Effect Of Process Control Agent Research Articles

Evolution of Morphology, Particle Size and Oxidation Resistance of Recycled Ti-6Al-4V Powders Prepared by Planetary Ball Milling

AbstractPlanetary ball milling is a high-energy ball milling technique that is widely used for the synthesis of alloy and composite powders with micrometer or nanometer particle sizes. The effect of process control agent (PCA) content (wt%) and milling time on the morphology, particle size and distribution, crystallite structure, apparent density and oxidation resistance of recycled T-6Al-4V alloy powders from lathe chips is investigated in this study. To investigate the effect of the PCA on the properties of the Ti-6Al-4V alloy particles, methanol is used as the PCA in various amounts of 0.5, 1 and 2 wt%. The milling is carried out using 20:1 of ball-to-powder ratio (BPR) and 400 rpm of milling speed. A morphological change from scrap form to flake-like shape, from flake-like morphology to irregular and semispherical shape and finally from semispherical form to spherical morphology is observed with increase in milling time for all PCA ratios. The results showed that the average particle sizes (D50) are 20, 18.1 and 21.8 μm after milling of 360 min with 0.5 wt%, 1 wt% and 2 wt% PCA, respectively. Results show that the most suitable recycled Ti-6Al-4V powders for powder-based manufacturing techniques are produced between 180 and 360 min of milling with 2 wt% PCA.

Effect of process control agent on the synthesis of Cu-Y2O3 by mechanical alloying

Two types of Cu composites containing 3 wt% Y2O3, with and without a process control agent (PCA), were fabricated using mechanical alloying (MA) and hot isostatic pressing (HIP). The results showed that the addition of PCA effectively inhibited the growth of MA powders. This was attributed to the PCA forming a lubricating film on the MA powders, preventing adhesion between the powders. However, residual PCA after heat treatments contained C impurities, which had a significant impact on thermal conductivity. The lubricating film weakened the binding force between MA powders during sintering, resulting in poor mechanical performance. Additionally, the lubricating film slowed down the MA process by eliminating the frictional stress caused by oblique collision. Frictional stress plays a crucial role in the dissolution of Y into the Cu matrix due to the tearing of Y-rich particles and the fracture of MA powders. Therefore, it is necessary to explore an optimum PCA that can be easily removed before sintering, slow down the growth of MA powders, and avoid reducing the efficiency of the MA process during the synthesis of Cu-Y2O3 composites by mechanical alloying.

The Effect of Process Control Agent and Milling Time on the Solid-State Recycling by Mechanical Milling of Ti-6al-4v Alloy Scraps

The Effect of Process Control Agent and Milling Time on the Solid-State Recycling by Mechanical Milling of Ti-6al-4v Alloy Scraps

Effect of Process Control Agent on Microstructures and High-Temperature Oxidation Behavior of a Nickel-Based ODS Alloy

Two nickel-based oxide-dispersion-strengthened (ODS) alloys supplemented with different amounts of process control agent (PCA) were prepared. The microstructures including grains and nanometric oxides and the subsequent oxidation behavior of these ODS alloys were investigated. It was found that the distribution of nanometric oxides in the nickel-based ODS alloy is uniform and the grains are refined by adding a proper amount of PCA in the mechanical milling, while the blocking effect on the diffusion of active elements Y, Al and Ti among powders takes place with an excessive amount of PCA, resulting in the precipitation of large-size oxides in local areas of the alloy. After oxidation in air at 1000 °C for 200 h, the oxide scales on the surface of both nickel-based ODS alloys are composed of Cr2O3. As Y-rich oxide particles are precipitated in the matrix, the thickness of the oxide scale is significantly reduced compared with non-ODS alloys. However, due to the influence of grain boundaries on the diffusion of elements, the oxide scale on the surface of an alloy with finer grain size is thicker. The oxidation resistance of ODS alloys strongly depends on the exact manufacturing process.

