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在铁基粉末冶金材料中,为了获得强韧化效果,磷已被作为添加元素之一。本研究利用俄歇能谱、扫描电镜及能谱仪等研究了含0.6％磷的Fe-P-C-Cu-Mo合金中磷的分布及其对性能的影响。发现在1080℃～1200℃烧结,磷在晶界的浓度高于其在晶内的浓度。在此温度范围内,烧结温度越低,磷在晶界的偏聚程度越高。当烧结后的合金中含有大量的铁素体时,磷的这种偏聚状态对合金冲击韧性的影响被合金组织的影响所掩盖。在1080℃～1240℃烧结的合金断口均为穿晶断裂。此外还观察到回火后磷的分布对合金断裂方式及机械性能影响很大。合金淬火后在200℃回火,固溶在基体中的钼具有抑制磷向晶界偏聚的作用,合金断口表现为穿晶断裂;在400℃回火,由于钼形成了碳化钼(Mo_2C),失去了抑制磷偏聚的作用,这时磷主要偏聚在晶界,造成合金沿晶断裂,冲击韧性下降;在600℃回火,由于温度较高,减少了磷向晶界偏聚的趋势,并有利于磷作长程扩散,此时磷主要偏聚在孔隙表面,使合金具有较高的冲击韧性,合金断口呈韧窝状。
In iron-based powder metallurgy materials, phosphorus has been used as one of the added elements in order to obtain the toughening effect. In this study, the distribution of phosphorus in Fe-P-C-Cu-Mo alloy containing 0.6% phosphorus and its effect on the properties were studied by Auger energy dispersive spectroscopy, scanning electron microscopy and energy dispersive spectroscopy. Found at 1080 ℃ ~ 1200 ℃ sintering, phosphorus concentration in the grain boundary is higher than its concentration in the crystal. In this temperature range, the lower the sintering temperature, the higher the degree of phosphorus segregation at the grain boundaries. When the sintered alloy contains a large amount of ferrite, the influence of this segregation state of phosphorus on the impact toughness of the alloy is masked by the effect of the alloy structure. The alloy fracture at 1080 ℃ ~ 1240 ℃ are transgranular fracture. In addition, it is also observed that the distribution of phosphorus after tempering has a great influence on the fracture mode and mechanical properties of the alloy. After quenching, the alloy was tempered at 200 ℃. Molybdenum dissolved in the matrix could inhibit the segregation of phosphorus to the grain boundaries. The fracture of the alloy was transgranular fracture. When the alloy was tempered at 400 ℃, molybdenum carbide (Mo_2C) , Losing the role of inhibiting the segregation of phosphorus. At this time, phosphorus mainly segregates in the grain boundary, resulting in fracture along the crystal and decreasing impact toughness. Tempering at 600 ° C reduces the segregation of phosphorus to the grain boundaries due to the higher temperature Trend, and is conducive to phosphorus for long-term diffusion, when phosphorus mainly segregated in the pore surface, the alloy has a higher impact toughness, alloy fracture was dimpled.