Influence Of Mechanical Alloying Research Articles

Thermodynamic and Kinetic Simulations Used for the Study of the Influence of Precipitates on Thermophysical Properties in NiTiCu Alloys Obtained by Spark Plasma Sintering.

The thermodynamic and kinetic simulations based on the re-assessment of the thermodynamic and kinetic database of the Ni-Ti-Cu system were employed to predict the phenomena of mechanical alloying, spark plasma sintering and thermal properties of the intriguing Ni-Ti-Cu system. Thermodynamic calculations are presented for the stable and unstable phases of NiTiCu materials and support a correlation with the evolving microstructure during the technological process. Also, the thermal conductivity, the thermal diffusivity and the specific heat of spark plasma sintered and aged Cu-alloyed NiTi-based shape memory alloys (NiTiCu) with two compositions, Ni45Ti50Cu5 and Ni40Ti50Cu10, are evaluated and the influence of mechanical alloying and precipitates on thermal properties is discussed. Measurements of these thermal properties were carried out from 25 °C up to 175 °C using the laser flash method, as well as differential scanning calorimetry. The thermal hysteresis of the 20 mm diameter samples was between 8.8 and 24.5 °C. The observed T0 temperatures from DSC experimental transformation features are in reasonable accordance with the thermodynamic predictions. The determined k values are between 20.04 and 26.87 W/m K and in agreement with the literature results. Moreover, this paper can provide some suggestions for the preparation of NiTiCu shape memory alloys and their applications.

Influence of mechanical alloying on structural, thermal, and magnetic properties of Fe50Ni10Co10Ti10B20 high entropy soft magnetic alloy

Influence of mechanical alloying on structural, thermal, and magnetic properties of Fe50Ni10Co10Ti10B20 high entropy soft magnetic alloy

Influence of mechanical alloying on the particle size, microstructure and soft magnetic properties of coarse Fe-based amorphous powders prepared by gas atomization

The aim of this work is to refine the particle size of the coarse Fe-based amorphous powders by ball milling process without destroying the amorphous characteristics, thermal stability and soft magnetic properties. The gas atomized Fe-based amorphous powders were sieved, and the powders larger than 75 μm were selected as the raw materials. The effects of ball milling on the particle size, morphology, amorphous rate, thermal stability and soft magnetic properties of the Fe-based amorphous powders were systematically investigated. The results showed that the particle size of the Fe-based amorphous powders decreased as the ball milling time increased, and the mass median diameter (D50) of the powders was reduced by almost 80% after ball milling of 9 h compared with that of the initial powders (D50 reduced from 138.4 μm to 24.22 μm). The nanocrystallization and amorphization induced by the microstructural breakdown and intensified inter-diffusion of elements during the ball milling improved the amorphous rate of Fe-based powders. The ball milling reduced the saturation magnetization of the Fe-based amorphous powders, and had little effect on the coercivity. As a result, ball milling not only refined the particle size, but also improved the amorphous phase content of the Fe-based amorphous powders without changing the thermal stability and soft magnetic properties.

Spark plasma sintering of Fe–Si–B–Cu–Nb / Finemet based alloys

The influence of mechanical alloying (MA) and spark plasma sintering (SPS) processing parameters on the microstructure, magnetic and mechanical properties of Finemet (Fe73.5Cu1Nb3Si13.5B9) type alloys was investigated. Finemet alloy powder was obtained via mechanical alloying of elemental powders for 30 h, 60 h, 90 h, and 120 h with ball to powder ratio (BPR) of 10:1 and 15:1. The milled powders were consolidated using the SPS process. The XRD patterns confirm the presence of the α-Fe3Si phase in all Finemet alloys, also broadening of the (110) peak of α-Fe3Si was observed with increasing milling time. The microhardness of Finemet alloys increases with increase in milling time primarily due to a decrease in grain size. All samples show good saturation magnetization (Ms), 120h sample exhibiting the highest Ms of 166 emu/g, however coercivity increases with increasing milling time. Additionally, α-Fe3Si crystal size decreases with increasing the BPR primarily due to higher impact energy.