Effect of Process Control Agents on Fe-15at.%Nb powder during Mechanical Alloying

In this paper, Fe-15at.%Nb alloys were produced from high purity Fe (min. 99.8%) and Nb (min. 99.8%) powders via a mechanical alloying process. The effects of different Process Control Agents (i.e., methanol, hexane, and stearic acid) were investigated with powder morphologies, particle size distribution, and phase formation, and were sampled after up to 80 milling hours at 350 rpm. The powder morphologies and particle sizes were evaluated using scanning electron microscopy and laser diffraction analysis, respectively, and phases were identified via X-ray powder diffractometry. The results demonstrate for all conditions that, in the early stages, there was significant particle agglomeration due to the ductile-ductile feature of Fe and Nb powders, and latter an amorphization trend up to 80 milling hours. Methanol was the most efficient Process Control Agent in terms of avoiding cold welding, reducing of agglomeration, particle size distribution, reducing contamination and crystallinity reduction rate.

Effect of process control agents on mechanically alloyed Al0.3CoCrFeNi

The current work reports the effect of methanol and toluene process control agents (PCAs) on mechanical alloying of Al0.3CoCrFeNi high entropy alloy. The milling time was optimized to 5 h which leads to formation of face-centred-cubic (major) and body-centred-cubic phases (minor). Subsequent annealing gives pure fcc phase with Cr7C3 as a contaminant from the PCA. Methanol gives lesser contamination ~4% compared to toluene ~11%. Spark plasma sintering of the optimized sample yields density of 96% with fine grain size ~ 1.5 µm and annealing twins, all of which contribute to higher hardness ~ 425 HV0.5 in the samples.

Effect of process control agent and mechanical milling on the embedment and uniform dispersion of CNTs and B4C in aluminium matrix

Using lighter materials like Aluminium(Al) is also a common practice for producing prosthetic devices. This method not only provides less weight but also gives freedom to the designer to design customized devices. But Al can not be used in its pure form as it lacks strength, toughness, rigidity. A common way to overcome these issues is the use of composite materials.In this paper, we have studied how mechanical milling can be used to disperse hard ceramic particles and Carbon nanotube homogenously in Al matrix. We have also demonstrated how changes in different process parameters affect the properties of this composite and how a uniform dispersion can be achieved by the use of the specialized technique. In this paper, we have also suggested methods to avoid clustering and cold welding of reinforcements.

The high-energy milling process as a synergistic approach to minimize the thermal conductivity of PbTe nanostructures

The mechanochemical synthesis of PbTe nanostructures via the high-energy milling (HEM) process is proposed, as a synergistic approach, to minimize the thermal conductivity of this semiconductor material at room temperature. In this study, the effect of process control agent (PCA) addition on the microstructure and thermal properties of the as-milled PbTe nanostructures was also investigated. The synthesis design is based on a solid-state technique which allows enhancing the grain boundary scattering and consequently, decreases the thermal conductivity in the PbTe nanostructures. Moreover, the challenging part is the formation of coarse particles with embedded quantum dots and nanoparticles, which are expected to scatter long- and mid-wavelength phonons. In this sense, via the HEM-process, it is feasible to activate other phonon scattering modes by introducing rough-surfaced grains and nanoroughness to the particle surfaces. Overall, the thermal conductivity is decreased in the PbTe nanostructures by two means; namely, adding scattering processes and phonon group velocity, which were heightened due to the PCA added during milling. To elucidate the role of these components of the phonon thermal conductivity, atomic force microscopy and high-resolution transmission electron microscopy were used. On the other hand, photoacoustic (PA) and photopyroelectric (PP) techniques were applied to study the thermal properties of the PbTe nanostructures obtained by the HEM-process. The total thermal conductivity values of the PbTe nanostructures obtained by the PA and PP techniques were at least a half lower (1.06 W m−1 K−1) than that of bulk PbTe value counterpart (∼2.13 W m−1 K−1) and lower than those from PbTe nanomaterials (ranging from 1.5 to 2.2 W m−1 K−1) obtained via other means. The thermal conductivity values of the as-milled PbTe nanostructures were closely related to the carrier concentration experimental findings. We inferred that this strategy can be widely applicable to enhance existing thermoelectric compounds into their nanoforms by a scalable and a simple low-cost route.

