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Comment on “The influence of H content on the relaxation spectrum of α titanium”
Scripta METALLURGICA
Vol. 3, pp. 77-80, 1969 Printed in the United States
Pergamon Press,
Inc.
COMMENT ON "THE INFLUENCE OF H CONTENT ON THE RELAXATION SPECTRUM OF a TITANIUM"
F. Povolo Department of Metallurgy Case Western Reserve University Cleveland, Ohio 44106
(Received November 8, 1968)
Bentini e% al.
(i) have recently presented some results on the internal
friction of Ti-H alloys in which they found two peaks between room temperature and approximately 300°C.
The lower temperature peak,
PI' was attributed to %he
mechanical relaxation caused by jumping of the H atoms between tetrahedral interstices in the hexagonal phase of Ti.
The second peak,
P2, was interpreted as due
to the stress-induced redistribution of H atoms from octahedral to tetrahedral interstices. I% has been demonstrated
(2) that ah internal friction peak due to isolated
point defects in h.c.p, structures can only be produced from mechanical relaxation caused by jumping of interstitial between octahedral and tetrahedral
holes.
Tetrahedral to tetrahedral jumping cannot cause relaxation and H atom pairs cannot relax unless %he pairs break up during the stress-induced ordering. an internal
Thus if
friction peak is produced by jumping of the H atoms in the hexagonal
phase of Ti, it can only be due to the stress-induced ordering of the H atoms jumping between tetrahedral and octahedral holes and the peak should be a singu-
lar one (2), i.e., produced by a process with a single relaxation time. thermore, in the Ti.
one should take into account in detail the partitioning
Fur-
of hydrogen
The peak should first increase with the H content of the sample
77
(for
78
COMMENT ON "RELAXATION
concentrations
SPECTRUM OF ~ TITANIUM"
below the solubility
limit in the ~ phase)
remain constant due to the precipitation Another formation
mechanism
Vol.
that can produce
of the hydrides
the case in the work of Bentini et al., peaks does not depend on the presence
and then decrease
(4).
or
(3).
a peak in th~ internal friction
of substitutional-interstitial pairs
3, No. 2
is the
This does not seem to be
since the appearance of the P1 and P2
of substitutional
impurities.
of the P2 peak does seem to depend on the time spent between
the hydrogenation
process and the measurement.
This effect may be due to a reduction
content or to some structural
change
in the sample
The height
of the H
since the solubility
limit
of H in a Ti is very low (3) (a maximum of I0 atomic per cent at about 320°C). In fact,
these dat~ on Ti are similar to peaks that appear in Zr-H alloys
which are strongly ageing,
influenced by H content,
thermal treatment,
and are probably associated with relaxation
(5),
deformation
and
processes within the hy-
drides. In conclusion, to a redistribution
one of the peaks observed by Bentini et al. might be due of the H atoms between the two kind of interstitial
in the a phase of Ti.
However,
about the characteristics times,
the dependence
since ~he authors
of the peaks,
ical history of the sample,
it is impossible
the mechanisms
the peaks.
that produce
do not give any information
i.e., activation
of peak height on H content,
sites
energies,
relaxation
and the thermal and mechan-
to make an accurate
hypothesis
on
This work was supported by the United States Atomic Energy Commission, Contract No. AT(II-I)-1676.
References 1.
G. G. Bentlni,
2.
F. Povolo and E. A. Bisogni,
3.
G. A. Lenning,
(1954).
C. Donolato and P. M. Strocchi, Acta Met.
15, 701
Scripta Met. 2, 405
(1968).
(1967).
C. M. Cralghead and R. J. 3affee, Trans. AIME 200, 367
Vol.
3, No. 2
COMMENT
ON "RELAXATION
SPECTRUM OF ~ TITANIUM"
4.
F. Povolo and E. A. Bisogni,
Acta Met.
i_~4, 711
5.
F. Povolo and E. A. Bisogni,
to be published
(1966).
in J. Nuc. Mat.
