Morphology characteristics of α precipitates related to the crystal defects and the strain accommodation of variant selection in a metastableβtitanium alloy

Profound and comprehensive investigations on the morphology characteristics ofαprecipitates are essential for the microstructural control of metastableβtitanium alloys.At the very beginning of aging treatment,intragranularαprecipitates with a dot-like morphology begin to generate nearby the dislocations,then those dot-likeαprecipitates with the same crystallographic orientation tend to connect with each other to develop a lath-like morphology.With the progress of aging treatment,the orientated lath-likeαprecipitates gradually combine with each other to form the V-shaped clusters or the triangular ones.The dislocations of{110}_(β)<111>βedge type are evidenced within theβgrains,and it is found that variant selection ofαprecipitates induced by the transformation strain and the interplay betweenαvariants and the dislocations are confirmed as the key factors for the formation of the V-shaped or triangular clusters.The results of this work could provide underlying knowledge on the morphology characteristics of intraguranularαprecipitates related to the crystal defects and the strain accommodation ofαvariants in metastableβtitanium alloys.

Neotectonic transpressional intraplate deformation in eastern Eurasia: Insights from active fault systems in the southeastern Korean Peninsula

Transpression occurs in response to oblique convergence across a deformation zone in intraplate regions and plate boundaries.The Korean Peninsula is located at an intraplate region of the eastern Eurasian Plate and has been deformed under the ENE–WSW maximum horizontal compression since the late Pliocene.In this study,we analyzed short-term instrumental seismic(focal mechanism)and long-term paleoseis-mic(Quaternary fault outcrop)data to decipher the neotectonic crustal deformation pattern in the south-eastern Korean Peninsula.Available(paleo-)seismic data acquired from an NNE–SSW trending deformation zone between the Yangsan and Ulleung fault zones indicate spatial partitioning of crustal deformation by NNW–SSE to NNE–SSW striking reverse faults and NNE–SSW striking strike-slip faults,supporting a strike-slip partitioned transpression model.The instantaneous and finite neotectonic strains,estimated from the focal mechanism and Quaternary outcrop data,respectively,show discrepan-cies in their axes,which can be attributed to the switching between extensional and intermediate axes of finite strain during the accumulation of wrench-dominated transpression.Notably,some major faults,including the Yangsan and Ulsan fault zones,are relatively misoriented to slip under the current stress condition but,paradoxically,have more(paleo-)seismic records indicating their role in accommodating the neotectonic transpressional strain.We propose that fluids,heat flow,and lithospheric structure are potential factors affecting the reactivation of the relatively misoriented major faults.Our findings provide insights into the accommodation pattern of strain associated with the neotectonic crustal extrusion in an intraplate region of the eastern Eurasian Plate in response to the collision of the Indian Plate and the sub-duction of the Pacific/Philippine Sea Plates.