Preparation and Characterization of Tungsten Heavy Alloy Feedstock for Metal Injection Molding

2007 ◽  
Vol 26-28 ◽  
pp. 363-366 ◽  
Author(s):  
Syed Humail Islam ◽  
Xuan Hui Qu ◽  
M. Tufail
Keyword(s):  
Molecular Weight ◽  
Stearic Acid ◽  
High Density Polyethylene ◽  
Flow Behavior ◽  
Metal Injection Molding ◽  
Tungsten Heavy Alloy ◽  
Shear Rates ◽  
Heavy Alloys ◽  
Tungsten Heavy Alloys

In this study, the effect of various binders’ compositions on the feedstock of pre-alloyed tungsten heavy alloys (WHAs) powders has been investigated. Four kinds of wax-based binders were prepared from paraffin wax (PW), high-density polyethylene (HDPE), polypropylene (PP) and stearic acid (SA), and the characteristic of each feedstock was investigated at various temperatures and shear rates. It was found that all the feedstocks exhibited pseudoplastic flow behavior. Feedstock having multi-polymer components showed better rheological properties than those having mono-polymer because of good wettability between powder and binder, and less sensitivity to temperature and shear rates. This could be due to the molecular weight and length of molecular chain of PP and HDPE.

scholarly journals Effects of Sintering Conditions on Structures and Properties of Sintered Tungsten Heavy Alloy

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2338 ◽  
Author(s):  
Lenka Kunčická ◽  
Radim Kocich ◽  
Zuzana Klečková
Keyword(s):  
Sintering Temperature ◽  
Heavy Alloy ◽  
Tungsten Heavy Alloy ◽  
Fabrication Technology ◽  
Sintering Time ◽  
Heavy Alloys ◽  
Structures And Properties ◽  
Processing Step ◽  
Tungsten Heavy Alloys ◽  
Subsequent Quenching

Probably the most advantageous fabrication technology of tungsten heavy alloys enabling the achievement of required performance combines methods of powder metallurgy and processing by intensive plastic deformation. Since the selected processing conditions applied for each individual processing step affect the final structures and properties of the alloys, their optimization is of the utmost importance. This study deals with thorough investigations of the effects of sintering temperature, sintering time, and subsequent quenching in water on the structures and mechanical properties of a 93W6Ni1Co tungsten heavy alloy. The results showed that sintering at temperatures of or above 1525 °C leads to formation of structures featuring W agglomerates surrounded by the NiCo matrix. The sintering time has non-negligible effects on the microhardness of the sintered samples as it affects the diffusion and structure softening phenomena. Implementation of quenching to the processing technology results in excellent plasticity of the green sintered and quenched pieces of almost 20%, while maintaining the strength of more than 1000 MPa.

INFLUENCE OF SPACE HOLDER ON RHEOLOGICAL BEHAVIOR OF COPPER FEEDSTOCKS FOR METAL INJECTION MOLDING

2015 ◽  
Vol 76 (6) ◽  
Author(s):  
Mohammad Dahar Kamal Bahrin ◽  
Nor ‘Aini Wahab ◽  
Nor Amalina Nordin ◽  
Muhammad Hussain Ismail ◽  
Ismail Nasiruddin Ahmad
Keyword(s):  
Injection Molding ◽  
Rheological Behavior ◽  
Flow Behavior ◽  
Palm Stearin ◽  
Metal Injection Molding ◽  
Plastic Behavior ◽  
Flow Behavior Index ◽  
Space Holder ◽  
Porous Copper

The characterization of MIM feedstock consisting of 63 vol% of copper powder with a binder system consisting of palm stearin (PS) and low density polyethylene (LDPE) was studied. To achieve porous structure, sodium chloride (NaCl) was added as a space holder. The effect of shear rate (s-1), temperature (oC) and viscosity (Pa.s) on the rheological behavior of solid and porous copper feedstocks were investigated by using the Rosand RH2000 Capillary Rheometer at temperatures of 160, 170 and 180oC. The feedstocks achieved desirable injection molding characteristics such as pseudo-plastic behaviour, stable flow, flow behavior index less than 1 (n<1) and low activation energy (E). It can be concluded from the analysis that both feedstocks showed a good pseudo-plastic behavior within acceptable ranges in MIM. 

