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Omega phase formation and deformation mechanism in heat treated Ti-5553 alloy under high strain rate compression
Accepted Manuscript Omega phase formation and deformation mechanism in heat treated Ti-5553 alloy under high strain rate compression Tayyeb Ali, Lin Wang, Xingwang Cheng, Anjin Liu, Xuefeng Xu PII: DOI: Reference:
S0167-577X(18)31619-7 https://doi.org/10.1016/j.matlet.2018.10.057 MLBLUE 25098
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
15 August 2018 29 September 2018 8 October 2018
Please cite this article as: T. Ali, L. Wang, X. Cheng, A. Liu, X. Xu, Omega phase formation and deformation mechanism in heat treated Ti-5553 alloy under high strain rate compression, Materials Letters (2018), doi: https:// doi.org/10.1016/j.matlet.2018.10.057
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Omega phase formation and deformation mechanism in heat treated Ti-5553 alloy under high strain rate compression Tayyeb Alia,b, Lin Wanga,b* , Xingwang Chenga,b** , Anjin Liua,b , Xuefeng Xua,b a School b National
of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing 100081, China
Abstract This research has been carried out to focus on the formation of omega phase and deformation mechanism in Ti-5553 heat treated (900ᵒC for 1-hour solid solution without aging) at high strain rate compression. Split Hopkinson Pressure Bar (SHPB) was used to apply load at room temperature and the effect was characterized with the help of analyzing tools. Results ended up with the conclusions that under high strain rate loading, omega phase formation arose when two adjacent beta planes (110)ᵦ in <111>ᵦ direction covered 1/6th distance of total separating distance between planes and deformation through mechanical twinning occurred when dislocations could not match superimposed strain rate. Key words: High strain rate, Microstructure, slips bands, Twinning, Phase transformation, Omega phase *Corresponding
author. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.
**Corresponding
author.
E-mail address: [email protected] (L. Wang), [email protected] (X. Cheng)
1. Introduction
World’s progress in the field of science and technology, always relied on materials because of their unique properties in specific environment. Beta titanium alloy under investigation (Ti –5Al–5V– 5Mo–3Cr–0.5Fe), has some exceptional properties compared to steel such as high strength to
weight ratio, high stress corrosion resistance even up to 500ᵒC, because of which it is used in aerospace industry[1-3]. Microstructural constituents, like omega phase formation, grain boundary alpha, grain boundary, volume fraction of alpha, strongly affect mechanical properties of Titanium alloys[4, 5]. As influence of omega phase on the value of hardness has been reported along with the point that omega phase acts as embryo for alpha phase formation. That is why, transformation mechanism of beta to alpha at low strain rate[6], deformation induced α″ in beta Ti-alloy [7] and affect of ‘Nb’ in Ti-5553 alloy [8] have been investigated. Efforts have also been made to know the deformation mechanisms of beta containing alpha phase Ti-alloys and its thermal stability along with twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) after aging treatment. It is predicted that by varying thermal conditions, alpha precipitates formation can be varied which could directly influence TWIP and TRIP [9]. It is concluded that TWIP and TRIP in beta phase alloy can cause strain hardening and then improve ductility during process of deformation [10, 11]. For optimization of mechanical properties, like high toughness and high strength, beta Ti-alloy’s complex microstructure must be explored and understood. Owing to comparatively low mechanical properties of Ti-alloy without aging treatment, change in phase, observation of omega phase after deformation, failure mode under high and low strain rates both in tensile and compression load, have not been explored much. This part of research mainly focused on microstructural and phase change under high strain rate compressive load. So, in this work we made a thorough investigation of Ti-5553 alloy and found some interesting facts which could be helpful in tailoring mechanical properties. 2. Experimental
Ti–5Al–5V–5Mo–3Cr–0.5Fe alloy samples of rectangular shape, in forged condition, were heat treated at 900ᵒC for 1-hour then air cooled. Specimens for SHPB were cut through wire cutting technique into cylindrical shape of 4mm height and diameter. High strain rate compressive load up to 103m/s, was set to generate high deformation rate and then specimens were cut both in parallel and perpendicular to length direction to investigate affect on microstructure. Samples for optical microscopy (OM) were prepared through grinding and polishing by using different grit size emery papers followed by diamond paste. Keller reagent as etchant, was used to reveal microstructural features. Specimens for transmission electron microscopy (TEM) were prepared through Focused Ion Beam (FIB, FIB200, FEI) technique. HRTEM (TEM, JEM-2100, JEOL) was practiced to explore the crystal structure, atomic arrangements and deformation through twinning and dislocations, while for grains orientation and phase analysis EBSD was used at 300 Kev. Specimens for EBSD were prepared through electro-polishing (5% per chloric acid, 95% acetic