In-situ Heating Characterisation Using EBSD

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1 Webinar In-situ Heating Characterisation Using EBSD

2 Speakers Dr. Ali Gholinia Dr. Neil Othen Dr. Jenny Goulden

3 Topics Introduction to EBSD Why do in-situ experiments? EBSD equipment requirements for in-situ experiments Application examples In-situ heating stage

4 In-situ Heating Characterisation Using EBSD Dr. Jenny Goulden Oxford Instruments

$Principles of EBSD EBSD: Electron BackScatter Diffraction Automated collection & indexing of electron diffraction$ piece Materials analysed Crystalline materials, e.g.

piece Materials analysed Crystalline materials, e.g.

5 Principles of EBSD EBSD: Electron BackScatter Diffraction Automated collection & indexing of electron diffraction (Kikuchi) patterns from samples in the SEM Phosphor Screen General microstructural characterisation technique Pole piece Materials analysed Crystalline materials, e.g. Metals, ceramics, minerals, conductors and insulators Characterising: Local and macro crystallographic texture Grain boundary, grain size Phase distribution Strain distribution Detector (camera)

6 Why In-situ? In-situ experiments are performed in the SEM chamber Monitor change while experimenting on the sample Typically heating and/or tensile testing Specialised stages are used in conjunction with EBSD Increasingly used to study and understand solid state events: Microstructure development Recrystallisation and recovery Failure analysis Phase transformations and phase relationships Demonstrate importance using an ex-situ experiment

7 Ex-situ Application Local orientation maps from a Ni200 Alloy As received, Folded, 5, 10, 20 and 90 minutes annealing at 600 o C 200mm Folded 5 minutes 10 minutes 20 minutes 90 minutes Ubhi et-al, Materials Science Forum Vols (2012) pp

8 Ex-situ Application A lot of detail can be obtained from ex-situ experiments Limitations as continuity between the starting structure and final structure is lost Ideally observe the changes to a grain over time To observe and record these microstructure changes as they happen offers an additional dimension Increase in application of experiments in the SEM chamber (i.e. Insitu)

9 Analytical Challenges Analytical requirements for in-situ experiments include: Detector which operates effectively at elevated temperatures Infrared radiation can saturate the detector sensor Monitoring rapid dynamic events as they occur Requires a detection system that can collect, process and visualise EBSD data at suitable speeds Automatically collect data to monitor the microstructural changes Reliably collect maps sequentially as sample and conditions change

10 Detector Design Infrared radiation interference on the detector CCD: Silicon Background signal from thermal radiation Heater 900 C, 20 kv, 4 na Low signal to noise

11 Detector Design 2 possible solutions: Infrared filtering before the phosphor screen, typically using an additional (300 nm) Al coating on the phosphor Integrated infrared filter within the detector

12 Detector Design Background signal, heater temp 900 C, 0 na beam current Phosphor + Al 300nm coating Imperfections in coating Phosphor + Infrared filter

13 Detector Design Silicon sample, heater temp 900 C, 20 kv, 4 na Phosphor + Al coating Imperfections in coating Exposure time (220 ms) Phosphor + Infrared filter Best signal to noise, Exposure time (130 ms) NordlysMax 2 detector

14 Monitoring Dynamic Events Requirement to monitor real-time microstructural changes Need to collect EBSD maps in minutes (not hours) Requires a fast EBSD detection system EBSD data collected and indexed at hundreds of patterns a second Example application: phase transformation Austenite to Ferrite in low carbon steel High speed acquisition: each map collected in 6 minutes Captures details of dynamic events during phase transformation

15 Example: Phase Transformation 945 o C 895 o C 0 mins 895 o C 6 mins 880 o C ferrite austenite

16 Automation with Flexibility Capability to automatically collect a data sequence to record changes in microstructure Adaptability to change acquisition conditions during the run This can be demonstrated using the following application example: An Al alloy application investigating both deformation and recrystallisation Load applied maps were acquired at regular intervals Load removed, sample heated up to 320 C sequence of maps collected

17 Al 0.1% Mg - Tensile Strain and Heating GATAN Microtest EH2000 Band Contrast Local mis-orientation IPF Isochronal heating 290, 300 and 320 o C Scattered pole figures (IPF colours)

18 EBSD Solution The following application examples use: Oxford Instruments NordlysMax 2 fast detector (up to 870 Hz) integrated IR filter Oxford Instruments AZtec platform flexibility ease of Use automation quality data

19 In-situ Heating Characterisation Using EBSD Dr. Ali Gholinia Manchester University In-situ dynamic heating for Recrystallisation and Phase Transformation studies

20 Recrystallisation in Bronze and Steel Recrystallisation in Aluminium Phase transformation in Titanium Study of orientations in twin bands during phase transformation in Titanium

21 Before annealing After annealing Acknowledgements to Sylvia Campbell from MAHLE Engine Systems UK Ltd. for providing the Bronze samples.

22 IPF-X colour maps Thick black lines: High angle grain boundaries >10 Thin black lines: Low angle grain boundaries >2 Yellow lines: Twin boundaries Bronze Steel

23 Grains in random colours Thick black lines: High angle grain boundaries >10 Thin black lines: Low angle grain boundaries >2 Yellow lines: Twin boundaries Bronze Steel

24 Recrystallisation in Aluminium Al-0.1Mg Band Contrast Harvinder Singh Ubhi et al., Materials Science Forum, V.753, (2013), p

25 Recrystallisation in Aluminium Al-0.1Mg Local misorientation

26 Recrystallisation in Aluminium Al-0.1Mg IPF-Z colours In-situ heating up to 295 C of deformed Al-0.1Mg alloy

27 Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) Acknowledgements to Jack Donoghue from University of Manchester for providing the Ti samples.