Influence of Mechanical Alloying and Sintering Temperature on the Microstructure and Mechanical Properties of a Ti-22Al-25Nb Alloy

In this research, a fine-grained Ti-22Al-25Nb (at.%) alloy was fabricated from the powders of Ti, Al and Nb by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). The effects of MA and SPS parameters on the microstructure, micro-hardness and tribological properties of the sintered compacts were investigated and discussed. The single phase of (Ti, Al, Nb) bcc solid solution with the chemical composition of Ti-22Al-25Nb was produced by MA for 5-20 h and the rotation speed of 500 rpm. The mechanically alloyed powders for 5, 10, 15 and 20 h were subsequently consolidated by SPS at the temperature range of 1000-1300 °C for 60 min, respectively, followed by furnace cooling. The microstructures from the sintered compacts showed that the fine equiaxed B2 phase, the lamellar or equiaxed O phase, and the equiaxed α2 phase were present in all the sintered compacts. The highest micro-hardness value of 1840 HV0.3 and the smallest wear rate of 1.59 × 10−3 mm3/m were exhibited in the Ti-22Al-25Nb alloy sintered at 1100 °C/60 min/50 MPa.

Influence of mechanical alloying and extrusion conditions on the microstructure and tensile properties of Low-Cr ODS FeCrAl alloys

Low-chromium (<10%Cr) high strength oxide dispersion strengthened (ODS) FeCrAl alloys are considered promising candidates for accident tolerant fuel cladding in light water fission reactors. These alloys are designed to combine the beneficial high temperature mechanical properties of ODS materials with the exceptionally high temperature oxidation resistance of FeCrAl in comparison to conventional Zr-containing cladding materials, while also providing good mechanical and aqueous corrosion behavior under normal light water reactor operating conditions. The initial (1st generation) ODS FeCrAl alloys combined gas atomized FeCrAl powders with yttria and other oxides for alloying element additions using the mechanical alloying approach. These alloys exhibited low ductility but excellent high temperature tensile strength while maintaining good oxidation resistance at temperatures up to 1400 °C. In an attempt to improve alloy ductility for accident tolerant fuel cladding applications, new low-Cr ODS FeCrAl alloys with decreased oxygen content were developed with the Zr alloying solute already gas atomized into the powder prior to mechanical alloying. The resultant Fe-10Cr-6.1Al-0.3Zr+0.3Y2O3 (106ZY) powders were ball milled for 10, 20, and 40hr followed by consolidation via hot extrusion at temperatures ranging from 900 to 1050 °C. Increasing the mechanical alloying time decreased the resultant grain size and improved high temperature tensile properties. Decreasing the extrusion temperature refined the grain size and subsequently strengthened the ODS FeCrAl 106ZY alloys while lowering the ductility. Scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS) demonstrated the Zr solute addition effectively sequestered impurity C and N within the matrix. The root mean square (RMS) hardening superposition model for yield strength shows good agreement with experimental results. Errors between predicted and experimental values are discussed within the scope of processing parameters. These 2nd generation 106ZY alloys show a distinct increase in alloy ductility without sacrificing the high temperature tensile properties characteristic of legacy or 1st generation ODS FeCrAl alloys.

Influence of mechanical alloying and heat treatment processing on the Ni2MnSn Heusler alloy structure

Formation of the Ni2MnSn Heusler alloy by solid state reaction from elemental powders was investigated. The solid state reaction was conducted in a planetary ball mill under argon atmosphere up to 28 h of milling. During the milling, after selected intervals samples were collected and studied by X-ray diffraction to record phase changes. After 16 h of milling a two phase mixture (Ni2MnSn with B2 structure and NiMnSn with C1b structure) was found. Further, the thermal stability of the samples was investigated, and phase precipitation was found. The formed phases are ordered Full Heusler (L21) and Ni3Sn2. The formation temperature and their amount evolution versus temperature and milling time is discussed. An inversion of the formation temperature was found for the L21 and Ni3Sn2 phase, during the DSC study, in relation with the milling time. For the B2 compound a stability range on temperature was identified (from 25 to 300 °C), as well as for the L21 and Ni3Sn2 phases (from 400 to 600 °C) in the case of 28 h milled sample. The milled and annealed sample exhibit nanocrystalline state, formation mechanism under temperature was concluded to be by precipitation.

