Stable and metastable ordered phases in microcrystalline alloys Ni (Fe, Mn, Ti)
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1.10 -3
(111)
(200)
50%NI
number of neutrons
(100)
Stable and Metastable Ordered Phases In Microcrystalline Alloys Ni (Fe, Mn, Ti)
(11o)
79%Ni
V.I. GOMANKOV, V.G. FEDOTOV, V.V. SOSN1N, O.M. ZHIGALINA, and V.V. SUM1N The atomic ordering of stable and metastable phases in liquid-quenched alloys has not yet been investigated thoroughly. However, in Ni-Fe and Ni-Mn bulk products quenched from 1273 K, short-range atomic order remains. The short-range atomic order parameter ai temperature dependence suggests the existence of Ni-Fe liquid state shortrange atomic orderingY] Ni3Fe and Ni3Mn (L12 type) superlattices form in both systems after annealing at temperatures lower than 723 K in a wide concentration range.[~.2] The current study presents the results of neutron diffraction analysis of L12 microcrystalline Ni-Fe and Ni3MnNi3Ti alloy superlattices. Eutectic crystallization was supposed to take place in the Ni3Mn-Ni3Ti system, resulting in the domination of one of the phases in the microcrystals obtained. That is why the concentrational structural transition Ni3Mn ---> Ni3Ti, or L12 ---> DO24, in this system was additionally studied in bulk annealed and quenched samples. The structure of microcrystalline alloys was determined by means of neutron diffraction analysis. The analysis was carried out on a neutron diffractometer with A = 0.128 nm, neutrons with A/2 fraction being 1.5 pct. Ni62-rich microcrystalline 79NiMo (78.7 pct Ni, 18.8 pct Fe, and 2.6 pct Mo) and 50Ni (50 pct Ni and 50 pct Fe) alloys were produced by melt spinning in an Ar environment. The microcrystalline ribbons received were 50- to 80/zm thick and 10-mm wide. The microcrystalline ribbons of four Ni3Mn-Ni3Ti alloys with various Ti contents (2.5 pct, 5 pct, 10 pct, and 17.5 pct) were also produced by melt spinning. Diffraction peaks, characteristic of superlattice fcc (100) and (110) reflections, are clearly seen in neutron diffraction patterns of microcrystalline Ni-Fe alloys (Figure 1), confirming the existence of short-range atomic order of crystallization origin. For the fcc structure, el and og2 were estimated via their limiting values, -16/9 CNiCFoS2 and + 16/3 cN~cve~, respectively,t3~ where CNi and CF. are alloy concentrations and S is the long-range order parameter, calculated using the 11oo/12o0 ratio, as
V.I. GOMANKOV, Leading Researcher, formerly with the Physics of Metals Institute, currently with the Precision Alloys Institute, V.G. FEDOTOV and O.M. ZHIGALINA, Researchers, Precision Alloys Institute, and V.V. SOSNIN, Chief of Laboratory, Quality Steels Institute, are with the I,P. Bardin Central Research Institute of Iron and Steel Industry, 107005 Moscow, Russia. V.V. SUMIN, Researcher, is with the Branch of Karpov, Research Institute of Physical Chemistry, Obninsk 249020, Russia. Manuscript submitted May 11, 1992.
METALLURGICAL AND MATERIALS TRANSACTIONS A
(110)
5
3 0
15
20
25
30
35
I
I
40
~5
2~
degrees Fig. 1--Neutron diffraction patterns of 79NiMo (78.7 pct Ni, 18.8 pct Fe, and 2.6 pct Mo) and 50Ni (50 pct Ni a
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