Strength Evolution in the Sintering of Bronze Powder Metal Compacts and Application to Thermal Cycle Design
Abstract
Powder metallurgy allows fabrication of complex net-shape components. Accurate design specification of these components requires precise prediction of their response to sintering process parameters. Nonuniform sintering responses, such as strain gradients, can result in process failures such as distortion and cracking. To avoid these types of process failures without costly trial and error design, the most important response to understand is the compact's strength as it evolves during the sintering process. A unique device and method have been developed to measure the in situ strength as a function of sintering process parameters. The specific strength parameter investigated and modeled in this work was transverse rupture. This strength was precisely determined for 90Cu-10wt.%Cu prealloyed powder bronze compacts in response to sintering time, temperature and heating rate. At a sintering temperature of approximately 350 deg C the green strength of 10 MPa decreased 50% due to the annealing of the cold worked strength afforded during compaction At higher temperatures, a dramatic increase in strength (dependent also on time and heating rate) due to sintering was observed. As the compact was processed beyond approximately 600 deg C, thermal softening dominated sintering strengthening to cause an overall degradation in strength with respect to temperature. This first ever data made possible a model to predict the in situ evolution of strength during sintering. The consequence of this work is to identify the thermal cycles that maximize strength, thereby minimizing distortion and otherwise improving dimensional tolerances.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 15, 1998
- Accession Number
- ADA344923
Entities
People
- Gregory A. Shoales
Organizations
- Pennsylvania State University