ABSTRACT Conventional ferrous powder metallurgy relies on uniaxial die-pressing of powder before sintering. The operation causes particle rearrangement and deformation and the initial state of the compact ultimately determines the sintering behaviour. In this study, sintering was investigated for water-atomised iron powder compacted at three different pressure levels, with and without admixed graphite. Electron back-scatter diffraction of the powder and compacts showed a large increase in low-angle grain boundaries after compaction. The sintering of the compacts was investigated by means of dilatometry in hydrogen. The initial compaction strongly influences sintering shrinkage, particularly in the low-temperature, high-diffusivity ferrite region which can account for up to 80% of the recorded shrinkage. Only a small fraction of the total shrinkage originates from the austenite phase, even at high sintering temperatures. However, the ratio of sintering shrinkage in ferrite and austenite changes with compaction pressure, carbon content and heating rate.

中文翻译：

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压实水雾化铁粉的烧结行为：初始状态和加工条件的影响

摘要 传统的黑色金属粉末冶金依赖于粉末在烧结前的单轴模压。该操作导致颗粒重新排列和变形，压块的初始状态最终决定了烧结行为。在这项研究中，研究了在三种不同压力水平下压实的水雾化铁粉的烧结，有和没有混合石墨。粉末和压坯的电子背散射衍射显示压实后低角度晶界大幅增加。压块的烧结通过在氢气中的膨胀测定法进行研究。初始压实对烧结收缩有很大影响，特别是在低温、高扩散率铁素体区域，其可占记录收缩的 80%。即使在高烧结温度下，也只有一小部分总收缩源于奥氏体相。然而，铁素体和奥氏体的烧结收缩比随着压制压力、碳含量和加热速度而变化。