Statics and kinematics of granular materials

Mechanical alloying/milling technique is characterized by the repeated welding and fracturing of powder particles in a high-energy ball mill, which often results in excessive cold welding and agglomeration of ductile particles. To achieve the critical balance between cold welding and fracturing, the surface of the deforming particles is modified by introducing a suitable organic material, called surfactant or process control agent (PCA). However, the use of surfactants is self-contradictory by nature and requires further consideration of the milling variables and type/amount of surfactant. The current article provides a practical approach to the promises and challenges associated with surfactants in mechanical alloying/milling. An attempt has been made to address the most crucial aspects correlated with surfactants, including contamination, the morphology and size of powder particles, formation of alloy and microstructural evolution, and powder yield, as well as the physico-mechanical properties, such as ...

Surfactants in Mechanical Alloying/Milling: A Catch-22 Situation

Spark plasma sintering of graphitized multi-walled carbon nanotube reinforced Ti6Al4V

漏洩磁場測定による溶接管のオンライン検査(Non-Destructive Testing,9-1,1976)(文献紹介)

Industries use metal-matrix composites all year round, where the alloying of metals plays an important role. Many researchers have seen that an improvement in the alloying of metals possesses a great value in applications. So metal-matrix composites are being investigated for better blending of the particles for the metal constituents. This guides researchers towards the addition of many alloying elements or reinforcements to form superior-quality MMCs with smaller particle sizes. In this regard, the focus of the present work is to reinforce alumina with copper synthesized and blended using a high-energy ball milling. The powders were compressed by cold compaction at a pressure of 174 MPa and sintered at 950 °C. Separate green compacts were formed from each of the powders that were milled for different time periods, such as (3, 6, 9, 12, 15) h. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine the particle size of the powders and the dominant processes during the milling, respectively. The wear and corrosion behaviours of each specimen were investigated in accordance with the ASTM G99-17 and ASTM G44-99 standards, respectively. The results clearly show that as the particle sizes of the powders reduce, the wear and corrosion rates decrease. The properties were found to be the best for the compacts formed from powders milled for 12 h.

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Variations in the properties of copper-alumina nanocomposites synthesized by mechanical alloying

Synopsis This paper reports the results of a study to determine the effect of process control agent (PCA) on the characteristics of Ti-Mg powders during milling. It has been shown that a 2% increase in PCA content leads to up to a 40% increase in yield of the milled powder but reduces the kinetics of the mechanical alloying process. The

/pdf/effect-of-process-control-agent-pca-on-the-characteristics-41g6a1hh3n.pdf

Effect of process control agent (PCA) on the characteristics of mechanically alloyed Ti-Mg powders

In order to reliably design and operate different powder processes, an understanding of the dynamic flow, shear and bulk properties of powders is required. Generally, powders are evaluated by several techniques that determine their flow, shear and bulk properties. The techniques can include compression tests, shear tests, angle of repose, flow of powder in a funnel, tapped density and many others. In order to minimize the number of instruments required to characterise the powder and eliminate operator error, automated powder rheometers that can do most of the required tests have been developed. The FT4 powder rheometer is one of these and has found widespread use in the pharmaceutical industry. In this study, the FT4 powder rheometer was used to characterise two metallic titanium powders with different particle sizes, namely CSIR Ti-45μm (Fine Powder) and CSIR Ti +45-180μm (Coarse Powder). Their particle size, particle size distribution, bulk densities, compressibility, cohesion, flowability index, effective angle of internal friction and wall friction angle were determined. Preliminary results of the study indicated that fine powder had a lower bulk density, was more compressible and more cohesive than the coarse powder. The fine powder had a lower flowability index compared to the coarse powder for both the Jenike and Peschl classification. The varying degrees of cohesion of these powders were confirmed by the cohesion values that were higher for the fine powder. The fine powder had a lower angle of internal friction but higher wall friction angle compared to the coarse powder.

Characterisation of Titanium Powder Flow, Shear and Bulk Properties Using the FT4 Powder Rheometer

The Southern African Institute of Mining and Metallurgy Advanced Metals Initiative Light Metals Conference 2010, Misty Hills, Muldersdrift, 27–29 October 2010

Effect of process control agent (PCA) on the characteristics of mechanically alloyed Ti-Mg powders [Conference paper]

Determination of tensile properties of materials is required to reliably predict performance of engineering materials in service and for design purposes. Tensile properties are also used as a measure of product quality. Various testing standards recommend specific specimen sizes for reporting of tensile properties. This recommendation is normally a challenge in materials development where the required specimen size is not achievable due to component size limitation. In addition, the materials developer still wants to compare their tensile results with the reference materials produced from standard sizes or produced from different geometries. It is well documented that tensile properties are affected by the specimen geometry (gauge length and cross sectional area). It is therefore the purpose of this study to investigate the effect of specimen geometry on tensile properties. In addition, this study seeks to determine suitable specimen geometry required to yield comparable tensile properties obtained from other specimen geometries. Various dog bone specimen geometries were produced from a titanium alloy metal sheet and tensile properties determined. Yield strength, Ultimate tensile strength and, % elongation were compared. Yield strength and ultimate tensile strength were not affected by different specimen geometries. However, % elongation differed for different geometries.

https://iopscience.iop.org/article/10.1088/1757-899X/430/1/012015/pdf

Silethelwe Chikosha

Papers

Effect of process control agent (PCA) on the characteristics of mechanically alloyed Ti-Mg powders

Characterisation of Titanium Powder Flow, Shear and Bulk Properties Using the FT4 Powder Rheometer

Effect of process control agent (PCA) on the characteristics of mechanically alloyed Ti-Mg powders [Conference paper]

The effect of specimen geometry on tensile properties of titanium alloy metal sheet.

Machine learning-based prediction of phases in high-entropy alloys: A data article.