Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xvi, 140 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 137-140).

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This dissertation analyzes archaeological features and materials related to metal production excavated from the early colonial component (1598-1680 AD) of the Pueblo of Paa-ko (LA 162), Bernalillo County, New Mexico. The dissertation characterizes the metallurgical technology employed at Paa-ko through the integration of archaeological, technological and ethnohistorical data in order to develop a comprehensive understanding of the technology in terms of its material and social aspects. By integrating many scales of analysis, from site specific behavioral observations, to regional and global economic networks, the project investigates how economic, technical and social knowledge is communicated, contested, and transformed across the social and cultural boundaries present in early colonial communities. The dissertation addresses how the situated agency of indigenous practitioners incorporated within colonial industries, shapes such industries. It also explores the effects of such agency in the resulting technology at LA 162, and early Spanish colonial constructions of 'value' (of both an economic and social nature), more broadly.

The implementation of technologies such as aluminum powder metallurgy (P/M) can be used in the automobile industry to have potential economic and environmental advantages. This technology to produce vehicle components can offer the combination of weight savings due to the low density of aluminum and material and machining savings via near net shape processing attributes. In an effort to expand the scope of application for aluminum P/M, considerable research has emphasized the development of new alloys and composites. One such alloy is P/M 2324, an aluminum-copper-magnesium alloy developed to have increased mechanical properties over the standard aluminum P/M alloys of the AC2014 type. The objective of this work was to undertake a comprehensive study on the effects of hot deformation on the emerging alloy P/M 2324 as well as the alloy with a SiC addition. Here, a forgeability study of these alloys and its wrought counterpart AA2024 was completed. To

A new finite element model was developed to predict the density distribution in an Alumix 321 powder metallurgy compact. The model can predict the density distribution results of single-action compaction from 100 to 500 MPa compaction pressure. The model can also determine the amount of springback experienced by a compact upon ejection from the die at 100 and 300 MPa compaction pressure. An optical densitometry method, along with the creation of a compaction curve, was used to experimentally predict density distributions found within compacts, and found results that were consistent with both literature and finite element simulation. Further powder characterization included testing apparent density and flow rate of the powder. A literature review was also conducted and the results of which have been organized by three categories (powder type, material model, and finite element code) for easy reference by future powder researchers.

Nickel-based Superalloys are widely used in the steam turbine power generation and aerospace industries. They possess the desirable qualities of high-temperature strength, oxidation and corrosion resistance and can operate in some of the highest temperature ranges of the structural metals. The oxidation resistance of a Superalloy is achieved primarily through the formation of a dense alumina and/or chromia oxide layer(s) including spinels. This resistance has been further improved in wrought and cast alloys through the addition of reactive elements such as silicon, yttrium and lanthanum, although the exact effects of these elements have not been well defined. This project concentrated on a powder metallurgy ternary master alloy consisting of Ni-12Cr-9Fe (w/o) with additions of 6w/o aluminum, 0.5w/o Si, and 0.1w/o Y, in various combinations. Specifically, the primary goal was to produce and characterize a PM manufactured nickel-based Superalloy with minor additions of reactive elements and to assess the effectiveness of the Si and/or Y in improving the oxidation resistance. JMatPro modeling software was first used to help determine temperatures at which various events would occur in the alloys such as solutionizing and liquation temperatures. Subsequently green compacts were produced by a press (uni-axially) and sinter route to create transverse rupture strength bars (TRS bars). These bars were then thermomechanically deformed using a Gleeble tester to reduce porosity followed by a heat treatment to restore a microstructure better suited for high temperature oxidation. Sectioned TRS bars were then oxidized (static) 900?C in air for times up to 1000h and the influence of the Si/Y additions on oxidation resistance was determined via a combination of weight gain data and microstructural examination. Whereas JMatPro predicted solutionizing temperature of the compositions studied (1010°C quaternary; 1020°C quaternary + Si, respectively) these values were slightly lower than the results observed through DSC experiments (1045°C quaternary; 1065°C quaternary + Si, respectively). A w/o ?’ of approximately 25% was predicted by the modeling tool, but values of 58.3% to 61.7% were determined using a point count method. Finally, the addition of 0.5w/o Si to the quaternary Ni-Cr-Fe-Al PM system provided a measureable improvement in the oxidation resistance both in terms of thickness of oxide layer and in overall weight gain. Conversely, 0.1w/o Y provided little benefit, and was shown to be detrimental to alloys not containing Si.

