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In public transport system, the equipped automated fare collection (AFC) system records travellers’ spatial and temporal information and generates a mass of data daily with more than ever attraction of interest and attention from both academics and practitioners. Advances in data availability and data mining techniques provide great opportunity to investigate various researches in an efficient and effective manner. A comprehensive literature review on the application of public transport smart card data before 2011 can be referred to [1]. As some relevant studies in recent years, [2] proposed a data fusion method to infer passengers’ behavioral attributes of the trips based on the naive Bayes classifier model. The proposed method was applied to a single railway station in Osaka, with boarding/alighting information recorded by smart card and validation using trip survey data. [3] applied a unsupervised machine learning method, continuous hidden Markov model, to imputing the missing activities for each trip chain with integration of both clustering and transition models. [4] conducted a comparison on OD matrices between survey data and smart card data, and showed that both trip demands showed high correlation, which implied that the latter might provide a more efficient while less expensive way to construct the OD matrices. As is well known, traditional survey serves as the major method to gather useful trip information for a long time, but it often takes high expense of manpower, time and monetary resources. Moreover, the gap between real trips and survey results can never be ignored. This study aims to investigate various travel purposes of the public transit passengers and develop a data analysis framework to estimate the trip purposes, which can be considered as an alternative or a complementarity to the traditional survey method.

In public transport system, the equipped automated fare collection (AFC) system records travellers’ spatial and temporal information and generates a mass of data daily with more than ever attraction of interest and attention from both academics and practitioners. Advances in data availability and data mining techniques provide great opportunity to investigate various researches in an efficient and effective manner. A comprehensive literature review on the application of public transport smart card data before 2011 can be referred to [1]. As some relevant studies in recent years, [2] proposed a data fusion method to infer passengers’ behavioral attributes of the trips based on the naive Bayes classifier model. The proposed method was applied to a single railway station in Osaka, with boarding/alighting information recorded by smart card and validation using trip survey data. [3] applied a unsupervised machine learning method, continuous hidden Markov model, to imputing the missing activities for each trip chain with integration of both clustering and transition models. [4] conducted a comparison on OD matrices between survey data and smart card data, and showed that both trip demands showed high correlation, which implied that the latter might provide a more efficient while less expensive way to construct the OD matrices. As is well known, traditional survey serves as the major method to gather useful trip information for a long time, but it often takes high expense of manpower, time and monetary resources. Moreover, the gap between real trips and survey results can never be ignored. This study aims to investigate various travel purposes of the public transit passengers and develop a data analysis framework to estimate the trip purposes, which can be considered as an alternative or a complementarity to the traditional survey method.

In public transport system, the equipped automated fare collection (AFC) system records travellers’ spatial and temporal information and generates a mass of data daily with more than ever attraction of interest and attention from both academics and practitioners. Advances in data availability and data mining techniques provide great opportunity to investigate various researches in an efficient and effective manner. A comprehensive literature review on the application of public transport smart card data before 2011 can be referred to [1]. As some relevant studies in recent years, [2] proposed a data fusion method to infer passengers’ behavioral attributes of the trips based on the naive Bayes classifier model. The proposed method was applied to a single railway station in Osaka, with boarding/alighting information recorded by smart card and validation using trip survey data. [3] applied a unsupervised machine learning method, continuous hidden Markov model, to imputing the missing activities for each trip chain with integration of both clustering and transition models. [4] conducted a comparison on OD matrices between survey data and smart card data, and showed that both trip demands showed high correlation, which implied that the latter might provide a more efficient while less expensive way to construct the OD matrices. As is well known, traditional survey serves as the major method to gather useful trip information for a long time, but it often takes high expense of manpower, time and monetary resources. Moreover, the gap between real trips and survey results can never be ignored. This study aims to investigate various travel purposes of the public transit passengers and develop a data analysis framework to estimate the trip purposes, which can be considered as an alternative or a complementarity to the traditional survey method.