Influence of mechanical alloying on the microstructure and mechanical properties of powder metallurgy Ti2AlNb-based alloy

A fine grained Ti2AlNb-based alloy with a high strength was fabricated from elemental powders by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). The effects of MA parameters on the microstructure and mechanical properties of the mechanically alloyed powder and sintered compacts were investigated. The single phase of (Ti, Al, Nb) bcc solid solution with a normal composition (mole fraction, %) of 53 Ti, 22 Al and 25 Nb was produced by MA for 40h/400rpm. The mechanically alloyed powder was subsequently synthesized by SPS at 1150°C/10min/35MPa followed by furnace cooling. The microstructure of the sintered alloy consisted of fine grained B2-matrix, ultrafine acicular O-phase inside B2-matrix, and ultrafine equiaxed α2-phases along the rim of B2-matrix. The yield strength and ultimate strength of the alloy sintered from the 40h mechanically alloyed powder were 1644MPa and 2542MPa in the compression test, respectively. Meanwhile, the strains to failure at room temperature and 650°C were 31.3% and 55.3%, respectively.

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.

Microstructure of 08KH18N10T Austenitic Steel Mechanically Alloyed with Nanooxides of the Y2O3 – ZrO2 System

We study the influence of mechanical alloying with nanopowders of 80%Y2O3 –20% ZrO2 oxide on the microstructure of 08Kh18N10T austenitic steel. It is shown that mechanical alloying, cold compaction, and thermomechanical treatment of compacts lead to the formation of precipitates with predominantly crystal structure of Y2(Ti1−x Zr x )2O7 -type oxides in steel. They are characterized by a high density (~7 · 1021m–3), a mean size of ~10 nm, and semicoherent boundaries with the austenitic matrix.

SHS in the Nb–Si system: Influence of mechanical alloying

Influence of mechanical alloying (MA) on SHS in low-caloric Nb–2Si mixtures was explored as a function of MA time and Si content of green mixtures. The use of MA was found to extend the concentration limits for combustion synthesis in the Nb–Si system to the following range: between 43 wt % Si–57 wt % Nb and 10 wt % Si–90 wt % Nb. Due to MA, SHS in Nb–Si blends can be carried out in a mode of solid–solid or liquid–solid reaction.

Microstructure of mechanically alloyed and annealed Al62Cu25.5Fe12.5 powder

The influence of mechanical alloying (MA) of Al62Cu25.5Fe12.5 (at.%) powder obtained with different milling speeds and milling time and subsequent annealing on its microstructure and phase composition was investigated by means X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM) methods. The power was milled in a high energy planetary ball mill at the rotation speed 250, 300 and 350 rpm for 3, 6, 10 and 20 h using WC milling media. The annealing of milled powders was performed at 800 °C for 4 h. Nano-quasicrystalline icosahedral phase (i-phase) was obtained in the as-milled powder at a speed 350 rpm, while the lower milling speed resulted in the formation of cubic β-Al(Cu, Fe) phase. In all annealed powders the i-phase coexisting with the ordered β-Al(Cu, Fe) phase and small amount of the λ-Al13Fe4 phase has been observed. The highest volume fraction of i-phase was found in the annealed powder milled at 250 rpm. After annealing the grain size increases compared to the as-milled powder.

