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<p>Fe–Co–Cu pre-alloyed powder compacts were pressureless sintered at 825–925&#xa0;°C to investigate the phase and microstructure evolution during the sintering process. It was indicated that both intragranular and grain boundaries of the α-Fe matrix grains contained Cu-rich precipitates. As the sintering temperature increased from 825 to 900&#xa0;°C, the size of Cu-rich grains precipitated at α-Fe grain boundaries increased, pinning α-Fe phase grain boundaries and limiting their grain growth. When the sintering temperature was 925&#xa0;°C, a crystal transformation from α-Fe to γ-Fe took place, namely austenite transformation, and the solubility of Cu in Fe phase increased, causing rapid dissolution of Cu-rich grains. The pinning effect of grain boundaries disappeared, leading to rapid growth of Fe matrix grains; due to the significant difference in interdiffusion capability between Cu and Fe elements, a large number of Kirkendall pores were formed during the dissolution of Cu-rich grains, resulting in an increase in the porosity of the sintered alloy. It could be seen that the austenite transformation of the Fe phase matrix and the change in the solid solubility of Cu atoms were the physical basis for the change in phase composition of the sintered alloy, and the Kirkendall effect at sintering temperatures exceeding 900&#xa0;°C led to the appearance of a large number of pores in the sintered alloy. These results were common problems in adhesives such as Fe–Cu, Fe–Cu–Co, Fe–Cu–Cr, which would help predict the changes in microstructure and properties during the sintering process of such diamond tools.</p>

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Austenite transformation and formation of Kirkendall pores in Fe–Co–Cu alloy during pressureless sintering process

  • 期刊论文

  • 发表日期：

    2025年12月10日

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  • Junjun Yang,
  • Ruoqing Wu,
  • Yuhui Chen,
  • Haojun Zhou,
  • Fenghua Luo

摘要

Fe–Co–Cu pre-alloyed powder compacts were pressureless sintered at 825–925 °C to investigate the phase and microstructure evolution during the sintering process. It was indicated that both intragranular and grain boundaries of the α-Fe matrix grains contained Cu-rich precipitates. As the sintering temperature increased from 825 to 900 °C, the size of Cu-rich grains precipitated at α-Fe grain boundaries increased, pinning α-Fe phase grain boundaries and limiting their grain growth. When the sintering temperature was 925 °C, a crystal transformation from α-Fe to γ-Fe took place, namely austenite transformation, and the solubility of Cu in Fe phase increased, causing rapid dissolution of Cu-rich grains. The pinning effect of grain boundaries disappeared, leading to rapid growth of Fe matrix grains; due to the significant difference in interdiffusion capability between Cu and Fe elements, a large number of Kirkendall pores were formed during the dissolution of Cu-rich grains, resulting in an increase in the porosity of the sintered alloy. It could be seen that the austenite transformation of the Fe phase matrix and the change in the solid solubility of Cu atoms were the physical basis for the change in phase composition of the sintered alloy, and the Kirkendall effect at sintering temperatures exceeding 900 °C led to the appearance of a large number of pores in the sintered alloy. These results were common problems in adhesives such as Fe–Cu, Fe–Cu–Co, Fe–Cu–Cr, which would help predict the changes in microstructure and properties during the sintering process of such diamond tools.