In public transport system, the equipped automated fare collection (AFC) system records travellers’ spatial and temporal information and generates a mass of data daily with more than ever attraction of interest and attention from both academics and practitioners. Advances in data availability and data mining techniques provide great opportunity to investigate various researches in an efficient and effective manner. A comprehensive literature review on the application of public transport smart card data before 2011 can be referred to [1]. As some relevant studies in recent years, [2] proposed a data fusion method to infer passengers’ behavioral attributes of the trips based on the naive Bayes classifier model. The proposed method was applied to a single railway station in Osaka, with boarding/alighting information recorded by smart card and validation using trip survey data. [3] applied a unsupervised machine learning method, continuous hidden Markov model, to imputing the missing activities for each trip chain with integration of both clustering and transition models. [4] conducted a comparison on OD matrices between survey data and smart card data, and showed that both trip demands showed high correlation, which implied that the latter might provide a more efficient while less expensive way to construct the OD matrices. As is well known, traditional survey serves as the major method to gather useful trip information for a long time, but it often takes high expense of manpower, time and monetary resources. Moreover, the gap between real trips and survey results can never be ignored. This study aims to investigate various travel purposes of the public transit passengers and develop a data analysis framework to estimate the trip purposes, which can be considered as an alternative or a complementarity to the traditional survey method.

You leave Sydney and head for holidays on the South Coast. You plan to catch a quick surf, check out the boutiques and cafes, stroll around a local museum. ..

We were part of a group of 77 women travelling by ship to an Antarctic research station when our route was blocked by icebergs. We had to make a decision. Should we detour into rough open ocean to reach the target site, or abandon plans to visit Rothera Research Station and settle instead for a few days of exploring Antarctica's calmer, protected waters? This is the story of "Rothera-gate", a leadership development experience on the largest all-female expedition to Antarctica. The 2018 expedition was the culmination of a year-long strategic leadership initiative for women scientists called Homeward Bound. Men typically hold the leadership positions in STEMM (Science, Technology, Engineering, Mathematics and Medicine). In recognition of this, the Homeward Bound initiative works with women in science to enhance their opportunity to take up leadership roles globally, and contribute proactively to a sustainable world.

We were part of a group of 77 women travelling by ship to an Antarctic research station when our route was blocked by icebergs. We had to make a decision. Should we detour into rough open ocean to reach the target site, or abandon plans to visit Rothera Research Station and settle instead for a few days of exploring Antarctica's calmer, protected waters? This is the story of "Rothera-gate", a leadership development experience on the largest all-female expedition to Antarctica. The 2018 expedition was the culmination of a year-long strategic leadership initiative for women scientists called Homeward Bound. Men typically hold the leadership positions in STEMM (Science, Technology, Engineering, Mathematics and Medicine). In recognition of this, the Homeward Bound initiative works with women in science to enhance their opportunity to take up leadership roles globally, and contribute proactively to a sustainable world.

Instead of hot rolling and cold rolling followed by annealing, strip casting is a more economic and environmentally friendly way to produce transformation-induced plasticity (TRIP) steels. According to industrial practice of strip casting, rapid cooling in this work was achieved using a dip tester, and a Gleeble 3500 thermo-mechanical simulator was used to carry out the processing route. A typical microstructure of TRIP steels, which included ~0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite, was obtained. The effects of deformation (0.41 reduction) above non-recrystallisation temperature, isothermal bainite transformation temperature and the size of second phase region on microstructure and mechanical properties were studied. The steel isothermally transformed at 400 °C had the best combination of ultimate tensile strength (UTS) and total elongation (TE), whether deformation was applied or not. The deformation resulted in the improvement of mechanical properties after holding at 400 °C: the UTS increased from 590 to 696 MPa and TE decreased from 0.27 only to 0.26. It was predominantly ascribed to grain size refinement and dislocation strengthening. The studied TRIP steel had comparable mechanical properties with TRIP 690 produced commercially.

Instead of hot rolling and cold rolling followed by annealing, strip casting is a more economic and environmentally friendly way to produce transformation-induced plasticity (TRIP) steels. According to industrial practice of strip casting, rapid cooling in this work was achieved using a dip tester, and a Gleeble 3500 thermo-mechanical simulator was used to carry out the processing route. A typical microstructure of TRIP steels, which included ~0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite, was obtained. The effects of deformation (0.41 reduction) above non-recrystallisation temperature, isothermal bainite transformation temperature and the size of second phase region on microstructure and mechanical properties were studied. The steel isothermally transformed at 400 °C had the best combination of ultimate tensile strength (UTS) and total elongation (TE), whether deformation was applied or not. The deformation resulted in the improvement of mechanical properties after holding at 400 °C: the UTS increased from 590 to 696 MPa and TE decreased from 0.27 only to 0.26. It was predominantly ascribed to grain size refinement and dislocation strengthening. The studied TRIP steel had comparable mechanical properties with TRIP 690 produced commercially.

