DENSIFICATION AND SHAPE RETENTION IN SUPERSOLIDUS LIQUID PHASE SINTERING

摘要

Rapid sintering densification of relatively large prealloyed powders is possible by exceeding the solidus temperature in an approach termed supersolidus liquid phase sintering. This process is often limited by a narrow processing window for attaining densification without distortion. Densification and distortion both reflect viscous flow responses of the solid-liquid mixtures. In the present research, a control micro- structure softening parameterζ, which combines the effects of grain size, liquid volume fraction, and conti- guity, is proposed to separate densification and distortion events. This microstructure parameter has two critical values,ζ _densif and ζ_distort, for densification and shape loss, respectively. It must be smaller than ζ_distort to avoid shape distortion. while for densification, it must be larger than ζ _densif. As ζ_densif is smaller than ζ_distort, there is window of sintering conditions where densification is achieved without accompanying shape loss. Understanding this parameter provides a means to design alloys and processing cycles for net shape, full density components by supersolidus liquid phase sintering.