Fabrication and Characterization of High-density Polyethylene - Coconut Coir Composites with Stearic Acid as Compatibilizer

2009 ◽  
Vol 23 (3) ◽  
pp. 361-373 ◽  
Author(s):  
Joseph King Eos Dawn V. Enriquez ◽  
Peter June Macalino Santiago ◽  
Timothy Funcion Ong ◽  
Soma Chakraborty
Keyword(s):  
Stearic Acid ◽  
High Density Polyethylene ◽  
High Density ◽  
Fabrication And Characterization ◽  
Coconut Coir

scholarly journals Effect of Ti on Microstructure and Properties of Tungsten Heavy Alloy Joint Brazed by CuAgTi Filler Metal

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1057
Author(s):  
Yuzhen Lu ◽  
Xiaoming Qiu ◽  
Ye Ruan ◽  
Cui Luo ◽  
Fei Xing
Keyword(s):  
Shear Strength ◽  
Room Temperature ◽  
Filler Metal ◽  
Active Element ◽  
Tungsten Heavy Alloy ◽  
X Ray ◽  
Heavy Alloys ◽  
Tungsten Heavy Alloys ◽  
Poor Area ◽  
Ti Content

In this paper, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD) were used to comprehensively analyze the microstructure and brazing performance of a CuAgTi filler metal with braze tungsten heavy alloys. The association of microstructure, wettability and shear strength of brazing joints was also investigated. With the addition of Ti, the Ti3Cu4 phase appeared in the microstructure of filler metal. Ti is active element that promotes the reaction of filler with tungsten. Therefore, the Ti element is enriched around tungsten and forms a Ti2Cu layer at the interface, leaving a Cu-rich/Ti-poor area on the side. Remaining Ti and Cu elements form the acicular Ti3Cu4 structure at the center of the brazing zone. The wettability of filler metal is improved, and the spreading area is increased from 120.3 mm2 to 320.9 mm2 with the addition of 10 wt.% Ti. The shear strength of joint reaches the highest level at a Ti content of 2.5 wt.%, the highest shear strength is 245.6 MPa at room temperature and 142.2 MPa at 400 °C.

Rheological Properties of Polybutadienes Prepared by n-Butyllithium Initiation

1965 ◽  
Vol 38 (4) ◽  
pp. 881-892
Author(s):  
J. T. Gruver ◽  
Gerard Kraus
Keyword(s):  
Molecular Weight ◽  
Shear Rate ◽  
Flow Behavior ◽  
Average Molecular Weight ◽  
Polymer System ◽  
Newtonian Flow ◽  
Newtonian Viscosity ◽  
Long Chain Branching ◽  
Shear Rates ◽  
Molecular Weights

Abstract The flow behavior of n-butyllithium-polymerized polybutadienes was investigated as a function of molecular weight, temperature, and shear rate. At low shear rates these polymers exhibit Newtonian flow up to molecular weights of several hundred thousand so that “zero shear” Newtonian viscosities can readily be determined without the risk of long extrapolation. Above 10,000 molecular weight the Newtonian viscosities obey the well-known 3.4 power dependence on weight-average molecular weight. The entanglement spacing molecular weight is estimated at 5600. The temperature dependence of viscosity is substantially independent of molecular weight and shear stress and can be represented analytically by functions proposed in the literature. The apparent activation energy for viscous flow is not constant, but decreases with rising temperature. The flow of the polymers becomes increasingly non-Newtonian with the product of shear rate, molecular weight and Newtonian viscosity. However, the departure from Newtonian behavior is apparently less than for any polymer system whose flow behavior has been described in the literature. The indications are, therefore, that sharp molecular weight distribution and freedom from long chain branching favor Newtonian flow and that the n-butyllithium initiated polybutadienes represent some of the most perfectly linear, narrow distribution polymers known.

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