The recrystallization process of hot deformed austenite of TRIP steel was predicted using Cellular Automaton (CA) combined with the principles of physical metallurgy. A model was developed for prediction of the dynamic and static recrystallization microstructure evolution and properties of hot deformed austenite for TRIP steel. The theoretical modeling of recrystallization was based on dislocation density. The microstructure evolution of austenite recrystallization of TRIP steel (such as the grain shape and size, volume fraction, kinetics curve of recrystallization) was predicted both visually and quantitatively. The distribution and variation of the dislocation density and flow stress were also obtained, and the effects of silicon content on recrystallization for TRIP steel were analyzed. The CA calculation results were in good agreement with the measured ones.

The laboratory simulation of strip casting of dual phase (DP) and transformation-induced plasticity (TRIP) steels was carried out using heat treatments of dip-cast samples in a dilatometer. The microstructure of DP steel (0.08C-0.81Si-1.47Mn-0.03Al wt. %) consisted of ~80 % ferrite and remaining martensite with little of bainite, whereas the microstructure of TRIP steel (0.17C-1.52Si-1.61 Mn-0.03Al wt. %) consisted of ~65 % ferrite, 4% retained austenite and remaining bainite and martensite. Small amount of Widmiinstatten ferrite was also observed in both steels. The uniaxial tensile tests were carried out on sub-sized specimens. DP steel had the ultimate tensile strength (UTS) of 446 MPa at uniform elongation (e11 ) of 0.17 while TRIP steel had the UTS of 495 MPa at e11 of 0.20, which are lower than those in hot rolled steels. This can be a consequence of cast microstructure (absence of deformation), large grain size, and presence of some Widmanstiitten ferrite. In both steels the predominant fracture mode was ductile, with presence of some isolated cleavage facets associated with the second phase. TRIP steel had a more sustainable increase in strain hardening exponent than DP steel. Crussard-Jaoul model analysis has shown very weak TRIP effect, probably because of low amount of retained austenite ( 4% ).

The recrystallization process of hot deformed austenite of TRIP steel was predicted using Cellular Automaton (CA) combined with the principles of physical metallurgy. A model was developed for prediction of the dynamic and static recrystallization microstructure evolution and properties of hot deformed austenite for TRIP steel. The theoretical modeling of recrystallization was based on dislocation density. The microstructure evolution of austenite recrystallization of TRIP steel (such as the grain shape and size, volume fraction, kinetics curve of recrystallization) was predicted both visually and quantitatively. The distribution and variation of the dislocation density and flow stress were also obtained, and the effects of silicon content on recrystallization for TRIP steel were analyzed. The CA calculation results were in good agreement with the measured ones.

Bake hardening is a phenomenon where freshly generated dislocations get pinned down by the migrating carbon atoms under the influence of temperature employed in paint baking shop. Experimentally, a minimal 2% deformation is given to generate such new dislocations. On the other hand, after bainitic transformation, steel contains a large number of dislocations as well as excess carbon atoms in bainite, a combination of which is capable of producing bake hardening effect. In the current analysis, one grade of transformation induced plasticity aided steel was chosen to study the effect of isothermal bainitic transformation on subsequent bake hardening response, without giving any deformation assuming that the previous treatment would have generated sufficient dislocations which could be pinned down by the migrating carbon atoms under the influence of thermal treatment of the bake hardening process. The final microstructure was characterised by many techniques, using Thermo-Calc, optical microscopy, XRD analysis and 3-DAP. A good agreement was observed amongst all the techniques employed.

Bake hardening is a phenomenon where freshly generated dislocations get pinned down by the migrating carbon atoms under the influence of temperature employed in paint baking shop. Experimentally, a minimal 2% deformation is given to generate such new dislocations. On the other hand, after bainitic transformation, steel contains a large number of dislocations as well as excess carbon atoms in bainite, a combination of which is capable of producing bake hardening effect. In the current analysis, one grade of transformation induced plasticity aided steel was chosen to study the effect of isothermal bainitic transformation on subsequent bake hardening response, without giving any deformation assuming that the previous treatment would have generated sufficient dislocations which could be pinned down by the migrating carbon atoms under the influence of thermal treatment of the bake hardening process. The final microstructure was characterised by many techniques, using Thermo-Calc, optical microscopy, XRD analysis and 3-DAP. A good agreement was observed amongst all the techniques employed.