The objective of this research was to design aluminum powder metallurgy (PM) alloys and processing strategies that yielded sintered products with thermal properties that rivaled those of the cast and wrought aluminum alloys traditionally employed in heat sink manufacture. Research has emphasized PM alloys within the Al-Mg-Sn system. In one sub-theme of research the general processing response of each PM alloy was investigated through a combination of sintering trials, sintered density measurements, and microstructural assessments. In a second, the thermal properties of sintered products were studied. Thermal conductivity was first determined using a calculated approach through discrete measurements of specific heat capacity, thermal diffusivity and density and subsequently verified using a transient plane source technique on larger specimens. Experimental PM alloys achieved >99% theoretical density and exhibited thermal conductivity that ranged from 179 Wm-1K-1 to 225 Wm-1K-1. Thermal performance was largely dominated by the amount of magnesium present within the aluminum grains and in turn, bulk alloy chemistry. Data confirmed that the novel PM alloys were highly competitive with even the most advanced heat sink materials such as wrought 6063 and 6061. Two methods of thermal analysis were employed in order to determine the thermal conductivity of each alloy. This first consisted of individual analysis of the specific heat capacity (Cp), thermal diffusivity (?) and density (?) as a function of temperature for each alloy. The thermal conductivity (K) was subsequently determined through the relationship: K=C_p ??. The second means of thermal analysis was a direct thermal conductivity measure using a transient plane source (TPS). The thermal diffusivity and density of samples were both found to decrease with temperature in a linear fashion. Conversely, the specific heat capacity was found to increase with temperature. The only measured thermal property that appeared to be influenced by the alloy chemistry was the thermal diffusivity (and subsequently the calculated thermal conductivity). Both means of thermal analysis showed high thermal conductivity in alloys with low concentrations of magnesium, demonstrating the significance of having alloying elements in solid solution with aluminum. Overall, several alloys were developed using a press and sinter approach that produced higher levels of thermal conductivity than conventional aluminum heat sink materials. The highest thermal conductivity was achieved by alloy Al-0.6Mg-1.5Sn with a calculated value of 225.4 Wm-1K-1. This novel aluminum PM alloy was found to exceed both wrought 6061 and 6063 (195 and 217 Wm-1K-1 respectively). Furthermore, PM alloy Al-0.6Mg-1.5Sn was found to have a significant advantage over die-cast A390 (142 Wm-1K-1).

Extensive computer predictions have been carried out by the author to study flow, addition dispersion and particle motion during central gas injection into cylindrical vessels. In conjunction with numerical computations, experiments were conducted in a 0.30 scale water model of a 150 ton steel processing ladle, using a Froude number scaling criterion. Two typical gas injection configurations (i.e., conventional central injection and C.A.S. alloy addition procedure) were investigated. / Flow visualization studies were carried out using a suspended network of silken threads, mean velocity vectors and overall flow patterns were determined by video recording techniques, while mean velocity vectors and associated turbulence level were also measured with laser doppler velocimetry. These measurements show very reasonable agreement with equivalent numerical predictions. / To simulate the subsurface motion of additions, spherical wooden balls of various densities were dropped from typical heights, and their subsurface trajectories, immersion times, etc., recorded by means of a video recorder. Frame by frame analysis of the video tapes showed trends which are in good accord with computed trajectories. / Mixing times of simulated molten additions were measured by the conductivity measurement technique. These were compared with prediction from an equivalent tracer dispersion model and excellent agreement achieved. / For industrial application, flow, particle motion, and mixing times in a 150 ton steel processing ladle have been predicted and their technological significance discussed.