scholarly journals Workability Behaviour of Powder Metallurgy Aluminium Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Narayan ◽  
A. Rajeshkannan
Keyword(s):  
Free Surface ◽  
Powder Metallurgy ◽  
Relative Density ◽  
Least Square ◽  
Fracture Criteria ◽  
Sintered Compact ◽  
Experimental Values

An efficient way to find the workability limit for powder metallurgy parts has been suggested. Compacts of Al-4%TiC, Al-4%WC, Al-4%Fe3C, and Al-4%Mo2C were produced to the relative density of 0.82 and 0.86 with three different geometries through primary operations of powder metallurgy routes. Each sintered compact was hot deformed to various strain levels till a visible crack appeared at the free surface. Oyane’s fracture principle was used to develop a theory to study powder metallurgy compacts. A least square technique was used to determine the constants in fracture criteria and these equations were finally used to find workability limit. It is found that the projected technique was well in agreement with the experimental values.

scholarly journals Dynamic Stress and Displacement in an Elastic Half-Space with a Cylindrical Cavity

2011 ◽  
Vol 18 (6) ◽  
pp. 827-838 ◽  
Author(s):  
İ. Coşkun ◽  
H. Engin ◽  
A. Özmutlu
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Half Space ◽  
Cylindrical Cavity ◽  
Circular Cross Section ◽  
Elastic Half Space ◽  
Least Square ◽  
Polar Coordinates ◽  
Wave Number ◽  
Forcing Function

The dynamic response of an elastic half-space with a cylindrical cavity in a circular cross-section is analyzed. The cavity is assumed to be infinitely long, lying parallel to the plane-free surface of the medium at a finite depth and subjected to a uniformly distributed harmonic pressure at the inner surface. The problem considered is one of plain strain, in which it is assumed that the geometry and material properties of the medium and the forcing function are constant along the axis of the cavity. The equations of motion are reduced to two wave equations in polar coordinates with the use of Helmholtz potentials. The method of wave function expansion is used to construct the displacement fields in terms of the potentials. The boundary conditions at the surface of the cavity are satisfied exactly, and they are satisfied approximately at the free surface of the half-space. Thus, the unknown coefficients in the expansions are obtained from the treatment of boundary conditions using a collocation least-square scheme. Numerical results, which are presented in the figures, show that the wave number (i.e., the frequency) and depth of the cavity significantly affect the displacement and stress.

Studies on Preparation of Ti3SiC2 Particulate Reinforced Cu Matrix Composite by Warm Compaction and Its Tribological Behavior

2007 ◽  
Vol 534-536 ◽  
pp. 929-932 ◽  
Author(s):  
Tungwai Leo Ngai ◽  
Zhi Yu Xiao ◽  
Yuan Biao Wu ◽  
Yuan Yuan Li
Keyword(s):  
Electrical Conductivity ◽  
Powder Metallurgy ◽  
Relative Density ◽  
Matrix Composite ◽  
Copper Matrix ◽  
High Density ◽  
Green Density ◽  
Warm Compaction ◽  
Copper Matrix Composite ◽  
Particulate Reinforced

Conventional powder metallurgy processing can produce copper green compacts with density less than 8.3 g/cm3 (a relative density of 93%). Performances of these conventionally compacted materials are substantially lower than their full density counterparts. Warm compaction, which is a simple and economical forming process to prepare high density powder metallurgy parts or materials, was employed to develop a Ti3SiC2 particulate reinforced copper matrix composite with high density, high electrical conductivity and high strength. In order to clarify the warm compaction behaviors of copper powder and to optimize the warm compaction parameters, effects of lubricant concentration and compaction pressure on the green density of the copper compacts were studied. Copper compact with a green density of 8.57 g/cm3 can be obtained by compacting Cu powder with a pressure of 700 MPa at 145°C. After sintered at 1000°C under cracked ammonia atmosphere for 60 minutes, density of the sintered compact reached 8.83 g/cm3 (a relative density of 98.6%). Based on these fabrication parameters a Ti3SiC2 particulate reinforced copper matrix composite was prepared. Its density, electrical conductivity, ultimate tensile strength, elongation percentage and tribological behaviors were studied.