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.

The effect of thermomechanical processing (TMP) parameters on the microstructure of the low Si, Al-added Ti-Mo TRIP steel was investigated using Gleeble 3500 thermo-mechanical simulator. The results showed that the formation of a significant volume fraction of polygonal ferrite is essential for the retained austenite presence in the microstructure of the TRIP steel.

The effect of thermomechanical processing (TMP) parameters on the microstructure of the low Si, Al-added Ti-Mo TRIP steel was investigated using Gleeble 3500 thermo-mechanical simulator. The results showed that the formation of a significant volume fraction of polygonal ferrite is essential for the retained austenite presence in the microstructure of the TRIP steel.

The effect of thermomechanical processing (TMP) parameters on the microstructure of the low Si, Al-added Ti-Mo TRIP steel was investigated using Gleeble 3500 thermo-mechanical simulator. The results showed that the formation of a significant volume fraction of polygonal ferrite is essential for the retained austenite presence in the microstructure of the TRIP steel.

The effect of thermomechanical processing (TMP) parameters on the microstructure of the low Si, Al-added Ti-Mo TRIP steel was investigated using Gleeble 3500 thermo-mechanical simulator. The results showed that the formation of a significant volume fraction of polygonal ferrite is essential for the retained austenite presence in the microstructure of the TRIP steel.

The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, an increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, an increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, an increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fractions of polygonal ferrite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interrupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behaviour as a function of plastic strain. X-ray analysis was used to characterise the volume fraction and carbon content of retained austenite. Transmission electron microscopy was utilised to analyse the effect of bainitic ferrite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity (TRIP) mechanism during the early stages of deformation for a microstructure containing 15% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism when there is 50% of polygonal ferrite in the microstructure. The bainitic ferrite morphology affects the deformation mode of retained austenite during straining. The polygonal ferrite behaviour during straining depends on dislocation substructure formed due to the deformation and the additional mobile dislocations caused by the TRIP effect. Operation of TRIP or twinning mechanisms depends not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.

The influence of the thermal cycle and austempering treatment on the mechanical behavior of a 0.56C–1.43Si–0.58Mn–0.47Cr (wt%) steel has been investigated. The thermal cycle consisted of heating the steel to 800°C or 900°C, in the intercritical and austenitic region respectively, fast cooling down to 600°C or 400°C, followed by 300 s hold. After austempering the materials were cooled at different rates and then submitted to tensile testing. The total elongation of 15–20% and tensile strength of 1300–1400 MPa were reached after heating to 900°C and transformation at 400°C. The strain-induced austenite transformation to martensite during the plastic deformation (Transformation Induced Plasticity Effect) is responsible for this combination of high strength and ductility. Silicon acts to stabilize the austenite during austempering. However, the stabilized austenite can be transformed and the microstructure modified, resulting in the formation of others constituents such as bainitic ferrite, upper bainite and martensite.

The influence of the thermal cycle and austempering treatment on the mechanical behavior of a 0.56C–1.43Si–0.58Mn–0.47Cr (wt%) steel has been investigated. The thermal cycle consisted of heating the steel to 800°C or 900°C, in the intercritical and austenitic region respectively, fast cooling down to 600°C or 400°C, followed by 300 s hold. After austempering the materials were cooled at different rates and then submitted to tensile testing. The total elongation of 15–20% and tensile strength of 1300–1400 MPa were reached after heating to 900°C and transformation at 400°C. The strain-induced austenite transformation to martensite during the plastic deformation (Transformation Induced Plasticity Effect) is responsible for this combination of high strength and ductility. Silicon acts to stabilize the austenite during austempering. However, the stabilized austenite can be transformed and the microstructure modified, resulting in the formation of others constituents such as bainitic ferrite, upper bainite and martensite.

