Novel Sintering Processes and News in Conventional Sintering and Grain Growth: Field Assisted Sintering IV (SPS & Microwave)
Program Organizers: Ricardo H. R. Castro, University of California at Davis; Olivia Graeve, Alfred University; Klaus van Benthem, University of California at Davis
Thursday 8:00 AM
October 11, 2012
Room: Room 306
Location: David L. Lawrence Convention Ctr
Session Chair: Jorgen Rufner, University of California - Davis
8:00 AM
Consolidation and Devitrification Behavior of Iron-Based Amorphous Alloys for Ballistic Applications: Michael Saterlie1; Paulo Colmenares1; Olivia Graeve1; 1Alfred University
New iron-based amorphous alloys have been found to exhibit enhanced corrosion resistance and strength. In this study, one such amorphous alloy (Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4) has been chosen for its emerging properties in ballistic projectiles and armor plating, kinetic energy weapons, and micrometeoroid protection of space assets. Typically, bulk amorphous alloys exhibit high strengths, but lack toughness, which is crucial for use in projectiles. One solution to this problem is the addition of nanoparticles. We will present the incorporation of tungsten and/or tantalum nanoparticles into our amorphous alloys with two purposes in mind: (1) the addition of the reinforcement phase that can hinder the propagation of shear bands, thus enhancing the toughness, and (2) the increase in specific density of the material, which augments the penetration while retaining their structural robustness under ballistic impact. The consolidation and divitrification of the materials using spark plasma sintering will be analyzed.
8:20 AM Invited
Field Assisted Sintering of Refractory Metals for High-Strain Rate Applications: Chris Haines1; 1US Army ARDEC
Field-Assisted Sintering Technology (FAST) has been employed to consolidate refractory metals (e.g. W, Ta) as a part of a powder metallurgy approach to obtaining materials for use in high-strain rate applications. FAST affords the ability to process these high-melting point, relatively hard-to-sinter materials in an expedient manner due to the simultaneous application of high pressure and rapid, volumetric heating. The sintering behavior of these materials will be discussed with particular focus on the effect of oxygen content in the starting powders. XRD, SEM, and mechanical properties of the sintered materials will be reported.
8:40 AM
Spark Plasma Sintering of As-Received and As-Cryomilled Tungsten Powder: Lin Huang1; Yuhong Xiong2; Chris Haines3; Ryan Carpenter3; Darold Martin3; Deepak Kapoor3; Enrique Lavernia1; Julie Schoenung1; 1University of California, Davis; 2University of Minnesota; 3U.S. Army, Armament, Research, Development and Engineering Center (ARDEC)
Tungsten, a promising material for structural applications due to its combination of superior properties, is limited in actual use because tungsten is normally brittle at room temperature. Tungsten exhibits a brittle-to-ductile transition at elevated temperatures, although the exact transition temperature is dependent on various microstructural parameters. The influence of grain size, however, has not been well studied. To evaluate the effect of grain size reduction into the nanometer regime, two starting powders are compared: as-received submicron powder and cryomilled powder. Spark plasma sintering is used to consolidate the pure tungsten powders. Pressures as high as 200 MPa and low sintering temperatures hinder grain growth while enhancing densification during sintering. The kinetics of densification and grain growth are evaluated through shrinkage comparisons and microstructure evolution using SEM and TEM. Vickers hardness, nanoindentation and nanoscratch tests are conducted to study the effect of grain size on the corresponding induced deformation.
9:00 AM
Spark Plasma Sintering: Processing of Nuclear Materials: Robert O'Brien1; Nathan Jerred1; 1Center for Space Nuclear Research, Idaho National Laboratory
Spark Plasma Sintering (SPS) is a powder sintering process that has many advantages over traditional sintering methods such as Hot Isostatic Pressing and Hot Pressing. Specifically, SPS has the capability to process ceramics and metallic materials at significantly reduced temperatures and over greatly reduced time. Thus, SPS is particularly attractive to the processing of nuclear ceramics, claddings and cermets into sintered net-shaped compacts for fuels applications. The development of a dedicated SPS processing facility with integrated radiological materials handling capacity is presented. Additionally, example applications of SPS to nuclear fuel and waste form fabrication are presented. These include the demonstrated encapsulation of 50 vol.% 3 μm depleted uranium dioxide powder within a tungsten super alloy matrix produced from sub-micron tungsten powders.
