This research continues the earlier researches on wear friction and lubrication and its application to the powder metallurgy industries. A detailed study of the parameters involved in wear and friction has been made by using the "Pin and Disc" machine with cross cylinders technique. One iron powder was chosen and compacted over a range of densities with a series of metallic stearates as admixed lubricants for the purpose of examinations. These compacts were used as the "pins" for the wear and friction apparatus, the "disc" was made from high carbon high chromium steel which is one of the steels normally used in punches and dies in the powder metallurgy industries. The wear behaviour of these compacts was studied in relation to the following parameters: applied load between compact (or pin) and disc, sliding speed, travelled distance, density and hardness of compact. These were examined for a range of stearate lubricants and the wear rates determined, these data were then related to the possible industrial life for punches and dies in powder metallurgy presses. Besides wear rate, friction forces between the compact (or pin) and disc were measured and these forces of friction were translated into coefficients of friction for each type of lubricant. The thesis presents the results of these investigations with a survey of current theories on wear and friction of metallic systems relevant to powder metallurgy. Conclusions have been drawn and suggestions made on the most useful solid lubricant necessary in the pressing of metallic powders to reduce wear and friction in production presses. Calculations have been carried out using the data collected to estimate the possible press tool wear and accordingly a possible tool life was determined for pressing with each type of ~tearate lubricant. The overall conclusion was that zinc stearate is the best solid lubricant in the five metallic stearates (Al, Na, Mg, Ca and Zn) for use in iron powder compaction.

The current, commercially available, press and sinter Al-Mg-Si-Cu alloys are based on wrought or cast alloy compositions and have not been tailored for the press and sinter process. The limited development of the Al-Mg-Si-Cu alloys for the press and sinter process can be partly attributed to a poor understanding of the effects of processing conditions on the sintering behaviour. The primary objective of this work was to investigate and understand the effects of processing conditions on the sintering behaviour of Al-Mg-Si-Cu-(Sn) alloys. Dilatometry was used in conjunction with other experimental techniques to elucidate and understand the expansion and shrinkage events that occur during the liquid-phase sintering of Al-Mg-Si-Cu-(Sn) powder metallurgy alloys. Samples were uni-axially pressed from elemental metal powder blends, de-waxed, and then sintered in a horizontal push-rod dilatometer to record the dimensional changes in the pressing direction. The processing conditions examined included the alloy composition, temperature, green density and atmosphere. A liquid forms during heating due to reactions between the alloying elements and the aluminium. This liquid is initially non-wetting on the oxide layer of the aluminium particles, resulting in separation of the particles, which is manifested by expansion of the sample. The oxide is reduced as sintering progresses, alleviating the non-wetting conditions. When more liquid forms, further expansion occurs, despite the improved wetting conditions. It is proposed that atmospheric oxygen and/or nitrogen can react with the liquid, forming a solid phase (‘shell’) at the liquid-vapour interfaces. These shells prevent the liquid from wetting the particles, resulting in further expansion and preventing shrinkage. Unbalanced diffusivities (the Kirkendall effect) between the aluminium and silicon contribute to the expansion. A mechanism is proposed to account for the transition to shrinkage, whereby the shells at the liquid-vapour interface rupture when there is a rapid increase in the volume of contained liquid. The liquid then flows out and over the shells, onto the aluminium substrate, causing shrinkage. Magnesium and nitrogen delay the transition to shrinkage by facilitating nitride shell formation at the solid-liquid interface. Silicon and tin cause an earlier transition to shrinkage by increasing the liquid volume. In addition, tin promotes shrinkage by segregating to the liquid-vapour interfaces, limiting the thickness of the shells at the liquid-vapour interfaces. The two dominant liquid-phase shrinkage mechanisms during the sintering of Al-Mg-Si-Cu-(Sn) alloys are rearrangement and pore-filling. Contact-flattening is not a dominant shrinkage mechanism, but may occur concurrently with the other mechanisms. If contact flattening occurs, a decrease in the pressure of isolated pores increases the total shrinkage rate. Nitrogen increases the shrinkage rate during rearrangement by restricting grain-growth. Magnesium increases the shrinkage rate during rearrangement by reducing the solid-liquid interface energy. Magnesium and nitrogen are essential for the formation of nitride within isolated pores, which decreases the pore pressure and increases the contribution of contact-flattening on the total shrinkage rate. Silicon reduces the beneficial influence of magnesium during rearrangement by diluting the magnesium content in the liquid. Silicon increases the pore-filling rate due to an increase in the liquid volume. Magnesium increases the pore-filling rate by facilitating aluminium nitride formation within isolated pores and by increasing the pore-filling. Tin additions can decrease the pore-filling rate due to its segregation to the liquid-vapour interface, limiting the consumption of nitrogen within isolated pores.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1910. / The entire thesis text is included in file. Typescript. Illustrated by author. Bachelor of Science degree in Mining Engineering determined from "1874-1999 MSM-UMR Alumni Directory". Title from title screen of thesis/dissertation PDF file (viewed March 19, 2009)

Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: Heat Treatment; Powder Metallurgy; Phase Transformations; Finite Element Modeling Includes bibliographical references.

Techn. Univ., Diss.--Freiberg (Sachsen), 2001.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Zugl.: Freiberg, Techn. Univ. Bergakad., Diss., 2001.

Thesis (Master's)--Technion - Israel Institute of Technology, Faculty of Agricultural Engineering, 1967.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1985. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 289-299).