acid, voltage 40V). Zeiss Supra 55 field emission scanning electron microscope (SEM) embedded with Nordlys II EBSD having Oxford detection system, was used. Step size varied from specimen to specimen ranging from 0.2 to 3µm at different tilt angle and working distance. For post analysis and clarity of images, channel 5 software was used. 3. Results and discussion After heating the samples above beta transus temperature, it was verified through XRD and EBSD that only the beta phase which is the stable phase above the recrystallization temperature, was present. To study physical and microstructural response of Ti-5553 against high strain rate, specimens were subjected to SHPB test. Deformation always starts through movement of dislocations which try to accommodate coming load by deforming the material first at atomic level
then micro and macro levels. In our experiment due to high strain rate loading, dislocation could not accommodate coming load by their movement, that’s why deformation through twinning also occurred. After deformation, presence of slip lines and twins in micrographs justify the deformation through slip and twining. Fig. 1(a,b,c). Slips line’s saturation & direction were not same which varied from one grain to an other as pointed out with black circle in Fig. 1(a) this is because of the fact that every grain has different arrangement of crystal structure as shown in schematic Fig. 1(d). According to Schmid’s law of deformation, slip first occurs at those planes of atoms whose value of Schmid’s factor which based on critical resolved shear stress, is more. As beta phase of Ti alloy has BCC crystal structure and has only six [110] slip planes, each of those has two <111> directions which in total become 12 slips systems. Owing to their less density as compared to FCC metals, value of activation energy, named as critical resolved shear stress, is more which causes slip at those planes in their specific directions. According to Schmid’s law, the planes at angle of 45ᵒ to applied load or close to this, are favourable for slip. So, due to different orientation of grains, angle of dense pack planes to load, varied which then caused the variation of slip bands quantitatively from grain to grain. Material was subjected to load which passed through grains at different paths due to relative orientation between load direction and grains orientation. The dense pack planes, which were not in favourable direction to incident load, became favourable for slip against bounced back load and caused cross slips. An other reason for these cross slip bands, was the activation of less dense pack planes, such as {123}ᵦ and {112}ᵦ in <111>ᵦ direction. Slip bands appeared parallel to each other Fig. 1(a) (arrows and circles), were due to existence of parallel (110)ᵦ planes in crystal as shown in schematic Fig. 1(d). As the availability of easy slip plane varied from grain to grain, that’s why slip bands changed their direction while entering into adjacent grains, Fig. 1(a) (black circle).
As titanium alloys favor the deformation through mechanical twinning phenomenon if the load is high enough for twins to occur, due to this reason some micro and nano sized twin regions were seen, as mentioned in Fig. 1(b) (e) and (f). Because of high load, activation of slip at less dense pack planes also observed which caused cross slips Fig. 1(c). Slip bands changed their direction when entered in adjacent slip bands due to availability of easy slips planes in that direction. It is well established about omega phase that it relates to BCC parent crystal structure because (0001)ω is parallel to (111)ᵦ plane of beta and [2110]ω directions parallel to [110]ᵦ [8] [12] [13]. Phenomenon of stress induced phase transformation from beta to omega was observed whose mechanism of transformation is shown in schematic Fig. 2(a, a1, a2) [13]. When shear force equal but opposite in direction acted on two adjacent (110)ᵦ planes named as ‘A’ and ‘B’ in <111>ᵦ direction then planes covered the distance of 1/6th of total separation distance between two (110)ᵦ planes, which in the result caused the formation of hexagonal omega phase Fig. 2(b) while white, black and red arrows in Fig. 2(b), pointed out toward grain boundary, slips bands and cross slips respectively. Omega phase formation was observed in SAED pattern took from deformed region Fig. 2(b). Deformed zones and omega phase formation regions are presented in Fig. 3(a) while in Fig. 3(a1, a2) zoom in images of beta and omega phases are shown along with a schematic of omega hexagonal phase [13]. Owing to stress induced transformation, omega phase (yellow) and alpha phase (red) particles were observed in EBSD phase analysis images presented in Fig. 3(b,b1) which have been taken after deformation, while on the other hand, in un-deformed specimen, no sign of phase change but only beta phase was observed (Fig. 3(c)). As it is reported that omega phase particles act as seed crystals in formation of alpha phase and also it affects hardness value
of phase Ti alloys, So, this part of research can lead toward modification of beta phase Ti-5553 alloy’s mechanical properties, uses in load bearing applications. 4. Conclusions
Stress induced Omega phase formation occurs even in non-aged Ti-5553 alloy when load drives two adjacent (110)ᵦ planes in <111>ᵦ direction 1/6th distance of total separation distance between these planes.
