Transcript No Slide Title

Hot Explosive Consolidated
Nanostructured Ta-Al
22
Composites
A. Peikrishvili, L. Kecskes, E. Chagelishvili, M. Tsiklauri and B. Godibadze
2012 EPNM’12 Symposium0
May 2-5, 2012, Strasbourg, France
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Fabrication of Hot Explosive Consolidated
Nanostructured Ta-Al Composites
ation and Properties of Hot Explosive
Consolidated Ni-Al Composites
A.B. Peikrishvili, E. Sh. Chagelishvili, M.V. Tsiklauri, B. A. Godibadze and
Tsulukidze Institute of Mining and Technology
Georgian Academy of Sciences
L. J. Kecskes
Weapons and Materials Research Directorate
US Army Research Laboratory
at
2012 EPMN’12 Symposium
May 2-5, 2012, Strasbourg, France
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Outline
• Purpose
• Technique
• Precursors
• Results
• Summary of Previous Work
• Current Work
• Prognosis
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Background
Ta-Al precursors form a reactive system and, as a result, it
is possible to conduct SHS processes.
Variants of alternative methods such as Hot Explosive
Compaction (HEC) in combination with SHS reactions are
being tried
Advantages are: short processing times, high pressures,
and high temperatures
Non-toxic intermetallic replacements for various
applications
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Tantalum Aluminides
Background
Tantalum Aluminides represent a ‘model’ material for
the Army and Nuclear Reactors.
Equilibrium Phase Relations
Four intermetallics
Ta2Al Tm=
2,100C;
TaAl
Tm=
1,770C;
TaAl2 Tm=
1,594C;
TaAl3 Tm=
1,551C;
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Hot Explosive Compaction
The Technique
Step 1:
sample were consolidated at room temperatures to
increase their predensity and to activate consolidating
particles surfaces.
Step 2:
Preliminary predensified billets were reloaded second
time at 950C with intensity of compression under 10GPa.
Advantages/Disadvantages:
requires less energy and time than conventional
processing; but scaling is an issue
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Scale-Up
Motivation
The blends of coarse Al and nanoscale Ta with
dimension 60-80nm were used in
Subsequent experiments provided obtaining billets with
dimensions 10mm × 50mm.
Ta-10Al wt.%;
Al size = 10-15 µm
Ta- 50Al wt.%;
Al size = 10-15 µm
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Compaction Fixture
Scale Up
Experimental set up for scaled-up dimensioned billets
Detonator
7
Specimen
Furnace
4
3
2
Explosive
1
Explosive Charge
Momentum Trap
5
4
6
Momentum Trap
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Compaction Fixture
Scale Up
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Sample Geometry
External Appearance
Pre- and Consolidated Billets
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-Al HEC Billets
Cross Sections
• Ta75.88 Nb24.12
• Ta83.44 Nb16.56
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Mechanical and Electrical Properties of
HEC Ta–Al Composites
c.
.
In Figure there is presented the results of measurement of mechanical properties (elasticity Young
modulus – E, relaxation Q-1 (Q is the quality factor of vibrating sample) for HEC Ta-Al composites.
It is seen the considerable changes in their mechanical and electrical properties depending on
compositions. In particular, the larger relaxation maximum for Ta 50 % - Al 50 % composition could be
apparently related with relaxation on grain boundaries. In this case the peak height depends on the area
of grains which is maximal when the volume ratios of both phases are equal.
Besides it, the formation new aluminade phases could contribute this effect what should be tested by
additional X-ray measurements which are under way
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Mechanical and Electrical Properties of
HEC Ta–Al Composites
Correspondingly, this effect in mechanical properties is accompanied by a considerable
increase in resistivity and resistivity temperature factor for Ta 50 % - Al 50 % composition..
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-10%Al HEC Billets
Structure – Billet#1
Billet #1; 90/10; 950C
Blend
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Billet #1; 90/10; 950C
Blend
Ta-50%Al HEC Billets
Structure – Billet#2
Billet #2; 50/50; 950C
Blend
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Billet #2; 50/50; 950C
Blend
Ta-Al HEC Billets
Phase Chemistry Precursors
Al precursor
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-Al HEC Billets
Phase Chemistry – Precursors
Ta precursor
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-Al HEC Billets
Phase Chemistry - Products
Billet #1; 90/10; 950C
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Billet #2; 50/50; 950C
Ta-Al HEC Billets
X-ray diffraction picture
Billets #1&2; 90/10 & 50/50; 9500C
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-Al HEC Billets
Discussion
Previous results connected with HEC Ni-Al and Ti-Al composites, the current
application of HEC to Ta-Al composites seems to be promising. It was shown in
our previous work that application of high temperatures and HEC of composites
of Ni(Ti)-Al could not fully result in intermetallic compounds. HEC of Ni-Al
composites at 1000C in spite of having good density and correct geometry provided
only, resulted only partially of intermetallic compounds of Ni-Al composites.
Analyzing the situation of the formation of intermetallics it was concluded that the
reason is low intensity of compression due to low pre-density of the HEC
precursors.
In contrast to Ni(Ti)-Al composites, the use of Ta-Al precursors seems to be more
promising, from the standpoint of features of explosive consolidation processes and
formation of intermetallic compounds. This is the high density of Ta powder (16.4
g/cm3) and the high reactivity of Ta-Al system. Application of HEC technology
may be solved previously fixed problems, based on developed of high intensity of
compression (loading) and high consolidation needed for initiation of SHS
processes during heating.
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-Al HEC Billets
Discussion
Results of the X-ray investigation show that in contrast to pure
Ta & Al diffraction of the precursors, the Ta-Al HEC samples
have different phase content. It is difficult to recognize and
identify the pure Ta and Al phases.
The appearance of new lines of Ta-10%Al & Ta-50%Al
composites indicates that there were chemical reactions and
intermetallic compounds formed.
Unfortunately, because of pure database for X-ray analyses and
short period before EPNM’11 symposium, correct
identification of the as-formed intermetallics in the Ta-Al system
was not yet possible.
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-Al HEC Billets
Hardness Measurements
Billet 1
Hardness
Billet 2
Hardness
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Ta-10%Al T=950C 100g load
126.64 (70.9-286.7)
Ta-50%Al T=900C 50g load
261.5 (31.9-306.9)
Interim Summary
In whole taking into account the obtained results undoubtedly may be underline of advantages
of application Ta based precursors in explosive consolidation technology due to their high
density, high elasticity and high reactivity. The all mentioned characteristics provides
development of high intensity of dynamic compression, essentially to increase the plastic flow of
consolidated grain surfaces and easier formation of rigid common boundaries between the
separate grains and syntheses of new intermetalic compounds.
The results presented in current report may be considered as a preliminary results prepared
personally for EPNM’11 symposium showing some advantages of application Ta-Al precursors
in contrast to another reactive systems such as Ni-Al and Ti-Al. The preliminary investigation
shows that application of nanoscale Ta-Al precursors in HEC technology allows to fabricate high
dense billets without cracks and formed intermetallic compounds when in case of coarse Ni(Ti)Al precursors it was impossible.
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
Future Work
Improve particle size matching and achieve full consolidation
Increase Al content of Ta(Al)
Modify relative ratio of precursors and intermetallics in scaled up products
Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011