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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.
Roger Iván Rodríguez-Vivas,Gertrudis del Socorro Basto-Estrella,Enrique Reyes-Novelo,William Arcila-Fuentes,Melina Ojeda-Chi,Iris Trinidad-Martínez,Imelda Martínez-M 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.1
Macrocyclic lactones can have adverse effects in dung beetles exposed to manure containing them. An assessment of the survival and fertility of adult Onthophagus landolti Harold fed with manure from cows treated with moxidectin was performed, as well as the emergence rate of the imagoes from the masses. Three cows (Bos indicus x B. taurus) were subcutaneously injected with 1% moxidectin (0.2 mg kg −1 b.w.) and another three were injected with 10% moxidectin (1.0 mg/kg −1 b.w.). Manure was collected from these animals one day prior to moxidectin administration, five days post-treatment in the 1% and 10% treatments, and fourteen days in the 10% treatment. Four bioassays were done: a control using manure without moxidectin; 1% moxidectin at five days post-treatment; 10% moxidectin at five days post-treatment; and 10% moxidectin at fourteen days posttreatment. In each replicate, for each pair of adult O. landolti was daily fed with 30 g manure according to the treatments. No lethal effects were observed in any of the four treatments. Sub-lethal effects (P < .05) were present in the 10% moxidectin treatments at five and fourteen days post-treatment. Fecundity was reduced by 78.2% at five days and 54.9% at fourteen days, and imago emergence was negatively affected at both times. Current moxidectin application methods may have negative effects on the environmental services provided by dung beetles, and therefore need to be modified to minimize any impacts they might have on these vital members of tropical livestock systems