Deformation through twinning happens in this alloy when dislocations can not match superimposed rate of strain.
Activation of less dense pack planes cause cross slip which can act as hindrance in movement of crack.
Acknowledgment The authors honorably acknowledge the financial assistance of the National Key Lab Foundation of China. References [1] N.G. Jones, R.J. Dashwood, D. Dye, M. Jackson, Metallurgical and Materials Transactions A, 40 (2009) 1944-1954. [2] N.G. Jones, R.J. Dashwood, D. Dye, M. Jackson, Materials Science and Engineering: A, 490 (2008) 369-377. [3] J. Huang, Z. Wang, K. Xue, Materials Science and Engineering: A, 528 (2011) 8723-8732. [4] N.L. Richards, Journal of Materials Engineering and Performance, 13 (2004) 218-225. [5] N.L. Richards, Journal of Materials Engineering and Performance, 14 (2005) 91-98. [6] P. Barriobero-Vila, J. Gussone, K. Kelm, J. Haubrich, A. Stark, N. Schell, G. Requena, Materials Science and Engineering: A, 717 (2018) 134-143.
[7] T. Yao, K. Du, Y. Hao, S. Li, R. Yang, H. Ye, Materials Letters, 182 (2016) 281-284. [8] V.C. Opini, K.N. Campo, M.G. Mello, E.S.N. Lopes, R. Caram, Materials Letters, 220 (2018) 205-208. [9] F. Sun, J.Y. Zhang, P. Vermaut, D. Choudhuri, T. Alam, S.A. Mantri, P. Svec, T. Gloriant, P.J. Jacques, R. Banerjee, F. Prima, Materials Research Letters, 5 (2017) 547-553. [10] A. Bhattacharjee, V.K. Varma, S.V. Kamat, A.K. Gogia, S. Bhargava, Metallurgical and Materials Transactions A, 37 (2006) 1423-1433. [11] F. Sun, J.Y. Zhang, M. Marteleur, T. Gloriant, P. Vermaut, D. Laillé, P. Castany, C. Curfs, P.J. Jacques, F. Prima, Acta Materialia, 61 (2013) 6406-6417. [12] S. Dubinskiy, A. Korotitskiy, S. Prokoshkin, V. Brailovski, Materials Letters, 168 (2016) 155157. [13] R. Boyer, G. Welsch, E.W. Collings, Materials properties handbook : titanium alloys, ASM International, Ohio, 2007. Figure Captions Fig. 1 OM and HRTEM micrographs after SHPB. (a) showing full and partial slip bands in grains (b) micro twins and slip bands (c) climbing of cross slips (d) arrangement of (110)ᵦ planes in grains (e, f) Twined and deformed regions Fig.2 Schematic image and TEM micrographs. (a.a1,a2) transformation of ‘β’ to ‘ω’ after application of load and their Unit cells. (b) SAED shows Beta and Omega phases pattern and bright field image shows grain boundary, slips bands and cross slips. Fig. 3 HRTEM and EBSD images. (a) shows omega and beta phases (a1, a2) are zoom in images of (a1) (b) shows beta and omega phases by red and yellows colors. (c) Before SHPB test shows all Beta phase by green color
High lights Heat treated Ti-5553 without aging, under high strain rate compression Deformation through slipping and twining Omega phase nucleation in beta phase after superimposed compression
S0167-577X(18)31619-7 https://doi.org/10.1016/j.matlet.2018.10.057 MLBLUE 25098
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
15 August 2018 29 September 2018 8 October 2018
Please cite this article as: T. Ali, L. Wang, X. Cheng, A. Liu, X. Xu, Omega phase formation and deformation mechanism in heat treated Ti-5553 alloy under high strain rate compression, Materials Letters (2018), doi: https:// doi.org/10.1016/j.matlet.2018.10.057
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Omega phase formation and deformation mechanism in heat treated Ti-5553 alloy under high strain rate compression Tayyeb Alia,b, Lin Wanga,b* , Xingwang Chenga,b** , Anjin Liua,b , Xuefeng Xua,b a School b National
of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China
Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing 100081, China
Abstract This research has been carried out to focus on the formation of omega phase and deformation mechanism in Ti-5553 heat treated (900ᵒC for 1-hour solid solution without aging) at high strain rate compression. Split Hopkinson Pressure Bar (SHPB) was used to apply load at room temperature and the effect was characterized with the help of analyzing tools. Results ended up with the conclusions that under high strain rate loading, omega phase formation arose when two adjacent beta planes (110)ᵦ in <111>ᵦ direction covered 1/6th distance of total separating distance between planes and deformation through mechanical twinning occurred when dislocations could not match superimposed strain rate. Key words: High strain rate, Microstructure, slips bands, Twinning, Phase transformation, Omega phase *Corresponding