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fractions of polygonal ferrite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interrupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behaviour as a function of plastic strain. X-ray analysis was used to characterise the volume fraction and carbon content of retained austenite. Transmission electron microscopy was utilised to analyse the effect of bainitic ferrite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity (TRIP) mechanism during the early stages of deformation for a microstructure containing 15% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism when there is 50% of polygonal ferrite in the microstructure. The bainitic ferrite morphology affects the deformation mode of retained austenite during straining. The polygonal ferrite behaviour during straining depends on dislocation substructure formed due to the deformation and the additional mobile dislocations caused by the TRIP effect. Operation of TRIP or twinning mechanisms depends not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fractions of polygonal ferrite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interrupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behaviour as a function of plastic strain. X-ray analysis was used to characterise the volume fraction and carbon content of retained austenite. Transmission electron microscopy was utilised to analyse the effect of bainitic ferrite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity (TRIP) mechanism during the early stages of deformation for a microstructure containing 15% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism when there is 50% of polygonal ferrite in the microstructure. The bainitic ferrite morphology affects the deformation mode of retained austenite during straining. The polygonal ferrite behaviour during straining depends on dislocation substructure formed due to the deformation and the additional mobile dislocations caused by the TRIP effect. Operation of TRIP or twinning mechanisms depends not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.

The influence of the thermal cycle and austempering treatment on the mechanical behavior of a 0.56C–1.43Si–0.58Mn–0.47Cr (wt%) steel has been investigated. The thermal cycle consisted of heating the steel to 800°C or 900°C, in the intercritical and austenitic region respectively, fast cooling down to 600°C or 400°C, followed by 300 s hold. After austempering the materials were cooled at different rates and then submitted to tensile testing. The total elongation of 15–20% and tensile strength of 1300–1400 MPa were reached after heating to 900°C and transformation at 400°C. The strain-induced austenite transformation to martensite during the plastic deformation (Transformation Induced Plasticity Effect) is responsible for this combination of high strength and ductility. Silicon acts to stabilize the austenite during austempering. However, the stabilized austenite can be transformed and the microstructure modified, resulting in the formation of others constituents such as bainitic ferrite, upper bainite and martensite.

This paper reports on a study that investigated students' metacognitive engagement of in both out-of-school and classroom settings, as they participated in an amusement park physics program. Students from two schools that participated in the program worked in groups to collectively solve novel physics problems that engaged their individual metacognition. Their conversations and behavioral dispositions during problem solving were digitally audio-recorded on devices that they wore or placed on the tables where groups worked on the assigned physics problems. The students also maintained reflection journals on the strategies they employed to manage their own understanding as well as learning processes. Prior to the amusement park physics discourse, the students completed a specially-developed questionnaire instrument. This provided signposts of the students' metacognitive engagement during group problem-solving at the park and subsequent related physics learning tasks back in the classroom. This data, added to field notes arising from observations, and formal and informal interviews during post-visit learning activities provided the data corpus on the students' metacognitive engagement. Analysis of this data revealed three types of metacognitive engagement during group learning tasks: collaborative and consensus-seeking, highly argumentative, and eclectic, resulting from high levels of dissonance. In both cases, evidence of individual students' deeper understandings, which manifested through students' cognitive and social behaviors, demonstrated the invocation of metacognition to varying degrees. The novel physics problems tackled by the students created situations where discrepancies between their prior knowledge and the direct experiences enabled them to explicate their thinking through dispositions of behavior.

This paper reports on a study that investigated students' metacognitive engagement of in both out-of-school and classroom settings, as they participated in an amusement park physics program. Students from two schools that participated in the program worked in groups to collectively solve novel physics problems that engaged their individual metacognition. Their conversations and behavioral dispositions during problem solving were digitally audio-recorded on devices that they wore or placed on the tables where groups worked on the assigned physics problems. The students also maintained reflection journals on the strategies they employed to manage their own understanding as well as learning processes. Prior to the amusement park physics discourse, the students completed a specially-developed questionnaire instrument. This provided signposts of the students' metacognitive engagement during group problem-solving at the park and subsequent related physics learning tasks back in the classroom. This data, added to field notes arising from observations, and formal and informal interviews during post-visit learning activities provided the data corpus on the students' metacognitive engagement. Analysis of this data revealed three types of metacognitive engagement during group learning tasks: collaborative and consensus-seeking, highly argumentative, and eclectic, resulting from high levels of dissonance. In both cases, evidence of individual students' deeper understandings, which manifested through students' cognitive and social behaviors, demonstrated the invocation of metacognition to varying degrees. The novel physics problems tackled by the students created situations where discrepancies between their prior knowledge and the direct experiences enabled them to explicate their thinking through dispositions of behavior.