Biomedical Ti-24Nb-4Zr-7.9Sn Alloy Fabricated by Conventional Powder Metallurgy and Spark Plasma Sintering

2012 ◽  
Vol 520 ◽  
pp. 208-213 ◽  
Author(s):  
Shi Bo Guo ◽  
Chun Bo Cai ◽  
Yong Qiang Zhang ◽  
Yong Xiao ◽  
Xuan Hui Qu
Keyword(s):  
Tensile Strength ◽  
Powder Metallurgy ◽  
Relative Density ◽  
Spark Plasma Sintering ◽  
Raw Materials ◽  
Fracture Morphology ◽  
Sintering Process ◽  
Comprehensive Properties ◽  
Plasma Sintering ◽  
Spark Plasma

Ti-24Nb-4Zr-7.9Sn alloy was prepared by Powder Metallurgy (PM) and Spark Plasma Sintering (SPS) using titanium hydride powder, niobium powder, zirconium powder and tin powder as raw materials. The effect of sintering process on microstructure and mechanical properties was investigated by mechanical measurement and SEM. The results showed that the best sintering process by PM was at 12500C for 2 h. The relative density, tensile strength and elongation of the alloy reached 97.2%, 705MPa and 6.2%, respectively. The microstructure was a typical Widmannstatten microstructure, which possessed β-matrix and α-precipitation. The best process by SPS was at 12500C. The relative density, tensile strength and elongation of the alloy sintered by SPS reached 99.4%, 788.5MPa and 6.4%, respectively. The grain size was about 100µm and the microstructure was uniform. The fracture morphology of the alloy was ductile rupture. Compared to PM, Ti-24Nb-4Zr-7.9Sn alloy fabricated by SPS exhibited better comprehensive properties and more uniform microstructure.

scholarly journals A Mathematical Model for Predicting the Winnowing Efficiency of Bambara Groundnut Sheller

2020 ◽  
Vol 5 (2) ◽  
pp. 225-228
Author(s):  
Inimfon Samuel Ossom ◽  
Akindele Folarin Alonge ◽  
Kingsley Charles Umani ◽  
Edidiong J. Bassey
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Moisture Content ◽  
Model Equation ◽  
Model Simulation ◽  
Least Square Method ◽  
Bambara Groundnut ◽  
Least Square ◽  
Predicted Model ◽  
Experimental Values

A mathematical model for predicting the winnowing efficiency of bambara groundnut sheller was developed. The regression equation for model simulation was developed using Least Square Method. The model was verified and validated by fitting it into established experimental data from winnowing efficiency of already existed Bambara groundnut sheller. The result revealed that the fitted model correlated well with the experimental data with R-square value of 0.99. The winnowing efficiency obtained from the predicted model was approximately the same values with the experimental values. Therefore, the model equation was considered to be reasonably good for predicting the winnowing efficiency of bambara groundnut sheller for known values of moisture content and blower speed.

The Effect of Sintering Temperature to the Microstructure and Properties of AZ91 Magnesium Alloy by Powder Metallurgy

2013 ◽  
Vol 377 ◽  
pp. 250-254 ◽  
Author(s):  
Ya Jun Zhou ◽  
Ai Yun Jiang ◽  
Jian Xiu Liu
Keyword(s):  
Powder Metallurgy ◽  
Magnesium Alloy ◽  
Relative Density ◽  
Volume Diffusion ◽  
Sintering Temperature ◽  
Second Phase ◽  
Az91 Magnesium Alloy ◽  
Az91 Magnesium ◽  
Microstructure Of The Material ◽  
Energy Disperse Spectroscopy

AZ91 magnesium alloy was fabricated by powder metallurgy. The effects of sintering temperature on the relative density, hardness and tensile strength were investigated. The microstructure of the material was observed by scanning electron microscopy (SEM) and Energy Disperse Spectroscopy (EDS). The study found that the best sintering temperature is 550°C under the vacuum hotpressing, and at this sintering temperature the relative density can reach to 98.3%. SEM and EDS show that the sintering microstructure of the alloy is composed of α-Mg solid solution and the second phase β-Mg17Al12. Under the 550°C sintering temperature, Volume diffusion is the mainly sintering form, and produced more β-Mg17Al12 which is dispersively distributed on the grain boundary, and improves the hardness of alloy by second-phase strength.