author. School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.
**Corresponding
author.
E-mail address: [email protected] (L. Wang), [email protected] (X. Cheng)
1. Introduction
World’s progress in the field of science and technology, always relied on materials because of their unique properties in specific environment. Beta titanium alloy under investigation (Ti –5Al–5V– 5Mo–3Cr–0.5Fe), has some exceptional properties compared to steel such as high strength to
weight ratio, high stress corrosion resistance even up to 500ᵒC, because of which it is used in aerospace industry[1-3]. Microstructural constituents, like omega phase formation, grain boundary alpha, grain boundary, volume fraction of alpha, strongly affect mechanical properties of Titanium alloys[4, 5]. As influence of omega phase on the value of hardness has been reported along with the point that omega phase acts as embryo for alpha phase formation. That is why, transformation mechanism of beta to alpha at low strain rate[6], deformation induced α″ in beta Ti-alloy [7] and affect of ‘Nb’ in Ti-5553 alloy [8] have been investigated. Efforts have also been made to know the deformation mechanisms of beta containing alpha phase Ti-alloys and its thermal stability along with twinning induced plasticity (TWIP) and transformation induced plasticity (TRIP) after aging treatment. It is predicted that by varying thermal conditions, alpha precipitates formation can be varied which could directly influence TWIP and TRIP [9]. It is concluded that TWIP and TRIP in beta phase alloy can cause strain hardening and then improve ductility during process of deformation [10, 11]. For optimization of mechanical properties, like high toughness and high strength, beta Ti-alloy’s complex microstructure must be explored and understood. Owing to comparatively low mechanical properties of Ti-alloy without aging treatment, change in phase, observation of omega phase after deformation, failure mode under high and low strain rates both in tensile and compression load, have not been explored much. This part of research mainly focused on microstructural and phase change under high strain rate compressive load. So, in this work we made a thorough investigation of Ti-5553 alloy and found some interesting facts which could be helpful in tailoring mechanical properties. 2. Experimental
Ti–5Al–5V–5Mo–3Cr–0.5Fe alloy samples of rectangular shape, in forged condition, were heat treated at 900ᵒC for 1-hour then air cooled. Specimens for SHPB were cut through wire cutting technique into cylindrical shape of 4mm height and diameter. High strain rate compressive load up to 103m/s, was set to generate high deformation rate and then specimens were cut both in parallel and perpendicular to length direction to investigate affect on microstructure. Samples for optical microscopy (OM) were prepared through grinding and polishing by using different grit size emery papers followed by diamond paste. Keller reagent as etchant, was used to reveal microstructural features. Specimens for transmission electron microscopy (TEM) were prepared through Focused Ion Beam (FIB, FIB200, FEI) technique. HRTEM (TEM, JEM-2100, JEOL) was practiced to explore the crystal structure, atomic arrangements and deformation through twinning and dislocations, while for grains orientation and phase analysis EBSD was used at 300 Kev. Specimens for EBSD were prepared through electro-polishing (5% per chloric acid, 95% acetic acid, voltage 40V). Zeiss Supra 55 field emission scanning electron microscope (SEM) embedded with Nordlys II EBSD having Oxford detection system, was used. Step size varied from specimen to specimen ranging from 0.2 to 3µm at different tilt angle and working distance. For post analysis and clarity of images, channel 5 software was used. 3. Results and discussion After heating the samples above beta transus temperature, it was verified through XRD and EBSD that only the beta phase which is the stable phase above the recrystallization temperature, was present. To study physical and microstructural response of Ti-5553 against high strain rate, specimens were subjected to SHPB test. Deformation always starts through movement of dislocations which try to accommodate coming load by deforming the material first at atomic level
