 5 and 10 wt% TiB2 reinforcing particles were MA’d for 1, 2, 4, and 8 h followed by consolidation and sintering at 843 K. Si solubility in a-Al matrix increased with increasing MA duration. Increasing the TiB2 content, on the other hand, resulted in a systematic drop in Si solubility over the same MA period. Scanning electron micrographs of the sintered samples revealed sub-micron-sized, rod-shaped Si and spherical Al9Si phase particles. With increasing TiB2 content and MA durations, the microhardness of the Al20Si/TiB2 composites improved. The wear resistances of TiB2 reinforced composites better by 5 to 8 times than that of the as-blended and 1 h MA’d AlSi matrix alloy. Due to the presence of the Al3Ti intermetallic phase, sintered composite samples containing 10 wt% TiB2 particles MA'd for 8 h had the maximum hardness value and lower wear resistance values than those of the Al–20 wt% Si/5 wt% TiB2 composites.

Effect of Mechanical Alloying on Structural and Electrical Properties of (P<sub>2</sub>O<sub>5</sub>)<sub>(x)</sub>-(Y<sub>2</sub>O<sub>3</sub>)<sub>(0.03)</sub>-(ZrO<sub>2</sub>)<sub>(0.97)</sub> Electrolyte

Pentavalent phosphorous oxide doped yttria-stabilized zirconia (P2O5)X-(Y2O3)0.03-(ZrO2)0.97 with x=0.06 mol.% was achieved via an economical technique using mechanical alloying (MA) technique. Three types of nanocomposite powders of electrolyte were produced by high-energy ball milling with different milling times. The phases of synthesized electrolyte powders and sintered electrolytes were illustrated by X-ray diffraction (XRD). The average particle sizes of powders indicated around (360, 245, and 48) nm at milling duration (1, 10, and 45) hrs, respectively. The XRD analysis results of 1 h MA electrolyte powder obtained tetragonal ZrO2, while the 45 h MA electrolyte manifested a minority phase of monoclinic ZrO2. Then, the XRD of the sintered electrolyte with the optimum electrical properties appeared two phases. The major phase of the tetragonal zirconium yttrium oxide and a minor phase was a monoclinic zirconium oxide. The average grain sizes of the three types of the sintered manufacturing electrolytes were (7.638, 2.642, and 1.245 µm) after the mechanical alloying duration of (1, 10, and 45) hrs, respectively and sintered at 1873 °K. The DC conductivity (σ) studied corresponded to the influence of milling times on the microstructure for each sintered electrolyte. From the results, the synthesized sintered electrolyte with a long MA duration gave a maximum DC (σ) 1.03E-1S.m. And, the DC conductivity (σ) was 1.11E-02 of electrolyte produced with 10 hr mechanical alloying. Otherwise, the lower DC conductivity got with the electrolyte prepared in the lowest milling duration was 8.9 E-2 S.m.

High thermoelectric performance of p-type half-Heusler (Hf,Ti)Co(Sb,Sn) solid solutions fabricated by mechanical alloying

Mechanical alloying synthesis was applied on the thermoelectric half-Heusler materials in order to explore the potential of such scalable synthesis method in this family of compounds. (Hf,Ti)Co(Sb,Sn) solid solutions were prepared by mechanical alloying followed by hot pressing and their thermoelectric properties were studied in the temperature range of 300–980 K. After successful synthesis, two different methods were applied to enhance the thermoelectric performance of p-type (Hf,Ti)Co(Sb,Sn) materials: (a) adjustment of the Ti/Hf ratio and (b) fine tuning of carrier concentration by the substitution of Sb with Sn. The isoelectronic substitution of Ti with Hf led to an important reduction in the lattice thermal conductivity and a high ZT of 0.84 at 980 K for Hf0.6Ti0.4CoSb0.8Sn0.2. The effect of charge carrier concentration was investigated by preparing Hf0.6Ti0.4CoSb1−ySny (0.15, 0.17, 0.20, 0.23, 0.25) compounds, using different mechanical alloying durations. The Hf0.6Ti0.4CoSb0.83Sn0.17 composition, prepared by 4 h ball-milling, reached an impressive ZT ~1.1 at 973 K.