Effects of Process Control Agents on Characteristics of Cu-Ta Nanocomposite during Milling and Subsequent Sintering

Effects of type and concentration of process control agent on characteristics of the nanocrystalline Cu-1Ta nanocomposite during milling and subsequent sintering were investigated. Microstructural analyses showed that addition of stearic acid (SA) into Cu-1Ta mixture was more effective compared to toluene. The results revealed that application of 2% SA provided a significant dissolution of Ta in Cu lattice after milling for 32 h; however, the extended milling encouraged Ta rejection and increased the crystallite size. Reduction of SA to 1% resulted in a narrower crystallite size distribution with mean size of 18.5 nm. The mechanical and physical tests also indicated that addition of 1% SA rather than 2% toluene caused an increase of 33% in electrical conductivity with nearly no change in micro-hardness.

Effect of Process Control Agent on the Microstructure of Ni-Based ODS Superalloy Produced by Mechanical Alloying and Sintering

Effect of Process Control Agent on the Microstructure of Ni-Based ODS Superalloy Produced by Mechanical Alloying and Sintering

Effect of process control agent on alloying and mechanical behavior of L21 phase Ni–Ti–Al alloys

In this paper, we manufacture Ni50Ti25Al25 alloys dominated by L21-Ni2TiAl phases using mechanical alloying (MA) technique. The effects of process control agent (PCA) on MA process and mechanical properties of the Ni–Ti–Al alloys are investigated. It is found that the present L21-Ni50Ti25Al25 alloy exhibits high hardness, low reduced modulus and excellent pseudoelasticity. The PCA directly affects the MA process, microstructure and mechanical properties of the alloys. The MA sample without adding PCA has higher strength and much lower alloying temperature than that with PCA. Based on the nanoindentation tests, hardness of the both alloys showed obvious indentation depth dependence. Meanwhile a transition from normal indentation size effect of nano-hardness to reverse indentation size effect is observed.

The effect of process control agents and milling atmosphere on the structural changes of Ti50Cu27,5Ni10Zr10Co2,5 master alloy during short time milling

Properties of powders made from Ti50Cu27,5Ni10Zr10Co2,5 alloy, milled under different conditions for only 3600 s in total were investigated. For this purpose two different milling atmospheres and two different Process Control Agents (PCA) were tested: argon without PCA, air without PCA, argon combined with stearic acid, argon combined with petroleum spirit. Results showed that the size and shape of particles, and the microstrucutre and hardness of partcicles were highly depended on the milling conditions. According to XRD analysis, the maximal amorphous fraction has been achieved in the air atmosphere withouth PCA milled sample (57 wt. %) powder. However the extent of Fe contamination and weight loss during milling powder resulted bigger values. As a result, the optimal combination of morphology, contamination amount and weight lost level has been observed in the case of powder milled in argon atmosphere using stearic acid.

The Effect of Process Control Agent on the Oxidation of Nanocrystalline Mechanically Alloyed AlCoCrFeMnNi Powders

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Effect of Process Control Agent on a Mechanically Milled Pure Aluminum sample

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Effect of process control agent on the structural and magnetic properties of nano/amorphous Fe0.7Nb0.1Zr0.1Ti0.1 powders prepared by high energy ball milling

In this study, amorphous Fe0.7Nb0.1Zr0.1Ti0.1 alloy without metalloids was produced by mechanical alloying of pure mixture elements. Miedema’s semi-empirical model was employed to predict the possibility of amorphous phase formation in proposed alloying system. The effect of Hexane as process control agent (PCA) on the structural, magnetic, morphological and thermal properties of the products was investigated. The results showed that the presence of PCA was necessary for the formation of amorphous phase as well as improved its soft magnetic properties. The PCA addition causes an increase of the saturation magnetization (about 43%) and decrease of the coercivity (about 50%). Moreover, the sample milled without PCA, showed a wide particle size distribution as well as relatively spherical geometry. While, in the presence of PCA the powders were aspherical and Polygon. In addition, the crystallization and Curie temperatures were found to be around 800 °C and 650 °C, respectively which are relatively high values for these kinds of alloys.

