Evolution of Microtexture and Microstructure During Sintering of Copper
- PDF / 4,661,948 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 61 Downloads / 238 Views
SOLID state sintering is one of the most important processing routes for producing different shaped objects including the one with near net shape design from metals and alloys as well as ceramics. In early studies of solid state sintering, the mechanism of sintering was considered as the viscous flow process,[1–3] while later studies established atomic diffusion as the mechanism of sintering. One such example is found in the work of Dedrick and Gerds,[4] where a study on neck growth during copper sintering of large particle size powder ranging from 560 to 640 lm showed that experimental results were comparable with the volume diffusion model, which is associated with low surface and grain boundary area. The extracted diffusion data agreed with the experimental data. Also, in 1949, Alexander and Balluffi investigated the role of grain boundary for pore annihilation.[5] This work gave insight to include grain boundary diffusion and grain growth in sintering models. There was development of sound theory for G.N. FELEGE, N.P. GURAO, and ANISH UPADHYAYA are with the Department of Materials Science & Engineering, Indian Institute of Technology Kanpur, Kanpur, UP, 208016, India. Contact e-mail: [email protected] Manuscript submitted October 14, 2018. Article published online June 18, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
sintering due to the agreement between the experimentally found sintering rates with atomic diffusion models. In 1974, Ashby[6] reported sintering diagrams that were constructed by numerical computation to identify the dominant sintering mechanism for a given temperature and neck size. He used the theoretical model of sintering to construct the diagrams. Neck growth between spherical particles is modeled considering diffusion as the main mechanism of mass transport during sintering. During the process of sintering, neck forms between the powder particles and density increases. This process involves diffusive transport of matter for neck growth as well as for densification. The sintering diagram is constructed on a two-dimensional space with neck size and temperature as coordinates. Ashby constructed the diagram first by identifying the dominant mechanism that contributes more to the neck growth rate than any other single mechanism; then, the boundaries of these fields are obtained by equating pairs of rate equations and solving for neck size as a function of temperature. At the field boundaries, two mechanisms contribute equally to the sintering rate. On the diagram, there are also contour lines that represent constant neck growth rate or constant time lines superimposed.
VOLUME 50A, SEPTEMBER 2019—4193
Solid state sintering involves densification of the powder compact in solid state through three overlapping stages.[7] The initial stage is characterized by the formation of neck between particles and its contribution to compact shrinkage is limited. During intermediate stage pore rounding, densification and grain growth take place and considerable densification occurs before isolation of pores. At the final st
Data Loading...
