Nano/micro-bimodal powders take advantages of both nano- and micro-powders. However, densification of the bimodal powder samples is hardly predictable with conventional sintering models due to their particular shrinkage behaviors. In this study, sintering behaviors of micro-, nano- and nano/micro-bimodal powders were investigated, and a two-stage master sintering curve model was developed. Micro-, nano- and three bimodal powder samples were prepared via powder injection molding process. The samples were sintered using a dilatometer to analyze the densification behavior, and microstructures of the samples with various sintering temperatures were observed. The results demonstrated the sintering mechanism of the bimodal and nano-powder samples could be divided into two stages. Based on observation, the two-stage master sintering curve model was suggested by introducing transition temperature, and sintering activation energy and material parameters were obtained for each region from the dilatometric data. The two-stage master sintering curve model was successfully developed with high accuracy. The model significantly reduced the maximum error of prediction density from 6 to 0.8%. The result indicated the two-stage master sintering curve model could describe the sintering behaviors of the bimodal and nano-powder samples. (C) 2019 Elsevier B.V. All rights reserved.