Gas release during combustion of Ti + 2B films: Influence of mechanical alloying

Influence of mechanical alloying on gas release during combustion of Ti + 2B films was studied experimentally. The volume of released gas and the rate of gas evolution were measured as a function of mechanoactivation duration and ambient atmosphere. Burning velocity of Ti + 2B films and gas release rate were found to depend on a volume of gas released during combustion, type of environment, and MA conditions. The results may turn useful for optimizing combustion synthesis of titanium diboride and related materials as well as for some pyrotechnic applications.

Influence of Mechanical Alloying on Dielectric Features of Ferroelectric BaTiO3 Microcrystals

Influence of Mechanical Alloying on Dielectric Features of Ferroelectric BaTiO3 Microcrystals

Influence of Mechanical Alloying on the Behavior of Fe-Mn-Si-Cr-Ni Shape Memory Alloys Made by Powder Metallurgy

Fe-14 Mn-6 Si-9 Cr-5 Ni (mass. %) shape memory alloys (SMAs) were produced from raw powders employed both in initial commercial state and in a mixture state of equal fractions of commercial and mechanically alloyed (MA’d) particles. After blending, pressing and sintering, powder compacts were hot rolled (HR’d) and solution treated (ST’d) before being machined into plane-parallel lamellas. Specimens with special geometry were pre-strained on a tensile testing machine. By means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) the presence of ε hexagonal close packed and α’ body center cubic stress induced martensites was revealed and their thermally induced reversion to γ face center cubic austenite was evaluated by modulated differential scanning calorimetry (MDSC). The results enabled the study of the influence of MA, HR, ST and pre-straining on phase structure and associated on shape memory effect (SME). The lamellas were hot formed into rings, which were trained in bending. Diameter reduction of trained enlarged rings, on heating, was monitored by cinematographic analysis.

Influence of mechanical alloying on Ti3SiC2 formation via spark plasma sintering technique from Ti/SiC/C powders

Abstract Ti 3 SiC 2 was elaborated by two different methods: (i) Spark plasma sintering of 5Ti/2SiC/C powders and (ii) mechanical alloying of powders followed by Spark plasma sintering. The results showed that mechanical alloying was not advantageous for pure Ti 3 SiC 2 formation but it can significantly improve the density of the obtained bulk material via the particles refinement as well as the microhardness by increasing the TiC content. It was found that the relative density was increased up to 98.58% for the sintered mechanically alloyed sample whereas it was not more than 96.04% for the sintered 5Ti/2SiC/C starting powders. The Vickers microhardness measured for both bulk samples demonstrates a high improvement for the previously mechanically alloyed powder mixture, as it was of about 1282 Hv and only 581.2 Hv for the alloy obtained from 5Ti/2SiC/C starting powders.

Self-propagating high-temperature synthesis (SHS) of rotator mixed and mechanically alloyed Ni/Al powder compacts

