Journal of the Korean Society for Heat Treatment (열처리공학회지)

The Korean Society for Heat Treatment (한국열처리공학회)
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A Study on the Precipitation Behavior of $L2_1$-type Precipitates in B2-NiAl

B2형 NiAl에 석출한 $L2_1$형 석출상의 석출거동에 관한 연구

  • Han, Chang-Suk (Dept. of Defense Science & Technology, Hoseo University) ;
  • Han, Seung-Oh (Institute of Fusion Technology, Hoseo University) ;
  • Lee, Ju-Hee (Dept. of Mechatronics Eng., Graduate School of M.T.&M., Hoseo University)
  • 한창석 (호서대학교 국방과학기술학과) ;
  • 한승오 (호서대학교 융합기술연구소) ;
  • 이주희 (호서대학교 혁신기술경영융합대학원 메카트로닉스공학과)
  • Published : 2009.11.30
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Abstract

The precipitates of $L2_1$-type $Ni_2AlHf$ phase in B2-ordered NiAl system has been observed by using transmission electron microscope (TEM). The hardness of as-quenched NiAl-Hf alloys is high due to the larger strengthening. However, age hardening of this alloy is not main effect to increase hardness compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1$-type $Ni_2AlHf$ precipitates keep a lattice coherency with the NiAl matrix. The orientation relationship between the $Ni_2 AlHf$ precipitate and the NiAl matrix is <100>$_{Ni2AlHf}$//<100>$_{NiAl}$, {001}$_{Ni2AlHf}$//{001}$_{NiAl}$. By aging treatment for long time $Ni_2AlHf$ precipitates lost their coherency and change their morphology to the spherical ones surrounded by misfit dislocations. The orientation relationship between the NiAl matrix and the $Ni_2AlHf$ precipitates, however, has been kept even after longer aging time. The lattice misfit between the $Ni_2AlHf$ precipitate and the NiAl matrix has been calculated by the selected electron diffraction patterns, and the spacings of misfit dislocations is about 4.5% at 1173 K.

Keywords

References

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