Effects of the types of raw iron powders on the microstructure and properties of Fe-29Ni-17Co Kovar alloys
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摘要: 分别以还原铁粉和羰基铁粉,与镍粉和钴粉混合制备Fe-29Ni-17Co粉末混合料,通过压制、烧结得到Fe-29Ni-17Co可伐合金烧结体试样。考察了原料铁粉类型和烧结温度等对烧结体显微组织和相关性能的影响。结果表明,由羰基铁粉制备的烧结体有较高的密度,1250 ℃烧结得到的烧结体试样相对密度达97.51 %,比由还原铁粉制得的烧结体相对密度高约1.4 %。物理力学性能测试表明,羰基铁粉较还原铁粉为原料制得的烧结体具有更好的综合性能,其硬度和抗拉强度分别为84.6HRB和533.8 MPa,热导率、平均热膨胀系数(20~400 ℃)及电阻率分别为16.45 W·m-1·K-1、4.71×10-6 K-1和0.38 Ω·cm。此外,由羰基铁粉制得的烧结体显微组织中奥氏体分布更为均匀,低温处理后组织稳定性好,马氏体相变程度低。
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关键词:
Abstract: Fe-29Ni-17Co (Kovar alloy) powder mixes were obtained by mixing nickels and cobalt powders with reduced and carbonyl iron powder respectively, and sintered Fe-29Ni-17Co samples were prepared by pressing the powder mixes and sintering at different temperatures. Microstructure and properties of the sintered Fe-29Ni-17Co samples were investigated in accordance with the types of the iron powders and sintering temperature. The results show that sintered Fe-29Ni-17Co samples prepared from the carbonyl iron powder have higher relative density and better comprehensive performance. After sintered at 1250 ℃ for 2 h in H2 atmosphere, relative density of 97.51 % (8.11 g·cm-3) was obtained for samples prepared from the carbonyl iron powders, which is 1.4 % higher than that from reduced iron powders. Hardness and tensile strength of the samples prepared from carbonyl iron powders reach 84.6HRB and 533.8 MPa, respectively, and thermal conductivity, average thermal expansion coefficient (20~400 ℃) and electrical resistivity are 16.45 W·m-1·K-1, 4.71×10-6 K-1 and 0.38 Ω·cm, respectively. More uniform austenite distribution was observed in the sintered samples prepared from carbonyl iron powders, and there have less martensite transformation after low temperature treatment.-
Key words:
- Kovar alloy /
- Powder metallurgy /
- Raw iron powder /
- Sintering temperature /
- Thermal expansion properties
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