ULTRAFINE PRIMARY SILICON PARTICLES IN PHOSPHORUS-MODIFIED HYPEREUTECTIC AL-SI ALLOY POWDERS PRODUCED BY SAMD METHOD

2008 ◽  
Vol 22 (18n19) ◽  
pp. 3304-3310 ◽  
Author(s):  
P. DELSHAD-KHATIBI ◽  
F. AKHLAGHI
Keyword(s):  
Primary Silicon ◽  
Powder Particle Size ◽  
Primary Si ◽  
Solid Media ◽  
Aluminum Droplets ◽  
Rotating Impeller ◽  
Powder Particles ◽  
Size And Morphology ◽  
Phosphorus Modification ◽  
Average Size

In the present study, alloy powder batches of Al-20Si (wt. %) were generated by SAMD technique using NaCl as the solid media. The method consists of introducing and mixing a specified amount of NaCl particles (mean diameter 254 μm) in aluminum melt at the temperature of 710°C. Melt disintegration occurs in 5 min by kinetic energy transfer from a rotating impeller (1400 rpm) to the metal via the solid atomizing medium ( NaCl particles). The resulting mixture of aluminum droplets and NaCl particles are subsequently quenched in water to dissolve NaCl and solidify Al droplets to produce powder particles. In order to investigate the effect of phosphorus modification on the size and morphology of the primary Si particles, the SAMD technique was also performed to produce Al-20Si -0.015P powder particles. The resultant powders were screened through 6 different sized sieves ranging from 38 to 500 μm and different powder fractions were cold mounted, polished and studied by optical microscopy. It was concluded that for both un-modified and modified alloys, there was a decrease in the size of primary Si particles corresponding to a decrease in the powder particle size. However, the same sized phosphorus modified powders exhibited considerably finer primary Si particles in which the average size of these ultrafine Si particles was about 1.1 μm for the smallest sieved particles.

Solution-SBR Powders

1976 ◽  
Vol 49 (1) ◽  
pp. 126-139
Author(s):  
D. N. Schulz ◽  
L. E. Calihan ◽  
D. P. Tate
Keyword(s):  
Powder Particle Size ◽  
Factors Affecting ◽  
Molecular Weights ◽  
Bound Rubber ◽  
Powder Blends ◽  
Powder Particles ◽  
Filler Dispersion ◽  
Particle Size And Morphology ◽  
Size And Morphology ◽  
Powdered Rubber

Abstract This paper describes the advantageous cross-fertilization of solution-masterbatch technology and powdered-rubber processing. A nonlatex method has been developed for the preparation of free-flowing solution-SBR powders. The factors affecting powder particle size and morphology have been identified. Optimization of the preparative variables has resulted in dry-blendable solution-SBR powders. As a consequence of a low shear history, the solution-SBR powder blends show distinctive rubber-filler, rheological, and physical properties. For example, unvulcanized solution-SBR powder compounds evince higher molecular weights and lower bound-rubber contents than conventional mixes. Yet, the microscopic filler dispersion of these two types of compounds appears similar. Uncured solution-SBR powder blends also exhibit stiffer rheological behavior than conventional mixes. Furthermore, this stiffness tends to persist in the vuleanizates derived from these powdered compounds. Vulcanizate excellence depends primarily upon fineness of the powder particles and absence of free filler. Conditions have been found which permit the direct ribbon extrusion of tire tread, without prior compacting or milling. Conventional single-screw ribbon- tread extruders are sufficient to produce treads of high quality.

