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Javier Vivas,Carlos Capdevila,Eberhard Altstadt,Mario Houska,Ilchat Sabirov,David San‑Martín 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2
The microstructural degradation and the creep fracture behavior of conventionally and thermomechanically treated Grade91 steel were investigated after performing small punch creep tests. A remarkable reduction in creep ductility was observedfor the samples thermomechanically treated in comparison to those conventionally treated under the tested conditions ofload (200 N) and temperature (700 °C). A change in the fracture mechanism from a ductile transgranular fracture to a brittleintergranular fracture was observed when changing from the conventionally treated to the thermomechanically treated processingcondition, leading to this drop in creep ductility. The change in the fracture mechanism was associated to the localizedconcentration of creep deformation, close to coarse M23C6carbides, at the vicinity of prior austenite grain boundaries(PAGB) in the thermomechanically treated samples. The preferential recovery experienced at the vicinity of PAGB producedthe loss of the lath structure and the coarsening of the M23C6precipitates. The electron microscopy images provided suggestthat the creep cavities nucleate in these weak recovered areas, associated to the presence of coarse M23C6. After the coalescenceof the cavities the propagation of the cracks was facilitated by the large prior austenite grain size produced during theaustenitization which favors the propagation of the cracks along grain boundaries triggering the intergranular brittle fracture. This fracture mechanism limits the potential use of the proposed thermomechanical processing routes.
Recent introduction of Gracilaria parvispora (Gracilariales, Rhodophyta) in Baja California, Mexico
Garcí,a-Rodrí,guez, Luis Daniel,Riosmena-Rodrí,guez, Rafael,Kim, Su Yeon,Ló,pez-Meyer, Melina,Orduñ,a-Rojas, Javier,Ló,pez-Vivas, Juan Manuel,Boo, Sung Min Walter de Gruyter GmbH 2013 Botanica marina Vol.56 No.2