9:20 AM Invited
Spark Plasma Sintering of Fe-Based Amorphous Metal / Y2O3 Ceramic Composites: Raghunath Kanakala1; Michael Saterlie2; Daniel Davies2; Sarai Escalante2; Sebastian Diaz de la Torre3; Olivia Graeve2; 1University of Idaho; 2Alfred University; 3Instituto Politecnico Nacional
Metallic glasses are amorphous alloys that contain atoms of significantly different sizes, leading to low free volume and higher viscosities than typical metals and alloys in the molten state. The viscosity prevents the atoms from diffusing in order to form an ordered lattice, resulting in low shrinkage during cooling and resistance to plastic deformation. The absence of grain boundaries, which are usually considered areas of weakness, leads to better resistance to wear and corrosion of these materials. We present the spark plasma sintering and crystallization behavior of two Fe-based amorphous metals with incorporation of yttria nanoparticles. The two compositions of interest are Fe48Mo14Cr15Y2C15B6 and Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The kinetics of divitrification in these two materials has been carefully analyzed using X-ray diffraction, including determination of the predominant phases in the devitrified samples. These results have been correlated to the sintering parameters, including sintering temperature, time, hold time, and pressure.
10:00 AM Break
10:20 AM
Carbon Nanotube/Bioglass Composites for Bone Graft Support: Jing Zhang1; Zhizhong Jia2; Chengchang Jia2; 1Indiana University - Purdue University Indianapolis; 2University of Science and Technology Beijing
Novel carbon nanotube reinforced 45S5 bioglass composite materials have been successfully synthesized using mechanical mixing followed by spark plasma sintering (SPS) technique. The novel carbon nanotube reinforced bioglass composites showed substantially improved mechanical properties. Compared with the bioglass matrix, the maximum flexural strength and fracture toughness increased 159 % and 105 %, respectively. Enhanced strength and toughness mechanisms are attributed to the interfacial bonding and bridging effects between the carbon nanotubes and the bioglass powders during crack propagations. The results suggest that the composite is a promising material for bone graft support.
10:40 AM Invited
A Study of Neck Growth Kinetics between Al Alloy Flake Powders during SPS Processing: Mathieu Brochu1; Bamidele Akinrinlola1; Raynald Gauvin1; 1McGill University
Typical sintering studies focus on sphere-sphere/sphere-plate conditions to study neck growth between sintering particles. In most cases, conventional furnaces are used; the growth is solely associated with the interface characteristics and the sintering cycle conditions. The study of neck growth in pressure-assisted processes is complex, and made further difficult when current is part of the process, such as in SPS processing. In this study we present an investigation of the neck growth between flat (i.e.: low curvature) flake powders as a function of various SPS processing parameters, such as temperature, time, pressure and applied current. Al alloys 5083 and 5356 were used and a cryomilling process was used to fabricate the flattened powders. The flake morphology was used in order to identify and analyze the neck growth kinetics. Effective diffusion coefficient and activation energy were calculated to elucidate the influence of the applied current on the sintering kinetics and mechanisms.
11:20 AM
The Effect of Coke Particle Size on Thermal Profile of Sintering Process Product: Nader Tahanpesarandezfuly1; Ali Heidari Moghadam1; 1Department of Metallurgy, Dezfool branch, Islamic Azad University, Dezfool- Iran
In this research, the effect of coke particle size on thermal profile in the production process is investigated in the laboratory environment. Baking process and sinter production was performed for different ranges of coke particle size while other parameter like, iron ore, lime and sintering mixture particle sizes, suction conditions and so on were kept constant. Thermal profile was achieved by measuring the temperature in different places of sintering bed. Investigating the thermal profile in different tests confirmed that coke grain size has a significant effect on thermal profile. The effect of coke particle size on coke combustion velocity, maximum temperature, the amount of produced melting phase as well as the flame front speed was understood by analyzing the achieved profiles and consequently the optimal grain size was known. The coke suitable particles size could have a great effect on quality of the produced sinter.