then micro and macro levels. In our experiment due to high strain rate loading, dislocation could not accommodate coming load by their movement, that’s why deformation through twinning also occurred. After deformation, presence of slip lines and twins in micrographs justify the deformation through slip and twining. Fig. 1(a,b,c). Slips line’s saturation & direction were not same which varied from one grain to an other as pointed out with black circle in Fig. 1(a) this is because of the fact that every grain has different arrangement of crystal structure as shown in schematic Fig. 1(d). According to Schmid’s law of deformation, slip first occurs at those planes of atoms whose value of Schmid’s factor which based on critical resolved shear stress, is more. As beta phase of Ti alloy has BCC crystal structure and has only six [110] slip planes, each of those has two <111> directions which in total become 12 slips systems. Owing to their less density as compared to FCC metals, value of activation energy, named as critical resolved shear stress, is more which causes slip at those planes in their specific directions. According to Schmid’s law, the planes at angle of 45ᵒ to applied load or close to this, are favourable for slip. So, due to different orientation of grains, angle of dense pack planes to load, varied which then caused the variation of slip bands quantitatively from grain to grain. Material was subjected to load which passed through grains at different paths due to relative orientation between load direction and grains orientation. The dense pack planes, which were not in favourable direction to incident load, became favourable for slip against bounced back load and caused cross slips. An other reason for these cross slip bands, was the activation of less dense pack planes, such as {123}ᵦ and {112}ᵦ in <111>ᵦ direction. Slip bands appeared parallel to each other Fig. 1(a) (arrows and circles), were due to existence of parallel (110)ᵦ planes in crystal as shown in schematic Fig. 1(d). As the availability of easy slip plane varied from grain to grain, that’s why slip bands changed their direction while entering into adjacent grains, Fig. 1(a) (black circle).
As titanium alloys favor the deformation through mechanical twinning phenomenon if the load is high enough for twins to occur, due to this reason some micro and nano sized twin regions were seen, as mentioned in Fig. 1(b) (e) and (f). Because of high load, activation of slip at less dense pack planes also observed which caused cross slips Fig. 1(c). Slip bands changed their direction when entered in adjacent slip bands due to availability of easy slips planes in that direction. It is well established about omega phase that it relates to BCC parent crystal structure because (0001)ω is parallel to (111)ᵦ plane of beta and [2110]ω directions parallel to [110]ᵦ [8] [12] [13]. Phenomenon of stress induced phase transformation from beta to omega was observed whose mechanism of transformation is shown in schematic Fig. 2(a, a1, a2) [13]. When shear force equal but opposite in direction acted on two adjacent (110)ᵦ planes named as ‘A’ and ‘B’ in <111>ᵦ direction then planes covered the distance of 1/6th of total separation distance between two (110)ᵦ planes, which in the result caused the formation of hexagonal omega phase Fig. 2(b) while white, black and red arrows in Fig. 2(b), pointed out toward grain boundary, slips bands and cross slips respectively. Omega phase formation was observed in SAED pattern took from deformed region Fig. 2(b). Deformed zones and omega phase formation regions are presented in Fig. 3(a) while in Fig. 3(a1, a2) zoom in images of beta and omega phases are shown along with a schematic of omega hexagonal phase [13]. Owing to stress induced transformation, omega phase (yellow) and alpha phase (red) particles were observed in EBSD phase analysis images presented in Fig. 3(b,b1) which have been taken after deformation, while on the other hand, in un-deformed specimen, no sign of phase change but only beta phase was observed (Fig. 3(c)). As it is reported that omega phase particles act as seed crystals in formation of alpha phase and also it affects hardness value
of phase Ti alloys, So, this part of research can lead toward modification of beta phase Ti-5553 alloy’s mechanical properties, uses in load bearing applications. 4. Conclusions
Stress induced Omega phase formation occurs even in non-aged Ti-5553 alloy when load drives two adjacent (110)ᵦ planes in <111>ᵦ direction 1/6th distance of total separation distance between these planes.