Investigation on Feedstock Preparation for Micro-Cemented Carbide Injection Molding

2018 ◽  
Vol 18 (2) ◽  
pp. 96-102
Author(s):  
Abdolali Fayyaz ◽  
Norhamidi Muhamad ◽  
Abu Bakar Sulong
Keyword(s):  
Flow Behavior ◽  
Flow Characteristics ◽  
High Viscosity ◽  
Cemented Carbide ◽  
Solid Loading ◽  
Powder Particle Size ◽  
Powder Particles ◽  
Particle Size And Morphology ◽  
Size And Morphology ◽  
Feedstock Preparation

Abstract This research was focused on mixing of submicron cemented carbide (WC-Co-VC) powder and binder. WC-Co-VC powder particle size and morphology were analyzed by laser diffraction and field emission scanning electron microscopy. The WC-Co-VC powder was kneaded with a paraffin wax based binder system. Based on critical solid loading, the feedstock with different solid loadings between 49 to 51 vol.% was prepared. Finally, the flow behavior of different feedstocks was investigated. Morphology of powder revealed that the particles of powder are slightly agglomerated and irregular in shape. The result of mixing indicted that the torque value increases as the solid loading increase from 49 vol.% to 51 vol.%. The feedstock exhibited homogeneity and the powder particles are homogenously coated with binder. The feedstock with solid loading of 51 vol.% is sensitive to temperature and showed high viscosity values. The feedstock with solid loadings of 49 and 50 vol.% had good compatibility and flow characteristics.

Investigation on the Primary Si Phase Solidification and the Properties of SiCw/Al-18Si Composites

2007 ◽  
Vol 353-358 ◽  
pp. 1275-1278
Author(s):  
Lin Geng ◽  
Hong Mei Wei ◽  
Xue Xi Zhang
Keyword(s):  
Squeeze Casting ◽  
Volume Fraction ◽  
Primary Silicon ◽  
Solidification Behavior ◽  
Scanning Calorimetry ◽  
Solidification Temperature ◽  
Casting Technique ◽  
Microstructure Observation ◽  
Primary Si ◽  
Average Size

SiCw/Al-18Si composites were prepared by squeeze casting technique. SiCw/Al-18Si composites were remelted before solidification. The effects of volume fraction of SiC whisker on solidification behavior of SiCw/Al-18Si composites were investigated by means of differential scanning calorimetry (DSC) technique and microstructure observation. DSC results indicated that the start solidification temperature and primary silicon peak temperature decreased gradually and the degree of supercooling increased with the increasing of SiC whisker content. SiC whisker and Sr decreased the average size of Si phases and improved the mechanical properties of the composites.

scholarly journals High Bending Strength Hypereutectic Al-22Si-0.2Fe-0.1Cu-Re Alloy Fabricated by Selective Laser Melting

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 528
Author(s):  
Chunyue Yin ◽  
Zhehao Lu ◽  
Xianshun Wei ◽  
Biao Yan ◽  
Pengfei Yan
Keyword(s):  
Selective Laser Melting ◽  
Bending Strength ◽  
Primary Silicon ◽  
Processing Parameters ◽  
Powder Materials ◽  
Laser Melting ◽  
Maximum Value ◽  
Fine Microstructure ◽  
Average Size ◽  
Al Matrix

The objective of the study is to investigate the corresponding microstructure and mechanical properties, especially bending strength, of the hypereutectic Al-Si alloy processed by selective laser melting (SLM). Almost dense Al-22Si-0.2Fe-0.1Cu-Re alloy is fabricated from a novel type of powder materials with optimized processing parameters. Phase analysis of such Al-22Si-0.2Fe-0.1Cu-Re alloy shows that the solubility of Si in Al matrix increases significantly. The fine microstructure can be observed, divided into three zones: fine zones, coarse zones, and heat-affected zones (HAZs). Fine zones are directly generated from the liquid phase with the characteristic of petaloid structures and bulk Al-Si eutectic. Due to the fine microstructure induced by the rapid cooling rate of SLM, the primary silicon presents a minimum average size of ~0.5 μm in fine zones, significantly smaller than that in the conventional produced hypereutectic samples. Moreover, the maximum value of Vickers hardness reaches ~170 HV0.2, and bending strength increases to 687.70 MPa for the as-built Al-22Si-0.2Fe-0.1Cu-Re alloys parts, which is much higher than that of cast counterparts. The formation mechanism of this fine microstructure and the enhancement reasons of bending strength are also discussed.

