Flow mechanisms in creep of short fibre AZ91 alloy-based composite

A comparison between the creep characteristics of an AZ91 magnesium alloy reinforced with 20 vol.% Al2O3 short fibres and an unreinforced AZ91 matrix alloy shows that the creep resistance of the reinforced material is considerably improved compared to the matrix alloy. It is suggested that the creep strengthening in the composite arises mainly from the existence of a threshold stress and the load transfer effect. The values of the threshold stress in the creep of the composite at temperatures in the range from 373 to 673 K were estimated using standard methods. It is proposed that the threshold stress arises from an attractive interaction between mobile dislocations and Mg17(Al, Zn)12 precipitates

Microstructural processes in creep of an AZ 91 magnesium-based composite and its matrix alloy

Constant stress tensile creep tests were conducted on an AZ 91–20 vol.% Al2O3 short fiber composite and on an unreinforced AZ 91 matrix alloy. The creep resistance of the reinforced material is shown to be considerably improved compared with the matrix alloy. The creep strengthening arises mainly from the effective load transfer between plastic flow in the matrix and the fibers. Microstructural investigations by TEM revealed good fiber–matrix interface bonding during creep exposure. The microstructures of the AZ 91 alloy and its composite were similar with regard to two types of β-phase precipitates; the enhanced precipitation of the Mg17 (Al, Zn)12 phase on the fibers is promoted by heterogeneous nucleation due to the Al enrichment of the matrix near to the alumina fibers

Influence of boron addition on the phase transformation, microstructure, mechanical and in-vitro cellular properties of bredigite-type coatings deposited by a spin coating technique

Doped calcium silicates, e.g. bredigite (Ca7MgSi4O16) have recently become a growing interest in biomedicine thanks to outstanding biocompatibility, bioactivity, and improved mechanical properties when compared to calcium phosphate counterparts. Here, we have produced thin bredigite-type coatings on Ti6Al4V substrate by the polyvinyl alcohol (PVA) assisted sol-gel spin-coating technique and studied the influence of boron incorporation (0.5 and 1.0 mol) on the microstructural, phase, nanomechanical, and in-vitro cellular properties of deposited coatings. Chemical and structural analysis of the coatings was thoroughly performed by Focussed Ion Beam Scanning Electron Microscope (SEM/FIB), Atomic Force Microscopy (AFM), differential thermal analysis (DTA-TG), X-ray diffraction (XRD), and Fourier-Transform Infrared spectroscopy (FTIR), while the nanomechanical properties were evaluated by nanoindentation and nanoscratch tests. Overall, all deposited films were smooth and porous composed of ~25–50 nm nanoparticles. The boron incorporation increased the coating thickness as a result of PVA interaction with borate ions. The nanomechanical properties (Young’s modulus, nanohardness, critical load for cracking) decreased by the boron addition as a result of decreasing the strength of grain boundaries between the nanoparticles. The in-vitro contact cytotoxicity testing revealed high proliferation of the osteoblast cells in all coatings giving the potential of application in orthopedics

Reduction of the extent of intercrystalline creep failure of copper after applying high hydrostatic pressure at room temperature

28.00; Translated from Czech. (Kovove Mater. 1989 v. 27(4) p. 504-518)Available from British Library Document Supply Centre- DSC:9023.19(VR-Trans--4414)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Influence of Long-term Annealing and Hot Bending on Creep of P92 Pipe

This work is focused on the creep behaviour of the thick-walled hot bended P92 pipe, with an outer diameter of 350 mm and wall thickness of 39 mm, in its different parts, namely in straight parts and bends. Selected creep specimens machined from axial section of pipe were thermally aged at 650°C to simulate microstructure degradation typical for long-term service conditions. Subsequent tensile creep tests at constant load were performed at 600°C under 140 MPa and creep behaviour of various structure states was compared. Microstructure was investigated by scanning electron microscopy equipped with electron backscatter diffraction. It was found that ageing at 650°C for 10⁴ h caused the significant reduction of creep resistance down to about 10% of initial state and an additional slight reduction of creep resistance after longer ageing for 2×10⁴ h. Further, creep behaviour was significantly influenced by specimen position in the extrados and intrados parts of bends. Microstructure investigation revealed that long-term annealing has negligible effect on high-angle grain boundary spacing and misorientation. By contrast, creep deformation of long-term annealed specimens led to significant decreasing in high-angle grain boundary spacing and caused a change in the misorientation distribution of boundaries

Proteogenomic refinement of the Neomegalonema perideroedesT genome annotation

Neomegalonema perideroedes (formerly Meganema perideroedes) str. G1 is the type strain and only described isolate of the genus Neomegalonema (formerly Meganema) which belongs to the Alphaproteobacteria. N. perideroedes is distinguished by the ability to accumulate high amounts of polyhydroxyalkanoates and has been associated with bulking problems in wastewater treatment plants due to its filamentous morphology. In 2013, its genome was sequenced as part of the Genomic Encyclopedia of Bacteria and Archaea (GEBA), which aims to improve the sequencing coverage of the poorly represented regions of the bacterial and archaeal branches of the tree of life. As N. perideroedes str. G1 is relatively distantly related to well described species—being the only sequenced member of its proposed family—the in silico prediction of genes by nucleotide homology to reference genes might be less reliable. Here, a proteomic dataset for the refinement of the N. perideroedes genome annotations is generated which clearly indicates the shortcomings of high-throughput in silico genome annotation