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http://dx.doi.org/10.5228/KSPP.2008.17.4.240

Effect of Alloying Elements(Mn, Mo, B) on the High Temperature Deformation Behavior of Low Thermal Expansion Fe-Ni-Co Alloy  

Lee, Kee-Ahn (안동대학교 신소재공학부)
Yun, Ae-Cheon (안동대학교 신소재공학부 청정소재기술연구센터)
Park, Jung-Chul (포항산업과학연구원 신뢰성연구센터)
NamKung, Jung (포항산업과학연구원 부품신소재연구센터)
Kim, Mun-Chul (포항산업과학연구원 부품신소재연구센터)
Publication Information
Transactions of Materials Processing / v.17, no.4, 2008 , pp. 240-248 More about this Journal
Abstract
The effect of alloying elements(Mn, S, Mo, B) on the high temperature deformation behavior of Fe-29%Ni-17%Co (Kovar) alloy were investigated. And the effect of high temperature oxidation on the hot ductility was also studied. The hot ductility of Kovar alloy was drastically increased with the addition of Mn and lowering of S content. It has been found that the brittle intergranular fracture at high temperature cracking is closely associated with the FeS sulfide along the grain boundary. When Mn was added, the type of sulfide was changed to MnS from FeS and ductile intergranular fracture and transgranular fracture were promoted. The formation of oxide layer was found to have minimized the hot ductility of the Kovar alloy significantly. Grain boundary micro-cracks in the internal oxide region were noted following deformation due to high temperature, one of which acting as a notch that caused the poor hot workability of the oxidized specimen. The addition of Mo to the Kovar alloy could also retard the decrease in the hot ductility of the oxidized specimen through the prevention of notching due to internal oxidation. Hot ductility was remarkably improved by the addition of Boron. The improvement of hot ductility results from the grain boundary migration mainly due to the dynamic recrystallization at lower temperature range ($900{\sim}1000^{\circ}C$).
Keywords
Hot Ductility; High Temperature Deformation Behavior; Fe-29%Ni-17%Co; Mn; Mo; B;
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