Compaction of Ti-6Al-4V Powder by ECAE with Back-Pressure

2007 ◽  
Vol 29-30 ◽  
pp. 33-36 ◽  
Author(s):  
Rimma Lapovok ◽  
Dacian Tomus ◽  
Barry C. Muddle
Keyword(s):  
Powder Metallurgy ◽  
Hydrostatic Pressure ◽  
Relative Density ◽  
Shear Deformation ◽  
Vickers Hardness ◽  
Room Temperature ◽  
Low Cost ◽  
Hot Isostatic Pressing ◽  
Back Pressure ◽  
Angular Pressing

Powder metallurgy is widely used to produce alloys with low cost of production. The main drawback using powders is the level of residual porosity of final product which often implies the application of a complicated and costly hot isostatic pressing process. However, this issue can be overcome by using equal channel angular pressing (ECAE) with back pressure (BP). The use of severe shear deformation, with imposed hydrostatic pressure, allows a reduction in the range of compaction temperatures compare to those used in conventional practice. The compaction of Ti-6Al-4V powder by the ECAE method has been investigated. The compaction has been performed at temperatures starting from room temperature (RT) and increasing up to 400°C with various back pressures ranging from 0 to 350MPa. A billet processed by ECAE with 43MPa back-pressure at 400°C was found to have improved relative density of 97.5% and increased Vickers hardness of 369HV, compared to values of 96.7% and 325HV respectively obtained at RT. A relative density of 98.2% and 426HV hardness were measured for billets processed with BP = 262MPa at 400°C. A fully compact billet was obtained by applying 350 MPa of BP at 400°C.

Synthesis of High-Purity Ti3SiC2 by Infiltration-Sintering

2011 ◽  
Vol 695 ◽  
pp. 433-436
Author(s):  
Zhen Lin Lu ◽  
Qi Dan Xiao ◽  
Yong Xin Zhou ◽  
Hui Xie
Keyword(s):  
Silicon Carbide ◽  
Relative Density ◽  
High Purity ◽  
Holding Time ◽  
Sintered Compact ◽  
Titanium Silicon Carbide ◽  
Starting Mixture ◽  
Sintering Time ◽  
Titanium Silicon

Titanium silicon carbide (Ti3SiC2) is a remarkable material for its combination of the best properties of metals and ceramics. The high purity Ti3SiC2 ceramic has been prepared by infiltration sintering (IS), and the effect of a small amount of Si on Ti3SiC2 ceramic formation was investigated. The results show that the purity of Ti3SiC2 ceramic could be increased significantly and the sintering time for Ti3SiC2 could be decreased remarkably when proper amount of Si was added in the starting mixture. The Ti3SiC2 sintered compact with a purity of 99.2wt% and a relative density of 97% was obtained by the infiltration sintering from a starting mixture composed of n(Ti):n(Si):n(TiC) = 1:0.3:2 at 1500 °C with holding time of 2/3h.

scholarly journals Interpretation of the spectrum of Pb(II). Theoretical transition probabilities and lifetimes

2001 ◽  
Vol 79 (7) ◽  
pp. 999-1009 ◽  
Author(s):  
C Colón ◽  
A Alonso-Medina
Keyword(s):  
Transition Probabilities ◽  
Energy Levels ◽  
Radiative Transition ◽  
Least Square ◽  
Large Contribution ◽  
Hartree Fock ◽  
Forbidden Transition ◽  
Method Of Least Square ◽  
Experimental Values ◽  
Good Agreement