scholarly journals Influence of reducing agents and surfactants on size and shape of silver fine powder particles

2014 ◽  
Vol 20 (2) ◽  
pp. 73-88 ◽  
Author(s):  
Stevan P. Dimitrijević ◽  
Željko Kamberović ◽  
Marija Korać ◽  
Zoran Anđić ◽  
Silvana Dimitrijević ◽  
...  
Keyword(s):  
Chemical Reduction ◽  
Nitrate Solution ◽  
Fine Powder ◽  
Production Scale ◽  
Scale Reduction ◽  
Primary Particles ◽  
Powder Particles ◽  
Different Shapes ◽  
Average Size ◽  
Scanning Electron

Silver fine powder with different shapes and sizes were prepared by chemical reduction and characterized by scanning electron microscope. In this paper was presented the method for the preparation of the fine Ag powder with particles size smaller than 2.5 µm with suitability for the mass-production scale. Reduction was performed from nitrate solution directly by vigorous stirring at room temperature by three different reduction agents, with and without presence of two dispersants. Scanning electron microscopy revealed the preferred size of the particles obtained in all experiments with aim of the protecting agent. Larger particles and wider size distribution were obtained without surfactants although with average size of about 1 µm and small quantity of larger clusters of primary particles that is out of the fine powder classification. High purity, 99.999%, of silver was obtained in every experiment. 

Study on the Influence of Different Pulse Temperatures on Al-22%Si Alloy Solidification Structure

2011 ◽  
Vol 299-300 ◽  
pp. 566-571
Author(s):  
Zuo Fu Zhao ◽  
Jian Zhong Wang ◽  
Jin Gang Qi ◽  
Shan Dai ◽  
Dong Jun Zhang
Keyword(s):  
Volume Fraction ◽  
Electric Pulse ◽  
Primary Silicon ◽  
Electrical Pulse ◽  
Solidification Structure ◽  
Alloy Solidification ◽  
Modification Effect ◽  
Electric Pulse Modification ◽  
Average Size

Taking the hypereutectic Al-Si alloy as the research object, the fading characteristics of Al-22% Si alloy at different pulse temperatures are investigated in this paper in order to analyze the mechanism of electrical pulse modification to the alloy. We can get the conclusion by observing the microstructure of the sample, measuring the microhardness and calculating the volume fraction and the average size of primary silicon: at different pulse temperatures, the effect of electric pulse modification is fading with static duration prolonging; meanwhile, with the temperature upward, the modification effect and fading trends to be weak, which indicates the best pulse temperature is one of the important factors to influence the modification effect.

Research on the Densification Process of the Mechanically-Alloyed Amorphous 2Si-B-3C-N Powder

2018 ◽  
Vol 281 ◽  
pp. 15-21
Author(s):  
Peng Fei Zhang ◽  
De Chang Jia ◽  
Bin Yang ◽  
Guang Xin Wang
Keyword(s):  
Mechanical Properties ◽  
Hexagonal Boron Nitride ◽  
Amorphous Powder ◽  
Silicon Powder ◽  
Graphite Powder ◽  
Densification Process ◽  
Mechanically Alloyed ◽  
Powder Particles ◽  
Average Size ◽  
N Powder

