Effects of nickel on the sintering behavior of Fe-Ni compacts made from composite and elemental powders

Journal Article · Mon Apr 01 04:00:00 EST 1996 · Metallurgical Transactions, B

DOI:https://doi.org/10.1007/BF02915046· OSTI ID:260753

Hwang, K S ^[1]; Shiau, M Y ^[2]

---

1. National Taiwan Univ., Taipei (Taiwan, Province of China). Inst. of Materials Science and Engineering
2. Team Young Advanced Ceramics Co. Ltd., Taoyuan (Taiwan, Province of China)

Injection-molded Fe-Ni parts made from composite and elemental powders were prepared, and the effect of nickel on the sintering of iron compacts was investigated. Dilatometry analyses showed that the alpha-gamma phase transformation temperature of the Fe-Ni compact changed from a fixed 912 C for pure iron to a temperature range between 700 C and 912 C where two phases coexisted. The microstructure indicated that nickel impeded surface diffusion and slowed down the neck growth rate of iron powder in the early sintering stage. The dual phase and the small neck size at low temperatures suppressed the exaggerated grain growth, which usually occurs on carbonyl iron powders at 912 C. It was also observed that nickel impeded the grain growth of iron at high temperatures. Thus, by reducing the exaggerated grain growth during phase transformation, impeding the grain growth at high temperatures, and with high diffusion rates of iron in Ni-rich areas, enhanced densification was obtained for Fe-Ni systems, particularly for those systems made from composite powders. However, when coarse nickel powder was added, expansion was observed due to the presence of large pores around nickel powders. These pores were formed because of the particle rearrangement which was caused by the Kirkendall effect.

• Sponsoring Organization: USDOE
• OSTI ID: 260753
• Journal Information: Metallurgical Transactions, B, Journal Name: Metallurgical Transactions, B Journal Issue: 2 Vol. 27; ISSN MTTBCR; ISSN 0360-2141
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CASTINGS
GRAIN SIZE
IRON ALLOYS
METALLURGICAL EFFECTS
NICKEL
NICKEL ALLOYS
PARTICLE SIZE
PHASE TRANSFORMATIONS
PORE STRUCTURE
SINTERING