Characterization of LaB6 particulate-reinforced eutectic Al-12.6 wt% Si composites fabricated via mechanical alloying and spark plasma sintering

In this study, x wt% LaB6 (x = 0, 2, 5 and 10) particulate-reinforced eutectic Al-12.6 wt% Si powders and composites were prepared from commercial Al, Si and LaB6 starting materials via powder metallurgy methods. Mechanical alloying (MA) was conducted on the blended powders using a high-energy ball mill (at 1060 cycles/min) for 2, 4 and 8 h. Mechanically alloyed (MA'd) powders were subjected to cold pressing (CP, under 450 MPa) and spark plasma sintering (at 450 °C for 180 s) processes. Powder particle morphologies changed from flaky to semi-equiaxial shape after MA duration of 4 h. Calculations performed through the XRD patterns of Al phase revealed that the average crystallite size increased and the average lattice strain decreased with increasing MA duration and LaB6 content. Spark plasma sintered (SPS'd) samples were examined in terms of composition, microstructure, densification and mechanical properties (hardness, yield strength, compressive strength and wear volume loss). Studies revealed that 4 h was the optimal MA duration and 10 wt% was the optimal reinforcement content for the LaB6particulate-reinforcedAl-12.6 wt% Si composites with respect to their mechanical properties. Al-12.6 wt% Si-10 wt% LaB6 sample had the highest hardness (1.72 ± 0.12 GPa), yield strength (373 MPa), compressive strength (578 MPa) and lowest wear rate (0.001 mm3/Nm) values among all SPS'd samples.

Characterization investigations of the mechanically alloyed and sequentially milled Al-12.6 wt.% Si eutectic alloy powders

This study reports on the detailed microstructural characterization of Al-12.6 wt.% Si eutectic alloy powders synthesized from Al and Si elemental starting materials via mechanical alloying (MA) for 4, 6, and 8 h, and subsequent cryomilling (CM). Mechanically alloyed (MA’d) powders were cryomilled (CM’d) for 10, 20, and 30 min in a freezer/mill using liquid N2 gas circulated externally around the polycarbonate milling vial containing stainless steel rods. SEM/EDS and TEM/EDS mapping analyses revealed the presence of some Si embedded in the Al-rich particles and some existed as free Si. As expected, with increasing MA and sequential milling (MA + CM) duration, strain values increased and crystallite sizes decreased. Si solubility in α-Al was enhanced with increasing MA durations and utilizing MA and CM consecutively (sequential milling) as indicated by DSC endothermic and XRD peak shifts. A maximum solubility of 2.25 at.% Si in α-Al or Si solid solubility extension of 0.65 at.% was estimated for the Al12.6Si eutectic alloy powders MA’d for 8 h.

Influence of the fabrication process of copper matrix composites on cavitation erosion resistance

Copper matrix composites reinforced with ZrB2 particles were produced in two ways: by hot pressing (HP) and laser-sintering process. Powder mixture Cu-Zr-B was mechanically alloyed before densification processes. Variations in the microstructure of treated samples obtained during cavitation test were analyzed by scanning electron microscopy (SEM). Cavitation erosion resistance was investigated with the standard test method for cavitation erosion using vibratory apparatus. Changes in mechanical alloying duration show a strong influence on cavitation erosion resistance of Cu–ZrB2 composites regardless the number of reinforcements. Laser-sintered samples show better cavitation erosion resistance than hot-pressed samples.

Effect of synthesis parameters on structural and mechanical properties of Ti3Al–Nb–Mo intermetallic compound obtained by powder metallurgy techniques

The influence of microstructure, heat treatment and alloying addition on mechanical and fracture properties of Ti3Al-based intermetallic at room and elevated temperatures was studied. Ti3Al–11Nb–1Mo (mole fraction, %) alloy was consolidated via powder metallurgy processing by mechanical alloying (MA) and hot pressing (HP). MA powders were characterized using XRD and SEM-EDS. Optimum MA duration was 25 h and HP conditions of 1350 °C, 2 h, 35 MPa. After HP, solution treatment at 1050 °C for 1 h and water quenching α2+β Widmanstätten microstructure is present, while subsequent aging at 800 °C during 24 h induces small content of O-phase. High fraction of β-phase is a direct consequence of Mo. Compression tests were performed from room temperature to 750 °C in vacuum. The yield strength of compacts increases with temperature up to 250 °C (pyramidal slip systems activation), after which it decreases. Ductility increases throughout the whole temperature range. The presence of O phase contributed to ductility increase in aged alloys, while negligibly lowering yield strength. Registered drop in the yield strength of aged alloys compared with non-aged ones was mostly influenced by precipitation of α″2 particles. Mixed fracture modes are operative at all temperatures.

Processing and characterization of graphene nano-platelet (GNP) reinforced aluminum matrix composites

AbstractAluminum matrix composites containing graphene nano-platelets (GNPs) as reinforcement additive were fabricated by a two-step process consisting of mechanical alloying and pressureless sintering. The effects of graphene nano-platelets amounts and mechanical alloying duration on the microstructural and mechanical properties of aluminum were investigated. The characterization studies were performed by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy/energy dispersive spectrometry, particle size analysis, differential scanning calorimetry, Archimedes' density and microhardness test method. The microhardness of composites increased gradually by the addition of 0.5 and 1 wt.-% GNP, whereas an adverse effect was observed by the increment of the GNP amount to 2 wt.-%.

