中文摘要：

选用球型雾化铁粉为典型材料,在温度1 075℃、压力40 MPa、保温时间5 min和脉冲8：2的条件下,以不同升温速率（10,30,50,70和90 K/min）进行放电等离子烧结,对烧结体的致密度、微观组织以及致密化动力学等进行分析,研究升温速率对SPS铁粉致密化的影响。结果表明：粉末的SPS致密化过程与传统热压类似,烧结初期致密化速率较大;然后随温度升高,致密化速率加快;烧结后期致密度大幅提高,但由扩散蠕变控制的致密化过程受到晶粒长大的影响,最终致密度趋于稳定。由于保温时间较短,材料的致密度随升温速率提高而减小。提高升温速率能有效抑制样品与模具接触而发生的渗碳行为。

英文摘要：

The effects of heating rate on densification process of metal powders were investigated by using atomized iron powders as raw material. The heating rate was ranged from 10 K/rain to 90 K/min. During the SPS process, the samples were sintered for 5 min under the condition of 1075 ℃ and 40 MPa. Then the density, microstructure and densification kinetics of polished samples were observed and analyzed. The results show that the densification process of SPS is similar to that of heating pressing process. In the initial stage of sintering, the densification rate of powders is relatively high, and then the sintered sample obtains a high relative density with increasing the temperature. In the final stage, due to the relative density close to the theoretical density and diffusion creep limited by grown grain crystal, the relative density obtained a saturated value. When the holding time is short, the relative density decreases with increasing the heating rate, and also the high heating rate can limit the carburization behavior due to the contact of samples to graphite.