28 30 C Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

29 200 C Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

30 400 C Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

31 600 C Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

32 925 C Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

33 950 C Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

34 Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

35 Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

36 Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

37 Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

38 Green: Ti-alpha (Hexagonal) Red: Ti-beta (Cubic) 20mm

39 Conclusions In-situ dynamic heating allows the direct investigation of specific grains during recrystallisation and phase transformation. This enables the study of the order of recrystallisation of each grain and link the information to their microstructure. Phase transformation studies benefit from the knowledge of orientations at high temperatures and relating them to low temperatures. This direct link would not be possible in the conventional ex-situ static heating analysis. The free surface during in-situ heating may have some unknown effect on the microstructure development, however comparison of the ex-situ and in-situ microstructures have not shown significant differences.

40 In-situ Heating Characterisation Using EBSD Dr. Neil Othen Gatan UK

41 Heating Protection for the SEM The heating stage must offer good thermal isolation, water cooling and heat protection shields for use at high temperatures Precise temperature control. The stage must be responsive, but with a high level of accuracy so transformations can be controlled and observed Stability Minimal drift throughout heating. This can be achieved through a uniform heating platform with minimal thermal gradients and good thermal insulation.

42 Heating Size of the heating stage To be suitable for techniques such as EBSD a heating stage must be compact so it can be moved and tilted to the correct orientation Imaging At high temperatures, need to consider the limitations of SEM detectors and impact of thermal electrons. A bias voltage applied to the stage can improve imaging by reducing thermal electrons from the specimen Ease of use How quickly can the SEM be returned to normal operation? For multiuser facilities minimal delay in fitting removing the heating stages maximises time running samples

43 In-situ heating stage Gatan has developed a robust universal heating stage with a novel compact design suitable for: SED and EBSD imaging. Its optimum shape ensures full compatibility with EBSD whilst a choice of user changeable shields ensures protection to the SEM is maintained. The stage enables dynamic EBSD analysis of samples with a high temperature accuracy <0.5 C and stability <0.5 C per hour up to temperatures of 950 C. Suitable for specimens up to several mm 3 in size, a bulk specimens allows easier handling and avoids mis-interpretations due to thin films and surface artefacts.

In-situ heating stage The Gatan model 525 heating stage is specifically designed to suit in-situ market requirements Small, yet powerful, with high tilt compatibility giving optimum EBSD signal

44 In-situ heating stage The Gatan model 525 heating stage is specifically designed to suit in-situ market requirements Small, yet powerful, with high tilt compatibility giving optimum EBSD signal Precise controlled heating of specimens up to several mm 3 in size - crucial to observe stable transformations A detachable specimen holder provides quick sample exchange and storage Opportunity to prepare and mount specimens away from the SEM

45 Model 525 Murano heating stage System comprises:

46 Model 525 Murano heating stage System comprises: Water-cooled base attached to the SEM stage. Base is designed to suit individual SEMs and is easy to fit/remove. SEM stage can be returned to normal use within minutes. Water cooling with a safety interlock ensures protection for the SEM stage. No water - heating power to stage is stopped.

Model 525 Murano heating stage System comprises: A transferable heating specimen holder The holder fits on to the water cooled base, its dovetail design allows it to be loaded quickly and

47 Model 525 Murano heating stage System comprises: A transferable heating specimen holder The holder fits on to the water cooled base, its dovetail design allows it to be loaded quickly and securely in under 1 minute The removable holder design allows the user to mount their specimen away from the SEM and store it if required for future work Allows airlock loading as a special option

48 Model 525 Murano heating stage System comprises: Consumable, heated specimen platform Specimen sits on centre platform and is secured using high temperature cement to ensure good thermal contact. The replaceable platform Prevents contamination between specimens. Allows individual specimen storage.

49 Model 525 Murano heating stage Consumable heated platform and loading jig allow multiple specimens to be prepared and stored.

50 SE imaging above 600 C PHOTO PENDING EBSD imaging above 600 C A choice of shielding options is available. Shield may be removed below 600 C

51 A programmable PC based temperature control provides flexibility for a range of experiments. Data logging and time stamping allows EBSD maps to be synchronise. 52

52 A compact design allows full SEM integration SEM FIB Heating stage EBSD No need for specimen re-mounting, as it is tilted from the 0 tilt loading position. Making it suitable for several analytical and imaging techniques.

53 Model 525 Murano in-situ heating stage Dynamic testing is possible in-situ in the SEM, with specifically designed heating stages. A more efficient workflow allows a single specimen to be used to study a complete temperature range. Specimens can be prepared, mounted and stored ready for use to allow quick SEM access

54 Summary EBSD coupled with in-situ dynamic heating is a powerful tool for studying microstructure in the SEM Offers an insight to material behaviour in use Modern analytical equipment makes acquiring this data a reality

55 Further reading Two in-situ EBSD application notes Tensile / Heating of Al 0.1% Mg Alloy In-situ EBSD Analysis of an Al Alloy

56 Q&A Dr. Ali Gholinia Dr. Neil Othen Dr. Jenny Goulden

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