Electrochemical characterization of mechanically alloyed LaCaMgNi9 compound

The performance of a nickel–metal hydride (Ni–MH) battery mainly depends on the characteristics of the negative electrode. The electrochemical characteristics of mechanically alloyed compound LaCaMgNi9, including the discharge capacity and the hydrogen diffusion coefficient, were studied as function of mechanical alloying (MA) conditions. The electrochemical measurements show that the LaCaMgNi9 electrode has a maximum discharge capacity of about 150 mAh/g at a discharge rate of C/3. The hydrogen discharge capacity dramatically decreases as MA duration exceeds 20 h.

Influence of mechanical alloying on surface layer of P/M AISI 316L powder with addition of FeNiMnSiB master alloy

In this study, the microstructure, structure, and thickness of the surface layer, sintering process, and homogeneity of the distribution of elements of sintered AISI 316L with the addition of FeNiMnSiB master alloy were tested. The master alloy was introduced both by mixing and by a mechanical alloying process. This paper describes the influence of the duration of mechanical alloying on the sintering behaviour of 316L stainless steel powder with the addition of FeNiMnSiB master alloy. Dilatometric, calorimetric, Scanning Electron Microscopy, Light Optical Microscopy, microstructural, hardness, and microhardness tests were performed to estimate the influence of chemical modification and mechanical alloying time on the material properties. Special attention was paid to the surface densified layer. It was found that mechanical alloying has a significant influence on the starting temperature of the sintering process, microstructure, and distribution of elements. The addition of the master alloy allowed a more equally distributed surface dense layer to be obtained. The thickness of the surface layer of high density changed as the duration of mechanical alloying increased. The layer was compared to one created by the addition of elemental boron.

Determination of crystallite size, strain and solubility in mechanically alloyed W-xTi (x=0.5, 1.0, 4.0 and 10.0 wt%) powder alloys

Effects of mechanical alloying (MA) and titanium (Ti) content on the effective lattice parameter, crystallite size and lattice strain of the W-xTi (x=0.5, 1.0, 4.0 and 10.0wt% Ti) alloys were investigated. Using TOPAS 5 (Bruker AXS) software and Vegard's law, effective lattice parameters, aeff were determined from the X-ray diffraction (XRD) peak shift values at different MA durations and Ti contents. Lattice strain and crystallite sizes at varying MA durations and Ti contents were calculated by the Williamson-Hall method and Lorentzian rule using the TOPAS 5 (Bruker AXS) software. As expected, with increasing MA durations and Ti contents, effective lattice parameter and strain values increased and crystallite sizes decreased. Deviations of measured effective lattice parameter values from Vegard's law were analyzed. Negative deviations from the Vegard's law exist for the W-xTi (x=0.5, 1.0, 4.0 and 10.0wt% Ti) alloys MA'd for 10h and a maximum solubility of 11at% Ti was estimated for the W-10wt%Ti alloy MA'd for 10h. The smallest crystallite size of 2.21nm and the maximum strain of 4.57% were calculated for the W-4wt%Ti alloy MA'd for 20h.

XRD characterization of mechanically alloyed high-nitrogen nanocrystalline Fe–Cr system

The effect of milling time on defect structure and phase composition of nanostructured Fe–25Cr–10Mn–1N (wt%) alloy powders processed by mechanical alloying (MA) in the high energy planetary ball mill under argon atmosphere was investigated using X-ray diffraction (XRD) and Mössbauer spectroscopy. For this purpose the powder mixture of iron, chromium and manganese nitride Mn2N was used. The consecutive deformation dissolution of chrome and manganese nitride in bcc Fe and phase transformation from bcc (ferrite) to fcc (austenite) with the formation of fully austenitic structure for 8h of MA took place. Using the differential scanning calorimetry it was shown that the chromium nitride Cr2N precipitates and a partial reverse fcc to bcc transformation occurs during the heating of mechanically alloyed austenite in the temperature range of 600°C. The anisotropic (hkl-dependent) position shifts of Bragg bcc reflections increasing with MA duration were observed. These anisotropic shifts together with the observed anisotropic broadening of reflections were reasonably attributed to the appearance of certain type of stacking faults on {211} and {310} planes of bcc phase during MA. It was assumed that the stacking faults play an important part in the deformation bcc to fcc transformation under MA of high-nitrogen Fe–Cr system.

Mechanical alloying of aluminum alloy by nanodiamond particles

The shape, dimension, and microhardness of Al-2Cu-1,6Mn-0,4Zr (wt. %) based composite material powders hardened by nanodiamond particles in amount of 0–10 vol. % depending on mechanical alloying duration have been investigated. The maximum run time in planetary ball mill is 15 h. Mean pellet size of composite materials obtained with the use of chip matrix particles of 1000 μm in size is shown to decrease up to 30 μm when mechani- cal alloying time increases. In the course of mechanical alloying the material microhardness rises to 270–320 HV.

