1. Hot Explosive Consolidated Nanostructured Ta-Al Composites22
Hot Explosive Consolidated Nanostructured Ta-Al Composites
A. Peikrishvili, L. Kecskes, E. Chagelishvili, M. Tsiklauri and B. Godibadze
2012 EPNM’12 Symposium0
May 2-5, 2012, Strasbourg, France

2. ation and Properties of Hot Explosive Consolidated Ni-Al Composites
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 2

3. Outline Purpose Technique Precursors Results Summary of Previous Work
Current Work
Prognosis 2

4. 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

5. 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;

6. 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

7. 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 = µm
Ta- 50Al wt.%;
Al size = µm

8. Compaction Fixture Scale Up
Experimental set up for scaled-up dimensioned billets
Detonator
Specimen 1 2 3 6 4 5 7
Furnace
Explosive
Explosive Charge
Momentum Trap
Momentum Trap

9. Compaction Fixture
Scale Up

10. Pre- and Consolidated Billets
Sample Geometry
External Appearance
Pre- and Consolidated Billets

11. Ta-Al HEC Billets
Cross Sections
Ta75.88 Nb24.12
Ta83.44 Nb16.56

12. Mechanical and Electrical Properties of HEC Ta–Al Composites
. 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

13. 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..

14. Ta-10%Al HEC Billets Blend Blend Structure – Billet#1
Billet #1; 90/10; 950C
Billet #1; 90/10; 950C
Blend
Blend

15. Ta-50%Al HEC Billets Blend Blend Structure – Billet#2
Billet #2; 50/50; 950C
Billet #2; 50/50; 950C
Blend
Blend

16. Phase Chemistry Precursors
Ta-Al HEC Billets
Phase Chemistry Precursors
Al precursor

17. Phase Chemistry – Precursors
Ta-Al HEC Billets
Phase Chemistry – Precursors
Ta precursor

18. Phase Chemistry - Products
Ta-Al HEC Billets
Phase Chemistry - Products
Billet #2; 50/50; 950C
Billet #1; 90/10; 950C

19. X-ray diffraction picture
Ta-Al HEC Billets
X-ray diffraction picture
Billets #1&2; 90/10 & 50/50; 9500C

20. 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.

21. 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.

22. Hardness Measurements
Ta-Al HEC Billets
Hardness Measurements
Billet 1
Ta-10%Al T=950C 100g load
Hardness
( )
Billet 2
Ta-50%Al T=900C 50g load
( )

23. 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.

24. 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