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0.3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fractions of polygonal ferrite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interrupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behaviour as a function of plastic strain. X-ray analysis was used to characterise the volume fraction and carbon content of retained austenite. Transmission electron microscopy was utilised to analyse the effect of bainitic ferrite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity (TRIP) mechanism during the early stages of deformation for a microstructure containing 15% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism when there is 50% of polygonal ferrite in the microstructure. The bainitic ferrite morphology affects the deformation mode of retained austenite during straining. The polygonal ferrite behaviour during straining depends on dislocation substructure formed due to the deformation and the additional mobile dislocations caused by the TRIP effect. Operation of TRIP or twinning mechanisms depends not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.

The influence of the thermal cycle and austempering treatment on the mechanical behavior of a 0.56C–1.43Si–0.58Mn–0.47Cr (wt%) steel has been investigated. The thermal cycle consisted of heating the steel to 800°C or 900°C, in the intercritical and austenitic region respectively, fast cooling down to 600°C or 400°C, followed by 300 s hold. After austempering the materials were cooled at different rates and then submitted to tensile testing. The total elongation of 15–20% and tensile strength of 1300–1400 MPa were reached after heating to 900°C and transformation at 400°C. The strain-induced austenite transformation to martensite during the plastic deformation (Transformation Induced Plasticity Effect) is responsible for this combination of high strength and ductility. Silicon acts to stabilize the austenite during austempering. However, the stabilized austenite can be transformed and the microstructure modified, resulting in the formation of others constituents such as bainitic ferrite, upper bainite and martensite.

The effects of pre-straining and bake hardening on the mechanical behaviour and microstructural changes were studied in two CMnSi TRansformation-Induced Plasticity (TRIP) steels with different microstructures after intercritical annealing. The TRIP steels before and after pre-straining and bake hardening were characterised by X-ray diffraction, optical microscopy, transmission electron microscopy, three dimensional atom probe and tensile tests. Both steels exhibited discontinuous yielding behaviour and a significant strength increase with some reduction in ductility after pre-straining and bake hardening treatment. The following main microstructural changes are responsible for the observed mechanical behaviours: a decrease in the volume fraction of retained austenite, an increase in the dislocation density and the formation of cell substructure in the polygonal ferrite, higher localized dislocation density in the polygonal ferrite regions adjacent to martensite or retained austenite, and the precipitation of fine iron carbides in bainite and martensite. The mechanism for the observed yield point phenomenon in both steels after treatment was analysed.

Transmission electron microscopy and atom probe tomography revealed a significant increase in the number density of NbMoFeC clusters and fine particles after 4% pre-straining and bake hardening of transformation-induced plasticity steel alloyed with Nb and Mo. Cottrell atmospheres were detected in the non-alloyed CMnSi steel both before and after pre-straining and bake hardening.

Transmission electron microscopy and atom probe tomography revealed a significant increase in the number density of NbMoFeC clusters and fine particles after 4% pre-straining and bake hardening of transformation-induced plasticity steel alloyed with Nb and Mo. Cottrell atmospheres were detected in the non-alloyed CMnSi steel both before and after pre-straining and bake hardening.

Transmission electron microscopy and atom probe tomography revealed a significant increase in the number density of NbMoFeC clusters and fine particles after 4% pre-straining and bake hardening of transformation-induced plasticity steel alloyed with Nb and Mo. Cottrell atmospheres were detected in the non-alloyed CMnSi steel both before and after pre-straining and bake hardening.

The strengthening mechanism responsible for the unique combination of ultimate tensile strength and elongation in a multiphase Fe-0.2C-1.5Mn-1.2Si-0. 3Mo-0.6Al-0.02Nb (wt%) steel was studied. The microstructures with different volume fraction of polygonal ferrite, bainite and retained austenite were simulated by controlled thermomechanical processing. The interrupted tensile test was used to study the bainitic ferrite, retained austenite and polygonal ferrite behavior as a function of plastic strain. X-ray analysis was used to characterize the volume fraction and carbon content of retained austenite. TEM and heat-tinting were utilized to analyze the effect of bainitic ferrite morphology on the strain induced transformation of retained austenite and retained austenite twinning as a function of strain in the bulk material. The study has shown that the austenite twinning mechanism is more preferable than the transformation induced plasticity mechanism during the early stages of deformation for a microstructure containing 15% polygonal ferrite, while the transformation induced plasticity effect is the main mechanism in when there is 50% of polygonal ferrite in the microstructure. The bainitic ferrite morphology affects the deformation mode of retained austenite during straining. The polygonal ferrite behavior during straining depends on dislocation substructure formed due to the deformation and the additional mobile dislocations caused by the TRIP effect. TRIP and TWIP effects depend not only on the chemical and mechanical stability of retained austenite, but also on the interaction of the phases during straining.