79
Vol. 3, pp. 77-80, 1969 Printed in the United States
Pergamon Press,
Inc.
COMMENT ON "THE INFLUENCE OF H CONTENT ON THE RELAXATION SPECTRUM OF a TITANIUM"
F. Povolo Department of Metallurgy Case Western Reserve University Cleveland, Ohio 44106
(Received November 8, 1968)
Bentini e% al.
(i) have recently presented some results on the internal
friction of Ti-H alloys in which they found two peaks between room temperature and approximately 300°C.
The lower temperature peak,
PI' was attributed to %he
mechanical relaxation caused by jumping of the H atoms between tetrahedral interstices in the hexagonal phase of Ti.
The second peak,
P2, was interpreted as due
to the stress-induced redistribution of H atoms from octahedral to tetrahedral interstices. I% has been demonstrated
(2) that ah internal friction peak due to isolated
point defects in h.c.p, structures can only be produced from mechanical relaxation caused by jumping of interstitial between octahedral and tetrahedral
holes.
Tetrahedral to tetrahedral jumping cannot cause relaxation and H atom pairs cannot relax unless %he pairs break up during the stress-induced ordering. an internal
Thus if
friction peak is produced by jumping of the H atoms in the hexagonal
phase of Ti, it can only be due to the stress-induced ordering of the H atoms jumping between tetrahedral and octahedral holes and the peak should be a singu-
lar one (2), i.e., produced by a process with a single relaxation time. thermore, in the Ti.
one should take into account in detail the partitioning
Fur-
of hydrogen
The peak should first increase with the H content of the sample
77
(for
78
COMMENT ON "RELAXATION
concentrations
SPECTRUM OF ~ TITANIUM"
below the solubility
limit in the ~ phase)
remain constant due to the precipitation Another formation
mechanism
Vol.
that can produce
of the hydrides
the case in the work of Bentini et al., peaks does not depend on the presence
and then decrease
(4).
or
(3).
a peak in th~ internal friction
of substitutional-interstitial pairs
3, No. 2
is the
This does not seem to be
since the appearance of the P1 and P2
of substitutional
impurities.
of the P2 peak does seem to depend on the time spent between
the hydrogenation
process and the measurement.
This effect may be due to a reduction
content or to some structural
change
in the sample
The height
of the H
since the solubility
limit
of H in a Ti is very low (3) (a maximum of I0 atomic per cent at about 320°C). In fact,
these dat~ on Ti are similar to peaks that appear in Zr-H alloys
which are strongly ageing,
influenced by H content,
thermal treatment,
and are probably associated with relaxation
(5),
deformation
and
processes within the hy-
drides. In conclusion, to a redistribution
one of the peaks observed by Bentini et al. might be due of the H atoms between the two kind of interstitial
in the a phase of Ti.
However,
about the characteristics times,
the dependence
since ~he authors
of the peaks,
ical history of the sample,
it is impossible
the mechanisms
the peaks.
that produce
do not give any information
i.e., activation
of peak height on H content,
sites
energies,
relaxation
and the thermal and mechan-
to make an accurate
hypothesis
on
This work was supported by the United States Atomic Energy Commission, Contract No. AT(II-I)-1676.
References 1.
G. G. Bentlni,
2.
F. Povolo and E. A. Bisogni,
3.
G. A. Lenning,
(1954).
C. Donolato and P. M. Strocchi, Acta Met.
15, 701
Scripta Met. 2, 405
(1968).
(1967).
C. M. Cralghead and R. J. 3affee, Trans. AIME 200, 367
Vol.
3, No. 2
COMMENT
ON "RELAXATION
SPECTRUM OF ~ TITANIUM"
4.
F. Povolo and E. A. Bisogni,
Acta Met.
i_~4, 711
5.
F. Povolo and E. A. Bisogni,
to be published
(1966).
in J. Nuc. Mat.
79