Thesis (Ph. D.)--University of Wisconsin--Madison, 1976. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 145-149).

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 66.

Thesis (Ph. D. in materials science)--Washington State University, May 2007. / Includes bibliographical references.

This work presents an investigation into two areas : the development of zinc based brazing alloys for the joining of copper produced by the rapid solidification technique; the study of the development of microstructures in rapidly solidified dilute zinc alloys. A new model has been proposed, based on the present experimental results and the available data from the literature, to account for the ribbon formation mechanism. Within this model ribbon formation in melt spinning is mainly determined by the behaviour of the viscosity in undercooled melts. It has been shown that, contrary to previous studies, the present model can be used to predict the ribbon thickness of both crystalline and amorphous alloys, and the agreement with the measured values is excellent. The development of microstructures in dilute zinc alloys during rapid solidification has been studied by the deliberate addition of impurity elements. Significant differences in structures are observed between the dilute zinc alloys and high purity zinc. The high purity zinc exhibits a strong preferred orientation with the basal plane parallel to the ribbon surface. The severity of this texture markedly reduces with the formation of cellular substructures in dilute zinc alloys. The morphology of the cells depends on the type of impurity elements present. The presence of impurity elements which expand on solidification leads to the development of an eutectic-like structure consisting of regular lamellae. This requires reorientation of the basal plane and instability of the solid liquid interface during solidification. The instability conditions of the planar solid liquid interface during rapid solidification of these alloys have been examined by using the morphological stability criterion. A possible mechanism which accounts for the formation of unusual structures observed in rapidly solidified dilute zinc alloys has been proposed. The observed variety of microstructures of binary Zn-Mg alloys, and the structural transitions across the ribbon thickness have been reported. Comparisons are made between as-cast and rapidly solidified materials and the resulting structures have been described using a growth rate composition map. Rapidly solidified eutectic and hypereutectic alloys show a tendency to form an amorphous phase. A total of more than 50 zinc based alloys have been investigated for the development of brazing filler metal. Alloys have been examined, and their compositions optimized, in terms of their spreading and wetting abilities and brazing performances to obtain a suitable candidate. Based on the experimental results it has been suggested that Zn-Mg alloys could be used for the joining of copper. They exhibit a lower surface tension, a lower density and comparable mechanical properties to high temperature high strength silver based brazing alloys.

If an expensive part such a turbine blade or high quality tool needed to be refurbished instead of discarded, the part would have be coated in a way that would resemble or even exceed its previous surface properties. In this regard, this work studies a tungsten carbide-nickel braze alloy hardface composite prepared by liquid infiltration. A unique polymeric binder system was used to form the brazing cloth which formed the carrier for the tungsten carbide and nickel braze alloy particles. After thermal pyrolysis of the binder, the nickel braze alloy would infiltrate into a porous tungsten carbide layer becoming a hard surface coating or hardfacing. These brazing cloths were formulated to achieve a theoretical full density coating after the infiltration process. The hardface would also be brazed to its base substrate. In this study, infiltration of a porous material and brazing are mated in one continuous process. The goal of this research is the measure of hardfacing in relations to powder-polymer processing, infiltration of porous materials and brazing cycles to achieve superior hardness and braze interface quality.

Graduation date: 1994

[by] C.S. Pearsall [and] P.K. Zingeser. / Bibliography: p. 10. / Army Signal Corps Contract no. W36-039-sc-32037, Project no. 102B. Dept. of the Army Project no. 3-99-10-022.

In order to evaluate the feasibility of forming Pure Mg – Pure Mg and Mg Alloy – Mg Alloy joints using soldering and brazing, four filler metals (Sn, Sn-9Zn, Sn-9Zn+X wt%Mg and Mg:Zn:X(Sn-9Zn)) were used at peak heating temperatures of ~250°C, 350°C and 450°C. Differential Scanning Calorimetry (DSC) and microstructure characterization were used to evaluate the successful joints. When using Sn as a filler metal, a joint forms, at temperatures as low as 235°C, which consists of a Mg-Sn eutectic filler layer and a continuous Mg2Sn intermetallic layer at the filler metal/Mg interface. This joint microstructure persists up to peak temperatures of 350°C and 450°C. The main effect of increasing the peak temperature causes an increase in the thickness of the Mg2Sn layer. Joints formed using Sn-9Zn prealloyed filler metal, developed a filler metal composition according to a Sn rich Mg-Sn-Zn ternary microstructure. A continuous Mg2Sn layer still formed in the joint. Ternary phase diagram predictions support the development of a number of MgxZny intermetallic compounds. However, only isolated experimental evidence of Mg-Zn liquid formation was present at peak heating temperature of 350°C and no evidence of MgxZny intermetallic layers was observed for both base metal systems using Sn-9Zn filler metal at 250°C and 350°C. Upon further heating above 350°C, a Mg7Zn3 layer forms which eventually leads to a Mg-Zn eutectic liquid formation as 450°C is reached. Wide gap Transient Liquid Phase Bonding (TLPB) was carried out by adding Mg to Sn-9Zn filler metal. Decrease in liquid volume fraction during solidification was noted with increase in Mg wt% as well as an increase in heating temperatures. Complete consumption of the filler metal was observed at 30wt% Mg and 450°C. Microstructural events were noted to be similar to Mg-Mg couples using Sn-9Zn filler metal. Mg-Zn, 50:50 wt% filler metal was thus used to evaluate joints without Mg2Sn intermetallic formation. Mg-Zn binary liquid phase formation was found to correspond to 342°C upon initial heating and presence of solid Mg7Zn3 in microstructure was found in samples heated to 350°C. Increase in diffusional solidification of Zn into the unreacted Mg powder and Mg base metal was noticed upon further heating to 450°C. Significant influence on the microstructure was noticed with addition of prealloyed Sn-9Zn powder to Mg-Zn filler metal mixture. Sn-9Zn was observed to be consumed in solid state during initial heating while alloying and dissolution of Pure Mg particles was seen to be accelerated. All Pure Mg powder was consumed indicating a large volume fraction present at 450°C in the case of filler containing 10% Sn-9Zn. The primary cellular grains of (Mg) grow from the Mg base metal substrate and Mg7Zn3 solidifies in the intercellular region. In the original filler metal portion of the diffusion couple, a mixture of (Mg), Mg7Zn3 and eutectic appears with a more dispersed character indicative of an equiaxed growth process. Promising results from 45Mg:45Zn:10(Sn-9Zn) wt% and peak heating temperature of 450°C could form basis for future work which can eventually lead to a commercial application.