Radiative transition probabilities for 190 lines arising from the ns 2S1/2, np 2P1/2,3/2, nd 2D3/2,5/2, nf 2F5/2,7/2, and 6p2 (4P1/2,3/2,5/2, 2D3/2,5/2, 2P1/2,3/2, and 2S1/2) levels of Pb(II) have been calculated. Lifetimes of the above mentioned levels have been determined from the present transition probabilities. These values were obtained in intermediate coupling (IC) and using ab initio relativistic Hartree-Fock calculations. For the IC calculations, we use the standard method of least-square fitting of experimental energy levels by means of computer codes from Cowan. The results of calculations for radiative transition probabilities and excited states lifetimes are presented and compared with the experimental results present in the literature and with other theoretical values. There is generally good agreement between our values and the experimental data available. Analysis of the interaction shows that the level 4P5/2 of the 6s6p2 configuration presents a large contribution to the 2D5/2 level of the 6s26d configuration. This result explains the good agreement between our result and the experimental values obtained to the observed as the 6s6p2 4P5/2 – 6s 25f2F7/2 dipole-forbidden transition. PACS Nos.: 32.70^*, 32.70Fw, 32.70Cs

A Novel Forming Process for Powder Metallurgy of Superalloys

2014 ◽  
Vol 622-623 ◽  
pp. 833-839 ◽  
Author(s):  
Qian Bai ◽  
Jian Guo Lin ◽  
Gao Feng Tian ◽  
Daniel S. Balint ◽  
Jin Wen Zou
Keyword(s):  
Powder Metallurgy ◽  
Relative Density ◽  
High Performance ◽  
Low Cost ◽  
Hot Isostatic Pressing ◽  
Hot Extrusion ◽  
Forming Process ◽  
Isostatic Pressing ◽  
Wide Range ◽  
Forming Temperature

Powder metallurgy (PM) of nickel-based superalloys has been used for a wide range of products owing to their excellent special properties in processing and applications. Typical processes for high performance PM superalloys include hot isostatic pressing, hot extrusion and hot isothermal forging. Hot isostatic pressing is normally conducted at a high temperature, by using a low pressure for a long time in a closed vessel, resulting in high cost and low product efficiency. In this paper a novel forming process, i.e. direct powder forging for powder metallurgy of superalloys has been proposed. In this process, the encapsulated and vacuumed powder is heated up to the forming temperature and forged directly to the final shape, by using a high forming load for a very short time. Direct powder forging is a low-cost and energy-saving process compared to conventional PM processes, and in addition, press machines of conventional forging can be used for direct powder forming process. In direct powder forging it is important to control the relative density of the deformed part since the existence of voids could reduce the mechanical strength and fatigue life. In this paper, feasibility tests of direct powder forging are presented. Microstructure, relative density and hardness of the formed specimen were studied.

The Effect of Solid-to-Liquid Ratio and Temperature on Mechanical Properties of Kaolin Geopolymer Ceramics

2015 ◽  
Vol 660 ◽  
pp. 23-27 ◽  
Author(s):  
Romisuhani Ahmad ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Kamarudin Hussin ◽  
Andrei Victor Sandu ◽  
Mohammed Binhussain ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Flexural Strength ◽  
Relative Density ◽  
Sodium Silicate ◽  
Sintered Sample ◽  
Liquid Ratio ◽  
Naoh Solution ◽  
Sample Range ◽  
Alkaline Activator

The effect of solid-to-liquid ratio and temperature on the mechanical properties of kaolin geopolymer ceramics are studied. Kaolin and alkaline activator were mixed with the solid-to-liquid ratio in the range of 0.8-1.2. Alkaline activator was formed by mixing the 12 M NaOH solution with sodium silicate at a ratio of 0.24. Kaolin geopolymer ceramic have been produced by using powder metallurgy (PM) technique. The samples were heated at different temperature started from 900 °C until 1200 °C and the strength were tested. The relative density and flexural strength of sintered sample range approximately 84%-95% and 20-90 MPa respectively. The result revealed that the optimum flexural strength was obtained at solid-to-liquid ratio of 1.0 and the samples heated at 1200 °C achieved the highest flexural strength (90 MPa).

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