Increased efficiency of direct nanoimprinting on planar and curved bulk titanium through surface modification

In this work the direct transfer of nanopatterns into titanium is demonstrated. The nanofeatures are imprinted at room temperature using diamond stamps in a single step. We also show that the imprint properties of the titanium surface can be altered by anodisation yielding a significant reduction in the required imprint force for pattern transfer. The anodisation process is also utilised for curved titanium surfaces where a reduced imprint force is preferable to avoid sample deformation and damage. We finally demonstrate that our process can be applied directly to titanium rods

CONSTITUTIVE FLOW RELATIONS FOR AUSTENITIC STEELS DURING STRAININDUCED MARTENSITIC TRANSFORMATION

Comparison of the plastic flow properties of transforming metastable austenite, stable austenite, and martensite over a range of temperatures and strain rates allows quantitative estimates of (a) the static-hardening effect of the two-phase mixture and (b) the dynamic-softening effect of the transformation as a deformation mechanism. A constitutive relation is derived predicting the flow behavior of metastable austenite from the strain-induced transformation kinetics and the flow properties of the two separate phases

Changes in the mechanical properties and microstructure of anisotropic austenitic stainless sheet steel after uniaxial tensile test

The aim of the investigation is to study the changes in the characteristics of an austenitic sheet material X5CrNi18-10 (1.4301, AISI 304) after a plastic deformation. Samples are cut out from the sheet material at three different directions - 0°, 45° and 90° angle to the rolling direction. The changes in the mechanical properties and microstructure of the anisotropic austenitic steel are investigated by mechanical tests (uniaxial tension tests and hardness measurements) and structural analyses (optical and scanning electron microscopy, X-ray diffraction). It is established that the strain induced phase transformation of the metastable austenite to martensite during the tension tests changes the magnetic properties of the steel. It is found out that the sheet anisotropy effect on the uniform deformation, the thickness reduction and structure of the austenite sheet material is more essential for the plastic deformation behaviour than the strain-induced γ → α′ phase transformation

Hardening of pure metals by high pressure torsion: a physically-based model employing volume averaged defect evolutions

A physically based model to predict the increment of hardness and grain refinement of pure metals due to severe plastic deformation by high-pressure torsion (HPT) is proposed. The model incorporates volume-averaged thermally activated dislocation annihilation and grain boundary formation. Strengthening is caused by dislocations in the grain and by grain boundaries. The model is tested against a database containing all available reliable data on HPT-processed pure metals. It is shown that the model accurately predicts hardening and grain size of the pure metals, irrespective of crystal structure (face-centred cubic, body-centred cubic and hexagonal close packed). Measured dislocation densities also show good correlation with predictions. The influence of stacking fault energy on hardening is very weak (of the order of ?0.03 GPa per 100 J mol?1)