Effects of Process Control Agents on the Mechanical Alloying Behavior of Nb-Ti-Si Based Alloy

Effects of Process Control Agents on the Mechanical Alloying Behavior of Nb-Ti-Si Based Alloy

Effect of high energy ball milling on the structure of iron — multiwall carbon nanotubes (MWCNT) composite

High energy ball milling is employed to produce iron matrix- multiwall carbon nanotube (MWCNT) reinforced composite. The damage caused to MWCNT due to harsh ball milling condition and its influence on interfacial bonding is studied. Different amount of MWCNT is used to find the optimal percentage of MWCNT for avoidance of the formation of chemical reaction product at the matrix - reinforcement interface. Effect of process control agent is assessed by the use of different materials for the purpose. It is observed that ethanol as a process control agent (PCA) causes degradation of MWCNT reinforcements after milling for two hours whereas solid stearic acid used as process control agent, allows satisfactory conservation of MWCNT structure. It is further noted that at a high MWCNT content (~ 2wt.%), high energy ball milling leads to reaction of iron and carbon and forms iron carbide (cementite) at the iron-MWCNT interface. At low percentage of MWCNT, dissolution of carbon in iron takes place and the amount of reinforcement in iron matrix composite becomes negligibly small. However, under the present ball milling condition (ball to metal ratio~ 6:1 and 200 rpm vial speed) iron-1wt.% MWCNT composite of good interfacial bonding can retain the tubular structure of reinforcing MWCNT.

Erratum: “Effects of process control agents on the synthesis of nano-crystalline barium hexaferrite”

Nano size particles of barium hexaferrite were produced by conventional mixed oxide ceramic method from BaCO3 and αFe2O3 as starting materials with a Fe/Ba molar ratio of 11. The mixture of precursors was intensively milled by high energy ball mill and the The influence of various process control agents (PCA) on the process has been investigated. Analysis of the XRD patterns indicates that PCA can strongly alter the morphology and phase composition of ball milled powder particles. In all milled samples, BaCO3 completely decomposed and slight displacement of reflections of hematite phase due to the dissolving of various ions like Ba or C in its lattice is observed. Nano size particles exhibiting angular shape together with some amorphous structure were observed in the sample processed in the presence of NaCl. Barium hexaferrite magnetic phase was partially formed in sample milled in the presence of stearic acid.

Effect of Process Control Agents on the FeSiB Powder Amorphisation by Wet Mechanical Alloying

Result of research concerning the influence of milling conditions on the amorphisation of the Fe75Si20B5 (at.%) alloy is presented. Amorphous powder of Fe75Si20B5 (at.%) was prepared by dry and wet mechanical alloying (MA) route starting from a mixture of Fe, Si and B elemental powders. The mixture was wet/dry milled up to 50 hours. Benzene, oleic acid and ethanol were used as process control agents (PCA) in order to investigate the influence of their chemical composition on the powder amorphisation. The evolution of the powder crystalline structure, thermal stability and magnetic properties were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) as well as magnetic measurements versus temperature and field. It is proved that the chemical composition of the PCA (especially the carbon content) plays an important role in the amorphisation process induced by wet MA.

Optimization of milling parameters for the synthesis of nano-structured duplex and ferritic stainless steel powders by high energy planetary milling

Abstract Nano-structured duplex and ferritic stainless steel powders were prepared by high energy planetary milling of elemental Fe, Cr and Ni powders. Here, we have studied the effect of process control agent (PCA) such as stearic acid (SA), effect of ball to powder weight ratio (BPR 6:1and 12:1) and milling speed (64% and 75% critical speed) during planetary milling of elemental Fe–18Cr–13Ni (duplex) and Fe–17Cr–1Ni (ferritic) powders for 10 h in a dual drive planetary mill (DDPM). We have found that all these milling parameters have great influence in tuning the final particle morphology, size and phase evolution during milling. It was found that addition of PCA, a BPR of 12:1 and 75% critical speed is more effective in reducing particle size and formation of duplex and ferritic stainless steel after 10 h milling of elemental powder compositions than their counterparts. The particle size of duplex and ferritic stainless steel milled in the presence of SA for 10 h is found to be 13 and 14 μm, whereas the particle size is 20 and 16 μm without SA respectively. The particle size of powder milled at 12:1 BPR is lower than powder milled at 6:1 BPR because of more impact energy induced by balls on powders and it is found to be 10 and 12 μm respectively for duplex and ferrite in presence of SA. The median particle size of duplex and ferritic stainless steel milled at 75% critical speed is found to be 3.5 and 2.4 μm respectively.