The work explains how the dynamics of the release of water vapors from flux during the Control Atmosphere Brazing influences the process conditions important for the quality of the brazed product. The process involves sequential events such as continuous ramp-up heating, flux and filler melting, reactive flow, isothermal dwell and rapid quench solidification performed under the controlled atmosphere. During this complex process effluents are released. Some effluents are detrimental for the product quality (water vapor) and some are harmful for the environment (HF). We selected to study water vapor emissions with an objective to quantify these emissions and to consider their influence on the manufacturing process. Experiments were conducted using different fluxes. Findings are presented to compare the vapors released in each case. The objective is not necessarily to develop a metric for sustainability, but to understand the kinetics of an effluent release. A simple predictive model has been devised to approximate experimental data behavior. The data from the TGA analysis obtained from other sources, and the dew point temperature history from the controlled atmosphere brazing experiments performed in course of this work, have been used for the purpose of comparison and analysis.

In order to evaluate the feasibility of forming Pure Mg – Pure Mg and Mg Alloy – Mg Alloy joints using soldering and brazing, four filler metals (Sn, Sn-9Zn, Sn-9Zn+X wt%Mg and Mg:Zn:X(Sn-9Zn)) were used at peak heating temperatures of ~250°C, 350°C and 450°C. Differential Scanning Calorimetry (DSC) and microstructure characterization were used to evaluate the successful joints. When using Sn as a filler metal, a joint forms, at temperatures as low as 235°C, which consists of a Mg-Sn eutectic filler layer and a continuous Mg2Sn intermetallic layer at the filler metal/Mg interface. This joint microstructure persists up to peak temperatures of 350°C and 450°C. The main effect of increasing the peak temperature causes an increase in the thickness of the Mg2Sn layer. Joints formed using Sn-9Zn prealloyed filler metal, developed a filler metal composition according to a Sn rich Mg-Sn-Zn ternary microstructure. A continuous Mg2Sn layer still formed in the joint. Ternary phase diagram predictions support the development of a number of MgxZny intermetallic compounds. However, only isolated experimental evidence of Mg-Zn liquid formation was present at peak heating temperature of 350°C and no evidence of MgxZny intermetallic layers was observed for both base metal systems using Sn-9Zn filler metal at 250°C and 350°C. Upon further heating above 350°C, a Mg7Zn3 layer forms which eventually leads to a Mg-Zn eutectic liquid formation as 450°C is reached. Wide gap Transient Liquid Phase Bonding (TLPB) was carried out by adding Mg to Sn-9Zn filler metal. Decrease in liquid volume fraction during solidification was noted with increase in Mg wt% as well as an increase in heating temperatures. Complete consumption of the filler metal was observed at 30wt% Mg and 450°C. Microstructural events were noted to be similar to Mg-Mg couples using Sn-9Zn filler metal. Mg-Zn, 50:50 wt% filler metal was thus used to evaluate joints without Mg2Sn intermetallic formation. Mg-Zn binary liquid phase formation was found to correspond to 342°C upon initial heating and presence of solid Mg7Zn3 in microstructure was found in samples heated to 350°C. Increase in diffusional solidification of Zn into the unreacted Mg powder and Mg base metal was noticed upon further heating to 450°C. Significant influence on the microstructure was noticed with addition of prealloyed Sn-9Zn powder to Mg-Zn filler metal mixture. Sn-9Zn was observed to be consumed in solid state during initial heating while alloying and dissolution of Pure Mg particles was seen to be accelerated. All Pure Mg powder was consumed indicating a large volume fraction present at 450°C in the case of filler containing 10% Sn-9Zn. The primary cellular grains of (Mg) grow from the Mg base metal substrate and Mg7Zn3 solidifies in the intercellular region. In the original filler metal portion of the diffusion couple, a mixture of (Mg), Mg7Zn3 and eutectic appears with a more dispersed character indicative of an equiaxed growth process. Promising results from 45Mg:45Zn:10(Sn-9Zn) wt% and peak heating temperature of 450°C could form basis for future work which can eventually lead to a commercial application.