A mixture of the commercially available cubic silicon powder, hexagonal boron nitride powder and graphite powder was mechanically alloyed to prepare amorphous 2Si-B-3C-N composite powder. The amorphous powder was heated up to 1900°C in nitrogen, with a heating rate of 20°C/min and under a pressure of 80 MPa. Careful investigation was carried out on the densification curve, the microstructure and the mechanical properties of the prepared ceramics. Results show that the amorphous 2Si-B-3C-N powder mainly consists of near-spherical agglomerates, with an average size of 3.5±2.4 micrometers. When the amorphous powder was hot pressed, the densification process mainly included three stages, the denser packing of powder particles with the help of axial pressure, the initial sintering at about 1500-1800°C, and the rapid sintering at temperatures approximately higher than 1830°C. When the 2Si-B-3C-N ceramic was hot pressed at 1900°C for 10-30 mins, it exhibited large volume shrinkage, noticeable reduction of pores, and significantly improvement of density and mechanical properties. The applied high temperature and large pressure may give rise to severe plastic deformation, viscous flow and creep of powder particles, which greatly contribute to the rapid densification of the amorphous 2Si-B-3C-N powder.

Influence of the Powder Particle Size on the Denudated Zone Width at Selective Laser Melting

2020 ◽  
Vol 989 ◽  
pp. 816-820
Author(s):  
Roman Sergeevich Khmyrov ◽  
R.R. Ableyeva ◽  
Tatiana Vasilievna Tarasova ◽  
A.V. Gusarov
Keyword(s):  
Particle Size ◽  
Selective Laser Melting ◽  
Powder Particle ◽  
Powder Particle Size ◽  
Adhesion Forces ◽  
Laser Melting ◽  
Friction Forces ◽  
Single Bead ◽  
Powder Particles

Mass transfer in the laser-interaction zone at selective laser melting influences the quality of the obtained material. Powder particles displacement during the formation of the single bead is experimentally studied. The so-called denudated zone was visualized by metallography. It was determined that increasing the powder particle size leads to widening the denudated zone. This can signify that the adhesion forces between powder particles prevail over the friction forces.

Influences of Complex Modification of RE and P on the Microstructure and Impact Toughness of Hypereutectic Al-24Si Alloy

2010 ◽  
Vol 152-153 ◽  
pp. 1328-1332
Author(s):  
Niu Can Liu ◽  
Hai Dong Li ◽  
Zhong Xia Liu
Keyword(s):  
Impact Toughness ◽  
Eutectic Silicon ◽  
Primary Silicon ◽  
Initiation Energy ◽  
Unmodified Alloy ◽  
Average Size ◽  
The Impact

The influences of RE and P complex modification on microstructure and impact toughness of hypereutectic Al-24Si alloy are investigated. The result shows that the coarse block primary silicon is refined obviously and its edges and angles are blunted under the influences of the complex modification of RE and P. The large needle eutectic silicon is modified to the short-rod or particle ones also. The alloys have the finest microstructure and highest impact toughness when adding about 0.10% P and 0.9% RE into alloys. Compared with the unmodified alloy, the average size of primary silicon in the modified alloys refined from 93.5μm to 24.1μm and the impact toughness of alloys increases to 11.0062J/cm2 from 7.3572J/cm2. The excellent impact toughness of alloys can be attributed to the increase of initiation energy and expand energy of the cracks caused by the refinement of primary silicon and eutectic silicon after complex modified with P and RE.

Synthesis and Characterization of 3Y-TZP by Gel Solid-State Method

2011 ◽  
Vol 412 ◽  
pp. 61-64
Author(s):  
Xiao Bo Wu ◽  
Da Zhi Sun ◽  
Dan Yu Jiang ◽  
Hai Fang Xu ◽  
De Xin Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid State ◽  
Sintering Behavior ◽  
X Ray Diffraction ◽  
Solid State Method ◽  
X Ray ◽  
Powder Particles ◽  
State Method ◽  
Average Size

3Y-TZP powder has been successfully synthesized by gel solid-state method. The structural phases of powder particles were analyzed by X-ray diffraction and the morphology was analyzed by scanning electron microscopy. The average size of grains was 230 nm. The sintering behavior, mechanical properties and microstructure of 3Y-TZP ceramics sintered by this powder were investigated. The experiment results showed that the mechanical properties of ceramics were excellent.

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