Mechanical alloying of aluminum alloy with nanodiamond particles

The shape, size, and microhardness of composite materials based on an Al-2Cu-1.6Mn-0.4Zr alloy (wt %) reinforced with nanodiamond particles in an amount of 0–10 vol % depending on the duration of mechanical alloying (MA) are investigated. The maximal treatment time in a planetary mill is 15 h. It is shown that, as the MA time increases, the average granule size of composite materials fabricated using chips matrix particles of about 1000 μm in size decreases to 30 μm. During MA, the material microhardness increases to 270–320 HV.

Structural, mechanical and magnetic properties of Fe — 40-at.% Al powders during mechanical alloying

Nanocrystalline Fe — 40at.% Al alloy powders were prepared by using a mechanical alloying (MA) process with a planetary high-energy ball mill. The structural and the morphological properties of the powders were investigated by means of X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. A disordered Fe(Al) solid solution with bcc crystal structure was formed after 10 h of MA. Longer MA durations introduced ordering in the alloyed powders. The final crystallite size was found to be as small as 5 nm whereas the internal strain was found to reach a final value of 2.1%. Also, the lattice parameter quickly increased to a maximum value of 0.2926 nm at 30 h of MA, and then decreased to a value of 0.2873 at 80 h of MA. SEM results showed variations in the shapes and the sizes of the particles in the powders at different stages. Furthermore, the microhardness values were found to increase gradually with increasing MA time due to work hardening, grain refinement and solid-solution formation. Magnetic properties such as the saturation magnetization (Ms) and the coercive field (Hc) were calculated from the hysteresis loops, and the results are presented as functions of the MA time.

Influence of TiB2 particle size on the microstructure and properties of Al matrix composites prepared via mechanical alloying and pressureless sintering

Abstract In this study, TiB 2 particulate reinforced Al matrix composites were fabricated with the incorporation of both micron- and submicron-scale TiB 2 particles by a combined method of mechanical alloying, cold pressing and pressureless sintering. Commercial TiB 2 powders with an average particle size of 40 μm were milled to 320 nm for 12 h in a high-energy ball mill. The effects of TiB 2 particle size (40 μm and 320 nm), TiB 2 content (5, 10 and 15 wt.%) and mechanical alloying duration (2, 4 and 8 h) on the microstructural and properties of the Al matrix composites were investigated. The composites reinforced with submicron TiB 2 particles exhibited higher hardness (in the vicinity of 2 GPa for 15 wt.% reinforcement) and lower relative wear resistance values compared to those reinforced with micron-scale TiB 2 particles. Furthermore, hardness and relative wear resistance values of the composites increased with increasing TiB 2 contents. Density and hardness values of the sintered samples has uncertain tendency in regard of different mechanical alloying durations. Microstructures of the micron- and submicron-scale TiB 2 reinforced Al matrix composites contain homogeneously dispersed fine- and ultrafine-grained TiB 2 particles and an amount of Al 3 Ti flakes.

Characterization Investigations of W-Ni Matrix Composites Reinforced with TiB2and La2O3

W 1 wt% Ni (W1Ni) matrix composites reinforced with TiB2 and La2O3 particles were fabricated via mechanical alloying and activated sintering methods. Powder blends with compositions of W1Ni 2 wt% TiB2 x wt% La2O3 (x = 0.5, 1) were mechanically alloyed for 6 and 12 h. The results showed that increase in mechanical alloying duration to 12 h causes the decline of grain sizes of the W Ni matrix to nanoscales. TiB2/La2O3 particles have a signi cant e ect on the density/microhardness values and wear amounts of the sintered samples.

Effects of La<sub>2</sub>O<sub>3</sub> Addition on the Microstructure and Properties of Activated Sintered W-Ni Compacts

In order to improve the properties of Ni activated sintered W compacts, La2O3 was added to a W-1 wt.% Ni matrix alloy. W-1 wt.% Ni-0.5 wt.% La2O3 and W-1 wt.% Ni-1 wt.% La2O3 composites were fabricated by mechanical alloying and activated sintering methods. The effects of La2O3 content and mechanical alloying duration on the microstructural and physical properties of activated sintered W-Ni compacts were investigated. The results showed that La2O3 particles have a significant effect on the density/microhardness values and wear amounts of the samples. The relative density value of 96.39 % and microhardness value of 4.08±0.28 GPa of W-1 wt.% Ni samples increased to respectively 98.09 % and 5.45±0.29 GPa with the addition of 1 wt.% La2O3. Wear rate of 3.26±0.81 (mm3N-1m-1)x10-9 of the W-1 wt% Ni samples decreased to 2.10±0.24 (mm3N-1m-1)x10-9 with the addition of 0.5 wt.% La2O3. Furthermore, grain sizes decreased and microhardness values increased with increasing mechanical alloying duration.