A significant amount of work has been published on the combustion synthesis of nickel aluminides including thermal explosion and SHS type of ignition, [1–4]. In the SHS of nickel aluminides, nickel and aluminum powders are mixed in the desired composition and pressed into a compact, which is then ignited at one end, usually with the aid of a tungsten-heating coil (Fig. 1). An exothermic reaction proceeds converting the nickel and aluminum powders into the desired intermetallic compound, and raises the compact temperature to the maximum combustion temperature. The elemental powders are normally turbula or rotator mixed prior to compaction. On the other hand, recently, mechanical activation of elemental powders prior to SHS (mechanically activated SHS (MASHS)) has also been conducted [5–9]. In MASHS the powders are mechanically alloyed by ball milling under certain conditions that do not give rise to reactions between the elemental powders. In this process nanostructured elemental powders are generated prior to SHS. The process has a number of advantages including the production of a nanostructured product phase; however the resulting product is reported to contain high levels of porosity attributed to entrapped gas during the mechanical alloying process [10]. In the present paper, the concepts of the theory of plasticity of porous bodies are employed to assess the influence of mechanical alloying (MA) on the theoretical yield stress of Ni–Al powder compacts (for nickel particle sizes of 8–15 and 3–7 lm). The effect of MA (low-energy mechanical mixing) on SHS characteristics are reported, together with the influence of degassing-MA-SHS sequential order on resulting product porosity, which may possibly have implications for MASHS in general. Powders of nickel (Novamet Inc., USA) and aluminum ()325 mesh, average particle size ~11 lm, Atlantic Engineers, USA), were mixed in the composition of Ni3Al. Two sample compositions were produced, each with a different nickel particle size (3–7 and 8–15 lm, respectively). For each composition, mixing was conducted over two stages. First, the powders were gently mixed for 1.5 h using a powder rotator mixer. Second, approximately 5–6 g of Ni/Al powders were separately mechanically alloyed (low-energy mechanically mixed) in hardened steel vials, using twenty tungsten carbide balls (diameter 3 mm) at 240 rpm for 27 h. Specimens that have just been mixed using the powder rotator without MA are referred to in this paper as have undergone rotator mixing. Powders that were rotator mixed followed by MA for 27 h are referred to as MA 27 h. Each powder was then uniaxially pressed into rectangular specimens of dimensions shown in (Fig. 1). Zinc stearate lubricant was mixed in acetone and applied to the inner walls of the hardened steel compaction die used. All powder compacts were vacuum degassed at 150 C for 10.5 h. A K-type thermocouple was inserted at half height into the specimen to monitor the temperature– time profile during the reaction. Specimens were then reacted in an SHS reactor under an argon atmosphere (three specimens were used for each particle size and mixing sequence, and average combustion temperatures were then reported). The top of the specimens were placed at a distance approximately 2–3 mm beneath the tungsten coil, which was subsequently subjected to 750 W. Each powder mixture (mechanically alloyed and K. Morsi (&) AE S. Shinde AE E. A. Olevsky Department of Mechanical Engineering, San Diego State University, 5500 Campanile Drive, San Diego, California 92182, USA e-mail: kmorsi@mail.sdsu.edu J Mater Sci (2006) 41:5699–5703 DOI 10.1007/s10853-006-0068-x

Effect of nickel particle size on the compaction behavior of rotator mixed and mechanically alloyed nickel and aluminum powders

Elemental powder mixing prior to processes such as self-propagating high temperature synthesis (SHS) is a vital processing step that needs careful consideration. This is particularly true for powders with submicron particle sizes. The present paper investigates the effect of mechanical alloying of mixtures of aluminum and nickel (with different nickel particle sizes) on the dispersion and cold compaction behavior of the composite powders. The concepts of the theory of plasticity of porous bodies are also employed to assess the influence of mechanical alloying (MA) on the theoretical yield stress of the composite powder compact. It was found that after mechanical alloying, the yield stress increased only for nickel powder sizes equal to and greater than 5 μm.

The influence of mechanical alloying on the structural and physical properties of YNi4B compound

We have investigated the influence of mechanical milling on structural changes, magnetic and superconducting properties of YNi4B compound. This compound crystallizes in a hexagonal structure with the P6/mmm space group. Magnetic measurements have shown that originally prepared sample exhibits superconducting behaviour below 12 K and above this temperature the sample is paramagnetic. The great decrease of intensity and broadening of diffraction lines have been detected after milling as a consequence of sample amorphisation.

The influence of mechanical alloying on the magnetic properties of U−Co−B system

We have investigated the influence of mechanical milling on structural changes and magnetic properties of the uranium transition-metal boride UCo4B intermetallic compound. The great decrease of intensity and broadening of diffraction lines have been detected after milling as a consequence of amorphisation of samples. Magnetic measurements have shown that originally prepared polycrystalline sample shows properties of Pauli paramagnet with spin fluctuations. After milling the magnetic ordered state has been observed and high value of high-field susceptibility can be attributed to the itinerant character of investigated samples. The changes of magnetic moment during the milling processes can be attributed to the fact that probability of environment typical to the crystalline state is lowered.