Deformation through twinning happens in this alloy when dislocations can not match superimposed rate of strain.
Activation of less dense pack planes cause cross slip which can act as hindrance in movement of crack.
Acknowledgment The authors honorably acknowledge the financial assistance of the National Key Lab Foundation of China. References [1] N.G. Jones, R.J. Dashwood, D. Dye, M. Jackson, Metallurgical and Materials Transactions A, 40 (2009) 1944-1954. [2] N.G. Jones, R.J. Dashwood, D. Dye, M. Jackson, Materials Science and Engineering: A, 490 (2008) 369-377. [3] J. Huang, Z. Wang, K. Xue, Materials Science and Engineering: A, 528 (2011) 8723-8732. [4] N.L. Richards, Journal of Materials Engineering and Performance, 13 (2004) 218-225. [5] N.L. Richards, Journal of Materials Engineering and Performance, 14 (2005) 91-98. [6] P. Barriobero-Vila, J. Gussone, K. Kelm, J. Haubrich, A. Stark, N. Schell, G. Requena, Materials Science and Engineering: A, 717 (2018) 134-143.
[7] T. Yao, K. Du, Y. Hao, S. Li, R. Yang, H. Ye, Materials Letters, 182 (2016) 281-284. [8] V.C. Opini, K.N. Campo, M.G. Mello, E.S.N. Lopes, R. Caram, Materials Letters, 220 (2018) 205-208. [9] F. Sun, J.Y. Zhang, P. Vermaut, D. Choudhuri, T. Alam, S.A. Mantri, P. Svec, T. Gloriant, P.J. Jacques, R. Banerjee, F. Prima, Materials Research Letters, 5 (2017) 547-553. [10] A. Bhattacharjee, V.K. Varma, S.V. Kamat, A.K. Gogia, S. Bhargava, Metallurgical and Materials Transactions A, 37 (2006) 1423-1433. [11] F. Sun, J.Y. Zhang, M. Marteleur, T. Gloriant, P. Vermaut, D. Laillé, P. Castany, C. Curfs, P.J. Jacques, F. Prima, Acta Materialia, 61 (2013) 6406-6417. [12] S. Dubinskiy, A. Korotitskiy, S. Prokoshkin, V. Brailovski, Materials Letters, 168 (2016) 155157. [13] R. Boyer, G. Welsch, E.W. Collings, Materials properties handbook : titanium alloys, ASM International, Ohio, 2007. Figure Captions Fig. 1 OM and HRTEM micrographs after SHPB. (a) showing full and partial slip bands in grains (b) micro twins and slip bands (c) climbing of cross slips (d) arrangement of (110)ᵦ planes in grains (e, f) Twined and deformed regions Fig.2 Schematic image and TEM micrographs. (a.a1,a2) transformation of ‘β’ to ‘ω’ after application of load and their Unit cells. (b) SAED shows Beta and Omega phases pattern and bright field image shows grain boundary, slips bands and cross slips. Fig. 3 HRTEM and EBSD images. (a) shows omega and beta phases (a1, a2) are zoom in images of (a1) (b) shows beta and omega phases by red and yellows colors. (c) Before SHPB test shows all Beta phase by green color
High lights Heat treated Ti-5553 without aging, under high strain rate compression Deformation through slipping and twining Omega phase nucleation in beta phase after superimposed compression