Transmission electron microscopy and atom probe tomography revealed a significant increase in the number density of NbMoFeC clusters and fine particles after 4% pre-straining and bake hardening of transformation-induced plasticity steel alloyed with Nb and Mo. Cottrell atmospheres were detected in the non-alloyed CMnSi steel both before and after pre-straining and bake hardening.

Complex multiphase microstructures were obtained in transformation induced plasticity C–Mn–Si–(Nb–Al–Mo) steels by simulated controlled thermomechanical processing. These microstructures were characterized using transmission electron microscopy, X-ray diffraction and three-dimensional atom probe tomography (APT), which was used to determine the partitioning of elements between different phases and microconstituents. The measured carbon concentration (∼0.25 at%) in the ferrite of carbide-free bainite was higher than expected from para-equilibrium between the austenite and ferrite, while the concentrations of substitutional elements were the same as in the parent austenite suggesting that incomplete bainite transformation occurred. In contrast, the distribution of substitutional elements between the ferrite lath and austenite in carbide-containing bainite indicated a complete bainite reaction. The average carbon content in the retained austenite (3.2 ± 1.6 at%) was somewhat higher than the T0 limit. On the basis of the APT measured composition, the calculated Ms temperatures for retained austenite were above room temperature, indicating its low chemical stability.

Complex multiphase microstructures were obtained in transformation induced plasticity C–Mn–Si–(Nb–Al–Mo) steels by simulated controlled thermomechanical processing. These microstructures were characterized using transmission electron microscopy, X-ray diffraction and three-dimensional atom probe tomography (APT), which was used to determine the partitioning of elements between different phases and microconstituents. The measured carbon concentration (∼0.25 at%) in the ferrite of carbide-free bainite was higher than expected from para-equilibrium between the austenite and ferrite, while the concentrations of substitutional elements were the same as in the parent austenite suggesting that incomplete bainite transformation occurred. In contrast, the distribution of substitutional elements between the ferrite lath and austenite in carbide-containing bainite indicated a complete bainite reaction. The average carbon content in the retained austenite (3.2 ± 1.6 at%) was somewhat higher than the T0 limit. On the basis of the APT measured composition, the calculated Ms temperatures for retained austenite were above room temperature, indicating its low chemical stability.

Complex multiphase microstructures were obtained in transformation induced plasticity C–Mn–Si–(Nb–Al–Mo) steels by simulated controlled thermomechanical processing. These microstructures were characterized using transmission electron microscopy, X-ray diffraction and three-dimensional atom probe tomography (APT), which was used to determine the partitioning of elements between different phases and microconstituents. The measured carbon concentration (∼0.25 at%) in the ferrite of carbide-free bainite was higher than expected from para-equilibrium between the austenite and ferrite, while the concentrations of substitutional elements were the same as in the parent austenite suggesting that incomplete bainite transformation occurred. In contrast, the distribution of substitutional elements between the ferrite lath and austenite in carbide-containing bainite indicated a complete bainite reaction. The average carbon content in the retained austenite (3.2 ± 1.6 at%) was somewhat higher than the T0 limit. On the basis of the APT measured composition, the calculated Ms temperatures for retained austenite were above room temperature, indicating its low chemical stability.

Complex multiphase microstructures were obtained in transformation induced plasticity C–Mn–Si–(Nb–Al–Mo) steels by simulated controlled thermomechanical processing. These microstructures were characterized using transmission electron microscopy, X-ray diffraction and three-dimensional atom probe tomography (APT), which was used to determine the partitioning of elements between different phases and microconstituents. The measured carbon concentration (∼0.25 at%) in the ferrite of carbide-free bainite was higher than expected from para-equilibrium between the austenite and ferrite, while the concentrations of substitutional elements were the same as in the parent austenite suggesting that incomplete bainite transformation occurred. In contrast, the distribution of substitutional elements between the ferrite lath and austenite in carbide-containing bainite indicated a complete bainite reaction. The average carbon content in the retained austenite (3.2 ± 1.6 at%) was somewhat higher than the T0 limit. On the basis of the APT measured composition, the calculated Ms temperatures for retained austenite were above room temperature, indicating its low chemical stability.