The deformation of structural alloys presents problems for power plants and aerospace applications due to the demand for elevated temperatures for higher efficiencies and reductions in greenhouse gas emissions. The materials used in such applications experience harsh environments which may lead to deformation and failure of critical components. To avoid such catastrophic failures and also increase efficiency, future designs must utilise novel/improved alloy systems with enhanced temperature capability. In recognising this issue, a detailed understanding of creep is essential for the success of these designs by ensuring components do not experience excessive deformation which may ultimately lead to failure. To achieve this, a variety of parametric methods have been developed to quantify creep and creep fracture in high temperature applications. This study reviews a number of well-known traditionally employed creep lifing methods with some more recent approaches also included. The first section of this paper focuses on predicting the long-term creep rupture properties which is an area of interest for the power generation sector. The second section looks at pre-defined strains and the re-production of full creep curves based on available data which is pertinent to the aerospace industry where components are replaced before failure.

Observed differences between measured and calculated elastic constants for Ti 3 SiC 2 are investigated using Density Functional Theory and Inelastic Neutron Scattering. The agreement between the calculated lattice dynamics and the dynamics measured by inelastic neutron scattering is considered good except at energies below~20 meV where discrepancies suggest anharmonic potentials. This suggestion is confirmed by Density Functional Theory-Molecular Dynamics simulation which shows multiple site occupancy of the Si atoms within the basal plane at finite temperature and produces a calculated inelastic spectrum in better agreement with the measured spectrum in the low-energy region. The highly anharmonic potential energy surface of the Si atoms offers an explanation for the failure of elastic constants, calculated based on the harmonic approximation, to agree with initial experimental measurements.R. Koc-contributing editor Manuscript No. 33332.

This paper details the development and assessment of a new empirical creep model that belongs to the limited ranks of models reproducing full creep curves. The important features of the model are that it is fully standardised and is universally applicable. By standardising, the user no longer chooses functions but rather fits one set of constants only. Testing it on 7 contrasting materials, reproducing 181 creep curves we demonstrate its universality. New model and Theta Projection curves are compared to one another using an assessment tool developed within this paper.

This letter explores issues surrounding region splitting, a current technique used to improve creep life predictions. The history of the technique is discussed briefly and its current implementation by major research groups described in more detail. An example of novel or non-traditional region splitting is also explored with its first known application to nano-creep. The issues surrounding region splitting when considered as an industry practice are also briefly discussed. The purpose of this letter is to explicitly discuss region splitting as a creep lifing technique and identify the current and future issues researchers and industry may face when implementing this powerful technique.

With the drive towards cost‐effective routes for the manufacture of engineering components, flow forming technologies are now under consideration for the production of structural axisymmetric geometries such as tubes and cones. This near net shape process is known to offer improvements in material utilisation when compared with traditional processes where substantial final machining is required. The microstructure, evolved as a result of the flow forming process together with subsequent heat treatments, will govern associated mechanical properties. Laboratory measurements of the structure‐property relationships of flow formed material can be problematic, mainly because of the restrictions imposed on the extraction of conventional specimen geometries since most of the finished tubular or cone structures will contain thin and curved walls. The development of a suitable specimen design and associated test technique for the measurement of fatigue crack growth rates at room and elevated temperatures is presented. Data obtained from flow formed Inconel 718 (IN 718) will be compared with specimens of the exact same geometry but machined from conventionally forged IN 718 stock. This allowed for validation of the novel flow formed test in addition to an assessment of the damage tolerance of the flow formed variant. The intimate relationship between local microstructure and fracture mechanisms will be described.

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The magnitude of the single‐crystal elastic constant c44 in the MAX phase Ti3SiC2 is under debate. In this paper, estimates for the magnitude of c44 for MAX phases Ti3AlC2 and Ti3SiC2 are determined from a partially oriented polycrystalline sample via coherent inelastic neutron scattering. The largely quasi‐isotropic nature of these Mn+1AXn phase elastic constants as previously predicted by density functional theory calculations is confirmed experimentally for Ti3AlC2 to be c44=115.3 ± 30.7 GPa. In contrast, Ti3SiC2 is confirmed to be shear stiff with c44=402.7 ± 78.3 GPa supporting results obtained by earlier elastic neutron diffraction experiments.

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