Incipient plasticity in tungsten during nanoindentation: Dependence on surface roughness, probe radius and crystal orientation

The influence of crystallographic orientation, contact size and surface roughness effects on incipient plasticity in tungsten were investigated by nanoindentation with indenters with a range of end radius (150, 350, 720 and 2800 nm) in single crystal samples with the (100) and (111) orientations. Results for the single crystals were compared to those for a reference polycrystalline tungsten sample tested under the same conditions. Surface roughness measurements showed that the Ra surface roughness was around 2, 4, and 6 nm for the (100), (111) and polycrystalline samples respectively. A strong size effect was observed, with the stress for incipient plasticity increasing as the indenter radius decreased. The maximum shear stress approached the theoretical shear strength when W(100) was indented using the tip with the smallest radius. The higher roughness and greater dislocation density on the W(111) and polycrystalline samples contributed to yield occurring at lower stresses

Recrystallization in Al-Mn-Cr Alloys

The recrystallization behaviour of pure aluminium and three Al-1wt per cent Mn alloys containing 0.0,0.1 and o.5 per cent Cr as ternary additions has been studied at 90 per cent deformation and at 300 degree centigrade temperatures. It has been observed that Mn and Cr retard the softening process. The presence of 0.1 per cent Cr is useful in lowering the softening rates, whereas o.5 per cent Cr enhances the softening of the alloy. The results are discussed on the basis of the role of precipitate particles and dissolved solute atoms on recrystallization behaviour

Diamagnetic Susceptibilities of Some Cyclic Dialkylsilylamidoximes

810-81

The glass transition and crystallization kinetic studies on BaNaB9O15 glasses

Transparent glasses of BaNaB9O15 (BNBO) were fabricated via the conventional melt-quenching technique. The amorphous and the glassy nature of the as-quenched samples were respectively, confirmed by X-ray powder diffraction (XRD) and differential scanning calorimetry (DSC). The glass transition and crystallization parameters were evaluated under non-isothermal conditions using DSC. The correlation between the heating rate dependent glass transition and the crystallization temperatures was discussed and deduced the Kauzmann temperature for BNBO glass-plates and powdered samples. The values of the Kauzmann temperature for the plates and powdered samples were 776 K and 768 K, respectively. Approximation-free method was used to evaluate the crystallization kinetic parameters for the BNBO glass samples. The effect of the sample thickness on the crystallization kinetics of BNBO glasses was also investigated.Comment: 23 pages, 12 figure

Tempering characteristics of a Cu-AI-Ag Alloy

ALUMINIUM- BRONZES , particularly those containing 10 or more of aluminium, have a great potential as future engineering materials. Extensive rescarch is being carried out at present for the development of aluminium - bronzes. Various steps for improving the mechanical properties of these alloys have been recently reviewed.1 One possib-ility is to utilise the effect of ternary elements on mechanical properties and heat treatability of aluminium - bronzes