Neutron Diffraction Pole Figures Research Articles

Texture monitoring in aluminium alloys: A comparison of ultrasonic and neutron diffraction measurement

Theories have been developed by several authors to calculate velocities of bulk, guided and surface waves in polycrystalline aggregates of cubic metals. These theories can be used to predict the effect of texture on ultrasonic velocity in rolled aluminium and steel sheet, provided that the effects of dislocations, second-phase particles, inclusions, etc. can be ignored. The theories predict that ultrasonic velocities will will be influenced by three orientation distribution coefficients (ODCs). The ODCs are quantitative measures of the texture in the material; in general, more than three ODC are required to completely characterize texture. Neutron diffraction pole figures can also be used to obtain the ODCs. Neutron diffraction measurements of ODC can be compared against ultrasonic values to obtain an independent check on the validity of the ultrasonic theories. In this work, the texture of thin sheets of a commercial grade aluminium alloy was measured with both ultrasonics and neutron diffraction. Several ultrasonic techniques were employed, using bulk, guided and surface waves. Both piezoelectric and electromagnetic-acoustic transducers (EMATs) were used. Quantitative measurements of texture made with different ultrasonic techniques were in good agreement. These ultrasonic measurements also agreed with neutron diffraction measurements, indicating that the dominant features of the effect of texture on wave propagation have been modelled with sufficient accuracy. The extension of the ultrasonic technique to on-line (production) monitoring of texture is considered. In particular, it appears that EMATs are the transducer of choice for on-line texture measurement of rolled sheet, since they are non-contacting.

Applications of Neutron Diffraction Pole Figure Measurements on Polycrystalline and Monocrystalline Metallic Samples. Examples From the Four‐Circle Neutron Diffractometer InJülich

Four different examples of neutron diffraction pole figure measurements are presented showing the variety of applications in metallic texture and microstructure analysis. Two examples are concerned with the study of texture effects on cold rolled titanium and warm bended α‐iron sheets. Two further examples are connected with the study of twinning laws and special orientation relationships in hexahedritic and octahedritic iron meteorites. Nishiyama–Wassermann orientations between α‐ and γ‐iron phases are experimentally confirmed.

Textur und anisotropie magnetischer werkstoffe

Magnetic and other properties of crystalline substances in many cases are anisotropic, that is, they depend on the crystal direction in which they are being measured. Hence, the corresponding property of a polycrystalline material depends on the orientation distribution or texture of the crystallites in the material. It may be isotropic or anisotropic corresponding to the specific texture present. The orientation distribution function cannot be measured directly. It can, however, be calculated from X-ray or neutron diffraction pole figures by means of a method based on generalized spherical harmonics. The anisotropy of the polycrystalline specimen can be expressed by the texture coefficients obtained and the single crystal constants in a rather simple way. A survey is given on the influence of textures on the anisotropy of different magnetic properties as well as the processes leading to the texture formation in materials.

The Development of Rolling Texture in α-Brass Determined by Neutron Diffraction

The three-dimensional orientation distribution was calculated from neutron diffraction pole figures for a copper 27.2% zinc alloy cold rolled to different degrees of deformation. The results agree qualitatively with those of other authors. There are however differences in the quantitative respect which influence the conclusions to be drawn. For rolling degrees lower than about 70% the texture exhibits an orientation tube similar to that of the copper type, but with a significantly different distribution along the tube axis. For rolling degrees larger than 70% the texture can be described by the orientation {110}〈112〉. The deformation is assumed to occur according to the Wassermann model and the Hu model respectively in these two ranges.

Cyclic Textures in Aluminium Wires

Three-dimensional orientation distribution functions were calculated from neutron diffraction pole figures of unwound cylinders taken at different distances from the centre of cold drawn Al-wires. Their features change from the axially symmetric type at the very centre of the wire towards a texture near to the rolling type at the surface. Relations between the three-dimensional function and ordinary fibre texture pole figures were used to study the dependence of the textures on certain processing variables for cold drawn as well as recrystallized wires.

The development of the rolling texture in copper measured by neutron diffraction

Three-dimensional orientation distribution functions of the crystallites in copper sheets, cold rolled to different degrees of reduction, have been determined using neutron diffraction pole figures. The main features of the textures may be represented by the orientation `tube' already described in prior publications. Two ranges of rolling reduction can be distinguished, a lower one (30 to 50%) and a higher one (70 to 95%) the texture changes of which correspond to those calculated after the Taylor theory. In an intermediate range (50 to 70%) a different deformation mechanism occurs which leads to an intermediate (001) [110] texture component. It is supposed that anisotropic hardening may have occurred in this range.