Enhancement in creep resistance of Ti-6Al-4V alloy due to boron addition

The addition of B, up to about 0.1 wt%, to Ti-6Al-4V (Ti64) reduces its as-cast grain and colony sizes by an order of magnitude. In this paper, the creep resistance of this alloy modified with 0.06 and 0.11 wt% B additions was investigated in the temperature range of 475-550 degrees C and compared with that of the base alloy. Conventional dead-weight creep tests as well as stress relaxation tests were employed for this purpose. Experimental results show that the B addition enhances both elevated temperature strength and creep properties of Ti64, especially at the lower end of the temperatures investigated. The steady state creep rate in the alloy with 0.11 wt% B was found to be an order of magnitude lower than that in the base alloy, and both the strain at failure as well as the time for rupture increases with the B content. These marked improvements in the creep resistance due to B addition to Ti64 were attributed primarily to the increased number of inter-phase interfaces - a direct consequence of the microstructural refinement that occurs with the B addition - that provide resistance to dislocation motion. (C) 2014 Elsevier B.V. All rights reserved

Isolation and Characterization of Vibrio parahaemolyticus in the hepatopancreas of cultured white pacific shrimp - Litopenaeus vannamei

Vibrio parahaemolyticus is the most common species among crustaceans, often causing various diseases and significant losses in aquaculture. Acute hepatopancreatic necrosis disease (AHPND) is a newly emerging shrimp disease that has severely damaged the global shrimp industry. This species of bacteria is associated with gastrointestinal illness in humans and has been implicated in foodborne disease. The present study carried out, isolation and characterization of pathogenic bacterial flora isolated from the infected hepatopancreas of vannamei, obtained from various aquafarms in Andhra Pradesh, India, on 11th June 2018. The collected samples were plated on TCBS- (Thiosulfate-Citrate-Bile salt-Sucrose) agar medium and Hi -Chrome vibrio, as described in Bergey's manual of systematic bacteriology. Isolated colonies were subjected to the following tests- microscopic examination, growth at different temperatures, growth at different NaCl concentrations, and biochemical tests. Further purity, maintenance, and propagation of purified cultures were done. The microbial culture was identified using 16s rRNA molecular technique. Phylogenetic Evolutionary analyses and distance matrix were conducted in MEGA7.In the present study, different samples were screened, a total of three green colonies (V44, V45, V46) were isolated, identified by biochemical tests and genetic identification as Vibrio parahaemolyticus. A systematic methodology has been developed to isolate and characterize Vibrio sp. from diseased shrimp and identify them by genetic analysis</jats:p