Microstructural control and optimization of Haynes 282 manufactured through laser powder bed fusion

The microstructure and properties of alloy Haynes 282 produced through laser powder bed fusion were investigated as a function of the post-deposition heat-treatment. Scanning electron microscopy and X-ray diffraction were utilized to characterize the microstructure, whilst electro-thermal mechanical testing was used to evaluate the tensile and creep properties at 900 °C. In the as-deposited state, the initial microstructure consisted of the γ and γʹ phases along with M6C and M23C6 carbides. These carbides were observed to govern the recrystallization behaviour of the material and resulted in a minimum recrystallization temperature of 1240 °C. Following post-deposition heat-treatments, the microstructures consisted of a monomodal distribution of γʹ with M6C and M23C6 carbides along the grain boundaries. Tertiary γʹ particles were found to form in the vicinity of carbides in samples that employed a γʹ super-solvus step prior to ageing at 788 °C. The tensile properties were found to be similar in all heat-treated states, consistent with the minimal differences observed in the microstructures. In contrast, significant differences in the creep behaviour of the alloy were observed following the different heat-treatments, although no correlation with the microstructures was observed

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Not AvailableBacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae and gall midge (Orseolia oryzae) are two major constraints in rice production. In order to combine BB and GM resistance genes against two constraints, B277– SM2113 (a NIL of Samba Mahsuri) possessing BB resistance genes xa13 and Xa21 was individually crossed with two GM resistant varieties viz., Kavya possessing Gm1 (conferring HR– type resistance) and Abhaya possessing Gm4 (conferring HR+ type resistance). True F1 s from the individual crosses were again crossed to combine all 4 resistance genes. The resulting IF1 s possessing all the 4 resistance genes in heterozygous condition were selfed to generate IF2 plants. A total of 35 IF2 plants were obtained. All the 35 IF2 plants were vegetatively multiplied through tiller separation technique, genotyped with gene specific markers for all 4 resistance genes and phenotypically evaluated against both BB and gall midge. Out of 35 IF2 plants tested, a single plant showed the presence of two BB and two gall midge resistance genes in homozygous condition. Four plants carrying only BB resistance genes exhibited gall midge resistance in addition to BB resistance, while nine plants carrying only gall midge resistance genes exhibited BB resistance in addition to gall midge resistance indicating pleiotropic effect of the BB/GM resistance genes. Majority of the plants (82%) possessing both gall midge resistance genes i.e., Gm1 and Gm4 showed HR+ type resistance indicating preponderance of HR+ reaction over HR– type reaction.Not Availabl

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Not AvailableBackground: Rice, a major food crop of the world, endures many major biotic stresses like bacterial blight (BB), fungal blast (BL) and the insect Asian rice gall midge (GM) that cause significant yield losses. Progress in tagging, mapping and cloning of several resistance (R) genes against aforesaid stresses has led to marker assisted multigene introgression into elite cultivars for multiple and durable resistance. However, no detailed study has been made on possible interactions among these genes when expressed simultaneously under combined stresses. Results: Our studies monitored expression profiles of 14 defense related genes in 11 rice breeding lines derived from an elite cultivar with different combination of R genes against BB, BL and GM under single and multiple challenge. Four of the genes found implicated earlier under combined GM and BB stress were confirmed to be induced (≥ 2 fold) in stem tissue following GM infestation; while one of these, cytochrome P450 family protein, was also induced in leaf in plants challenged by either BB or BL but not together. Three of the genes highlighted earlier in plants challenged by both BB and BL were also found induced in stem under GM challenge. Pi54 the target R gene against BL was also found induced when challenged by GM. Though expression of some genes was noted to be inhibited under combined pest challenge, such effects did not result in compromise in resistance against any of the target pests. Conclusion: While R genes generally tended to respond to specific pest challenge, several of the downstream defense genes responded to multiple pest challenge either single, sequential or simultaneous, without any distinct antagonism in expression of resistance to the target pests in two of the pyramided lines RPNF05 and RPNF08.Indian Council of Agricultural Research – National Agricultural Science grant No. NASF/ABP-5009/2015-1