An assessment of high voltage electron microscopy (HVEM). An invited review

Dynamic failure of solids

Hydrogen embrittlement of α titanium: In situ tem studies

The relationship between stress and strain rate is often sigmoidal in superplastic materials, with a low strain rate sensitivity at low and high strain rates (regions I and III, respectively) and a high strain rate sensitivity at intermediate strain rates (region II) where the material exhibits optimal superplasticity This relationship is examined in detail, with reference both to the conflicting results reported for the Zn-22 pct Al eutectoid alloy and to the significance of the three regions of flow

The mechanical properties of superplastic materials

Creep cavitation in metals

An investigation of the nucleation of creep cavities by 1 MV electron microscopy

The compressive deformation of polycrystalline ɛ-zirconium hydride has been investigated within the temperature range 22 to ∼ 400° C and over the composition range ZrH1.71 to ZrH1.92. The observed deformation modes included slip, creation of new lamellae of different orientations to those of the main transformation lamellae, and movement of lamellar boundaries. The results are considered in terms of the contribution of these three processes to the overall deformation behaviour.

Some observations on the deformation characteristics of bulk polycrystalline zirconium hydrides

Deformation studies have been performed on bulk polycrystalline titanium hydride, of compositions between TiH1.53 and TiM,1.99, and at temperatures between −35 and 200° C. The yield stress increased with decreasing temperature and with increasing non-stoichiometric hydrogen vacancy content. The temperature dependence of the yield stress was enhanced with increasing vacancy content. Two-surface analysis of slip lines revealed that the slip plane was {1 1 1}. Strain-rate tests on TiH1.65 demonstrated a considerable strain-rate dependence of both yield and fracture characteristics. The effects of test temperature, non-stoichiometric defect concentration and strain-rate on the deformation and fracture characteristics are shown to be strongly related to hydrogen ion mobility.

Some observations on the deformation characteristics of titanium hydride

Intergranular cavitation has been observed during the superplastic deformation of a fine grain sized (1 μm) Cu-2.8% Al-1.8% Si-0.4% Co alloy when tested at temperatures ≥500° C. High voltage electron microscopy revealed that the cavities could be nucleated at twin boundary/grain boundary intersections. The maximum elongation occurs at a higher temperature than that of the maximum strain-rate sensitivity and this is explained in terms of grain-boundary migration, at the higher temperature, which restricts the cavitation process. This explanation was put forward on the basis of texture analysis which was used to study the deformation characteristics at the temperatures of maximum elongation and strain-rate sensitivity. The final fracture mode is shown to change with test temperature: (i) at 400° C no cavitation occurs and fracture is by ductile rupture, (ii) at 500 to 550° C cavitation occurs and fracture is by the interlinkage of voids by an intergranular void sheet (IVS) mechanism and (iii) at 800° C grain growth occurs and fracture occurs by the propagation and interlinkage of grain-boundary cracks along the grain boundaries.

C. J. Beevers

Papers

An investigation of the nucleation of creep cavities by 1 MV electron microscopy

Some observations on the deformation characteristics of bulk polycrystalline zirconium hydrides

Some observations on the deformation characteristics of titanium hydride

The relationship between intergranular cavitation and superplastic flow in an industrial copper base alloy

The Hot Fracture of an Industrial Copper-Base Alloy