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					   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
                                              c.



                                 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




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                  Billet #1; 90/10; 950C




                                         Blend                            Blend

Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
                                            Ta-50%Al HEC Billets
                                                 Structure – Billet#2



                         Billet #2; 50/50; 950C                  Billet #2; 50/50; 950C




                                         Blend                            Blend

Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
                                           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             Billet #2; 50/50; 950C




Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
                                             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   Ta-10%Al T=950C 100g load

                              Hardness       126.64 (70.9-286.7)

                                  Billet 2   Ta-50%Al T=900C 50g load

                              Hardness       261.5 (31.9-306.9)




Laszlo J. Kecskes
2011 TMS Annual Meeting and Conference
February 27-March 4, 2011
                                            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

				
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