Grain excretion by goats fed whole or processed cereals with various roughages

Despite cereal grains being grown on 5 continents where goats are kept, there is little information on the excretion of whole cereal grains when fed to goats. We determined the effects of various dietary treatments on whole grain and starch loss in the faeces of Angora goats. In Experiment 1 there were 4 replicates of the factorial design: (a) 2 grain types (barley, oats); (b) whole grain or processing (milled barley or rolled oats); (c) 2 roughage qualities (Persian clover hay, barley straw); and (d) 2 feeding levels (level 1, 150 g/d of grain, 250 g/d of roughage; level 2, 250 g/d of grain, ad libitum roughage). In Experiment 2, which immediately followed Experiment 1, and aimed to detect carry over effects of previous feeding of barley straw and grain processing, feed levels were either 650 g/d grain or 400 g/d grain with 550 g/d Persian clover hay. Data were analysed by ANOVA. In Experiment 1, processing had no effect on digestible dry matter intake. The number of whole grains lost per 100 g of fresh faeces and whole grains loss as the % of grain dry matter intake were affected by an interaction between processing and roughage quality. Whole grain fed with Persian clover hay had greater grain loss than all other diets. Whole grain loss was greater with whole grain than with processed grain. Level of feeding had no effects on grain loss. In Experiment 2, more whole grains were lost in fresh faeces when fed with Persian clover hay than when fed without hay, an effect of previous feeding with barley straw reduced whole grain excretion, and more barley grains were lost than oat grain. Faecal starch was affected, with higher levels when whole barley grain was fed, particularly with Persian clover hay, or when previously fed barley straw at a high level. Feeding grain at 650 g/d did not increase grain or starch excretion. Whole grains represented a small loss of grain dry matter intake in faeces, averaging 0.8% with a maximum recorded of 2.6%. Faecal concentration of the whole grains may be altered by grain size and the digestibility of the roughage component of the diet. In this study an additional cost of 3% for processing grains would not have provided economic benefits.

Grain boundary segregation in Fe-Mn-C twinning-induced plasticity steels studied by correlative electron backscatter diffraction and atom probe tomography

We report on the characterization of grain boundary (GB) segregation in an Fe-28Mn-0.3C (wt.%) twinning-induced plasticity (TWIP) steel. After recrystallization of this steel for 24 h at 700 °C, ∼50% general grain boundaries (GBs) and ∼35% Σ3 annealing twin boundaries were observed (others were high-order Σ and low-angle GBs). The segregation of B, C and P and traces of Si and Cu were detected at the general GB by atom probe tomography (APT) and quantified using ladder diagrams. In the case of the Σ3 coherent annealing twin, it was necessary to first locate the position of the boundary by density analysis of the atom probe data, then small amounts of B, Si and P segregation and, surprisingly, depletion of C were detected. The concentration of Mn was constant across the interface for both boundary types. The depletion of C at the annealing twin is explained by a local change in the stacking sequence at the boundary, creating a local hexagonal close-packed structure with low C solubility. This finding raises the question of whether segregation/depletion also occurs at Σ3 deformation twin boundaries in high-Mn TWIP steels. Consequently, a previously published APT dataset of the Fe-22Mn-0.6C alloy system, containing a high density of deformation twins due to 30% tensile deformation at room temperature, was reinvestigated using the same analysis routine as for the annealing twin. Although crystallographically identical to the annealing twin, no evidence of segregation or depletion was found at the deformation twins, owing to the lack of mobility of solutes during twin formation at room temperature.

The five-parameter grain boundary character and energy distributions of a fully austenitic high-manganese steel using three dimensional data

The three-dimensional interfacial grain boundary network in a fully austenitic high-manganese steel was studied as a function of all five macroscopic crystallographic parameters (i.e. lattice misorientation and grain boundary plane normal) using electron backscattering diffraction mapping in conjunction with focused ion beam serial sectioning. The relative grain boundary area and energy distributions were strongly influenced by both the grain boundary plane orientation and the lattice misorientation. Grain boundaries terminated by (1 1 1) plane orientations revealed relatively higher populations and lower energies compared with other boundaries. The most frequently observed grain boundaries were {1 1 1} symmetric twist boundaries with the Σ3 misorientation, which also had the lowest energy. On average, the relative areas of different grain boundary types were inversely correlated to their energies. A comparison between the current result and previously reported observations (e.g. high-purity Ni) revealed that polycrystals with the same atomic structure (e.g. face-centered cubic) have very similar grain boundary character and energy distributions. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ultrafine grain formation in a Ti-6Al-4V alloy by thermomechanical processing of a martensitic microstructure

In the current study, ultrafine equiaxed grains with a size of 150 to 800 nm were successfully produced in a Ti-6Al-4V alloy through thermomechanical processing of a martensitic starting microstructure. This was achieved through a novel mechanism of grain refinement consisting of several concurrent processes. This involves the development of substructure in the lath interiors at an early stage of deformation, which progressed into small high-angle segments with increasing strain. Consequently, the microstructure was gradually transformed to an equiaxed ultrafine grained structure, mostly surrounded by high-angle grain boundaries, through continuous dynamic recrystallization. Simultaneously, the supersaturated martensite was decomposed during deformation, leading to the progressive formation of beta phase, mainly nucleated on the intervariant lath boundaries.

Time and spatial resolution of slip and twinning in a grain embedded within a magnesium polycrystal

Plastic yielding in magnesium alloys frequently involves the initiation of both slip and twinning events. A proper understanding of the phenomenon at the grain level requires knowledge of how these two mechanisms progress and interact over both time and space and what the local resolved stresses are. To date, simultaneous collection of such information has not been achievable. To address this shortfall, we have developed a modified Laue based in situ micro X-ray diffraction technique with an unprecedented combination of time and spatial resolution. A ten-fold reduction in data collection times is realized by the refinement of rapid polychromatic Laue "single-shot" mapping. From single Laue patterns, we extract grain depth information, detect onset of yielding and achieve 2 × 10-4 lattice strain resolution. The technique is employed to examine yielding and twinning in a magnesium grain embedded ∼200 μm below the sample surface. We examine 13 time steps and reveal the following behaviour: initial onset of basal slip, subsequent onset of twinning, development of further accommodation slip and evolution of twin shape and size; along with the corresponding values of local resolved shear stresses. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Acceleration of the super bainite transformation through a coarse austenite grain size

The effect of austenite grain size on the kinetics of the isothermal bainitic transformation in a high-carbon super-bainitic steel was investigated. Experimental results showed that the transformation of super bainite was accelerated by a coarse austenite grain size. This is because while coarse austenite grains provide less nucleation sites, it is beneficial for bainite sheaf growth. Meanwhile, there is a critical austenite grain size below which there is a distinct grain size effect and above which it is not evident. © 2014 Elsevier B.V.