1. PHASE ANALYSIS EXPLOSIVE WELDED Ti- Cr/Ni STEEL IN AS-RECEIVED STATE AND AFTER HEAT TREATMENT USING SYNCHROTRON Dmytro OSTROUSHKO a, Eva MAZANCOVÁ a, Karel SAKSL b, Ondrej Milkovič b EPNM2014-Kraków

2. Aim The work is focused on interface shape line, inhomogeneities in vicinity of the wave joint both in basic material and in vicinity of weld line of the Ti and Cr/Ni stainless steel (SS) matrix. Investigated weld was both in as-received state and after heat treatment carried out at 600°C/90 minutes/air. Presented phases have been identified using X-ray diffraction performed by synchrotron. The Ti , Fe-fcc, Fe-bcc and intermetallic phases Fe 2 Ti were detected at interface area. EPNM2014-Kraków

3. Experimental material Preparation of samples to phase analysis - Embedded – Polyfast, Isofast - Grinded – P300, P600, P800, P1200, P2500 - Polished 0.006 mm + H 2 O (PHOENIX 4000, Buehler) - Etched – KROLL (100ml H 2 O + 6ml HNO 3 + 3ml HF) time was about 3 second. In collaboration with the company EXPLOMET the following materials were joined Ti + SS, this bimetal consists of pure α-Ti and 18/10 Cr/Ni steel with high strength and excellent corrosion resistance. Primarily used in heavy chemical industry. EPNM2014-Kraków

4. Bonding line of Ti-Cr/Ni SS sandwich Typical wavy bonding zone Ti-Cr/Ni steel after etching Typical bonding line (interface) of the studied material figures demonstrates. After the HT Ti-Cr/Ni SS sandwich shows wavy interface in nature as it was observed after explosive bonding Ti Interface SS Typical wavy bonding zone Ti-Cr/Ni steel without etching EPNM2014-Kraków

5. Synchrotron (BW-5)DORIS III XRD measurements were carried out using the BW5 experimental station located at the DORIS III positron storage ring (energy 4.45 GeV, current 140–100 mA) at HASYLAB/DESY, Hamburg, Germany. The energy of the incident beam was 100 keV, lambda=0.124 Å. EPNM2014-Kraków

6. Synchrotron (BW-5) DORIS III The specimen was scanned shot-by-shot along a path of total length 40 mm with step width of 1mm. During each step, the sample was illuminated by highly intensive hard X-rays for 2 seconds. The resulting 2D XRD patterns were recorded using a Perkin Elmer 1621 detector. The collected data were then integrated into 2 Theta space using the FIT2D software. The sample-detector distance, detector orthogonality with respect to the incoming radiation, as well as precise radiation energy were determined by fitting a standard reference LaB6 sample. EPNM2014-Kraków

7. Synchrotron (BW-5) DORIS III 3D plot of obtained XRD patterns taken shot-by-shot going from the SS to Ti. The picture clearly indicates abrupt change of the XRD pattern corresponding to interface between this two materials. EPNM2014-Kraków

8. Synchrotron (BW-5) DORIS III XRD pattern from the interface region is shown together with patterns taken CCA 1 cm away from the interface in both direction. Ti consists of sole hcp-Ti alpha phase and the SS of fcc-Fe phase solid solution and bcc-Fe like phases. There are differences in the proportion of bcc-Fe in comparison with the sample with the HT which show their significantly lower level (approximately by 60% - diffraction maxima for images with "o"). Other intermetallic phases haven't been detected by this method. EPNM2014-Kraków

9. Synchrotron (P-07)PETRA III The second X-ray micro-diffraction experiment was performed at beamline P07 at PETRA III (positron storage ring operating at energy 6GeV with beam current 100mA). During the experiment, monochromatic synchrotron radiation of energy 80.09keV (λ = 0.01548nm) was used. EPNM2014-Kraków

10. Synchrotron (P-07)PETRA III The beam of photons was focused by compound refractive lenses down to a spot size of 2.2μm x 34μm. The specimen was scanned shot-by-shot along a straight path of total length 0,4 mm with step width of 1µm. During each step, the sample was illuminated by highly intensive hard X-rays for 0.5 seconds. The resulting 2D XRD patterns were recorded using a Perkin Elmer 1621 detector. The intensity was integrated to 2 Theta space by using the Fit2D software. EPNM2014-Kraków

11. Synchrotron (P-07)PETRA III Phase analysis from the interfacial region proved existence of the hexagonal close packed Fe 2 Ti intermetallic phase together with main matrix components fcc-Fe (austenite) and bcc-Fe (ferrite). Comparison between explosion welded (as-received) and the sample after HT testify effective reduction of intermetallic compound by the annealing. Volume percentage Fe 2 Ti in the as-prepared sample is about 17.5% while after the HT is approx. by 70% less (5.25 vol. %). EPNM2014-Kraków

12. Synchrotron (P-07)PETRA III In addition, we quantify the amount of intermetallic phase measuring from centre of the interface to both materials. The phase is visible in region wide approx. 204  m and for the annealed sample is significantly lover compared to the as-received state. The measurement proved that the HT is effective procedure to dissolute unwanted intermetallic compound and to improve the whole material lifetime. EPNM2014-Kraków

13. CONSLUSIONS The first XRD pattern showed that the interface region of both the samples probed in area 1x1 mm consist of the hcp-Ti, fcc-Fe solid solution and bcc-Fe like phases. The sample after annealing at 600 °C/90 min./air shows significantly lower amount of the bcc-Fe phase. Other intermetallic phases were not detected by synchrotron (BW5). The second experiment proved existence of the hexagonal close packed Fe2Ti intermetallic phase together with main matrix components fcc Fe (austenite) and bcc-Fe (ferrite). In order to quantify volume amount of intermetallic phase in the samples we performed Rietveld refinement of the XRD patterns. Volume percentage Fe2Ti in the as-prepared sample is about 17.5% while after the HT is ~70% less (5.25 vol.%). The measurement proved that the HT is effective procedure to dissolution unwanted intermetallic compound causing improvement of the whole material lifetime. In future works it would be useful presented results to verify using other explosively welded samples. EPNM2014-Kraków

14. ACKNOWLEDGEMENT Mobilities International Research Teams Specific Research in Metallurgical, Material and Process EngineeringRegional Materials Science and Technology Centre – Feasibility Program EXPLOMET This paper was created within the project 7AMB14SK023“Mobilities“, 02613/2013/RRC „International Research Teams“ sponsored by Northern Moravian region, within the project SP 2014/62 “Specific Research in Metallurgical, Material and Process Engineering“ and No. L01203 L “Regional Materials Science and Technology Centre – Feasibility Program“ founded by Ministry of Education, Young and Sports of Czech Republic. Special thanks belongs to EXPLOMET for an important cooperation. EPNM2014-Kraków

15. THANKS FOR YOUR ATTENTION Slovak Academy of Sciences Institute of Material Research Kosice, Slovakia EPNM2014-Kraków