放电等离子烧结制备铁基合金

采用脉冲+恒流电流烧结方法对Fe-2Cu-2Ni-1Mo-0.8C混合粉末进行了快速烧结,通过对不同脉冲电流通电时间烧结样品的显微组织、断口形貌进行分析,并对其密度和抗弯强度进行测试,研究了粉末的脉冲+恒流电流烧结行为.结果表明：脉冲电流不仅可通过粉体产生电阻热进行烧结,还具有清洁、活化粉末颗粒表面，促进粉末烧结的作用.当脉冲峰值电流、基值电流、占空比和频率分别为3000 A、360 A、50%和50 Hz,空载恒流电流为1389 A时，经脉冲和恒流电流各烧结3 min后,合金的密度和抗弯强度分别达到最大值7.61 g/cm3和1540 MPa.该烧结材料的显微组织以珠光体为主,其中包含块状或网络状分布的铁素体、奥氏体及其少数未扩散均匀的合金相.弯曲断口呈现解理、韧窝和沿晶的混合断裂特征.

Fabrication of Iron-based Alloy by Spark Plasma Sintering

The Fe-2Cu-2Ni-1Mo-0.8C mixed powders were consolidated successfully by a pulse –constant electric current sintering process within a short sintering duration of 6 min. The sintering densification behavior was investigated by optical microscope (OM), scanning electric microscope (SEM) and back scattered electron (BSE). The results indicate that the pulse current is not only generating the Joule heat, but also has effects of cleaning and activating to the powder granules. When the peak, base, repetition frequencies and duty ratio of the pulse electric current were prechosen as 3 000 A, 360 A, 50 Hz and 50%, at the same time constant current, sintering pressure and total sintering time were prechosen as 1389 A, 30 MPa and 6 min, the alloy has optimal properties by sintering of 3 min pulse electrical current and subsequent 3 min constant electrical current. The density and bend strength of the as sintered alloy are 7.61g/cm3 and 1540 MPa, respectively. Heterogeneous microstructure containing pearlite, reticular ferrite, and austenite was observed. And the fracture mode is the mixed mode of cleavage, dimple and intergranular fracture.