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The typical high-temperature ductile fracture morphology is related to both aggregation and growth of the large number of microscopic cavities and dimples.
Titanium alloy is typically designed for a moderate temperature (not exceeding 500℃), which prevents its wider use in air vehicles with high Mach numbers.
In addition, cavities are likely to form at grain boundaries, especially at triangle grain boundaries.
The Ti55 titanium alloy mentioned in this paper contains rare earth phase grains that provide both advantages and disadvantages: On one hand, they create an pinned effect to restrict growth of grains.
According to Fig. 6b, a large number of serpentine glide bands exist on walls of both large and small dimples.

For the extrusion speed of 0.2mm/s, the microstructure of extruded Mg rods was composed of equiaxed fine dynamical recrystallized (DRXed) grains and some elongated coarse un-DRXed grains.
On the one hand, higher extrusion speed not only enhances the nucleation of DRX grains but also shortens grain growth time and thus benefits to grain refinement [14,19].
The repeated number of the tensile testing specimens for every extrusion speed was three.
When the extrusion speed was increased to 4.0mm/s, as shown in Fig.1(c) and (f), the DRXed grains in the extruded high-purity Mg rod were remarkably coarsened and the elongated coarse un-DRXed grains vanished.
The following main conclusions can be drawn: (1) The microstructure of high-purity Mg rods extruded with extrusion speed of 0.2mm/s composed of equiaxed fine DRXed grains and some elongated coarse un-DRXed grains.

Hence, the grains are not held firmly in the bond.
In order to eliminate the influence of manufacturing parameters and reduce the statistical aspects of the positioning and number of the cutting grains in grinding wheels, only one grinding wheel was used for the experiments.
Small dressing overlapping ratios (1 < Ud <3) generate open macro structures on the surface of the grinding wheel and sharp cutting grains, which reduce the grinding forces through a decrease in the friction between the cutting grains and the workpiece material, whereas, closed structures with increased number of cutting edges and blunt cutting grains are the results of large dressing overlapping ratios (6 < Ud < 8).
The cutting grains are in much stronger bond in the infiltrated side of the wheel and therefore the number of pulled out grains from the bond decreases.
Thus the grains become dull before the outbreak.

The average dimensions of grains were 50nm and had high purity of 99.99%.
Nano-SiC grains must be rinsed before being put in the plating solution.
It could be clearly seen that the microstructure of the composite coating is superior to the common coating for the effect of nano-SiC grains on grain refining.
For another thing, the nano grains as the new growing point of crystal nucleus can decrease the increasing speed of crystal grain and results to the grain refining in the coatings(as is shown in Fig.1b), which improves the mechanical property of material further.
The reason lies in that when the number of nano particle begins to increase, the absorbed probability between particle and the surface of matrix will rise and the jogged amount into coatings also increases.

The failure requires necessarily local plastic strains where the number of cy-cles until fracture will be the lower the higher the plastic strain amplitude is ("low-cycle-fatigue").
S355 (220 HV) HAZ - fine grain S355 (220 HV) HAZ - coarse grain S355 (350 HV) HAZ - coarse grain S355 (350 HV) V-weld specimen local temperature Profile simulation specimen controlled resistance heating measurement homogeneous grain structure and hardness Base material S355 (180 HV) Base material S355 (180 HV) Base material S355 (180 HV) Base material S355 (180 HV) III Weld seam HAZ ∆UTh Weld seam HAZ ∆UTh T1 t Ac3 T2 T1 t Ac3 T1 t Ac3 T2T2 HAZ - fine grain S355 (220 HV) HAZ - fine grain S355 (220 HV) HAZ - fine grain S355 (220 HV) HAZ - fine grain S355 (220 HV) HAZ - coarse grain S355 (350 HV) HAZ - coarse grain S355 (350 HV) HAZ - coarse grain S355 (350 HV) HAZ - coarse grain S355 (350 HV) V-weld specimen local temperature Profile simulation specimen controlled resistance heating measurement homogeneous grain structure and hardness Figure 6: Welding simulation procedure [7,8] had been measured during
The calculated (NCM) and the observed (NC) remaining number of cycles are both referred to the number of cycles until crack initation.
Base material (left), simulated fine grain (220 HV, right) [7,9].
The method is not yet working with the same quality without any dependency on the grain structure.

• Impression close to the grain boundary – the distance between impression and grain boundary is smaller than the side of indentation impression
• Impression at the grain boundary - impression hits the grain boundary.
Hardness is the highest in area close to the grain boundary because the grain boundary contains various lattice defects which increase the hardness.
Grain boundary acts as a barrier for dislocation motion and consequently grain boundary prevents plastic deformation during indentation.
Hardness in the area close to the grain boundary is about 7 % higher than hardness inside the same grain.

There is a general consensus that the CET occurs when the moving front of columnar grains is blocked by equiaxed grains growing in the undercooled liquid ahead of this front, i.e. if the equiaxed grains are sufficient in size or number to arrest columnar grain growth.
Regardless of the blocking mechanisms, experiments and theoretical models have shown that the CET is significantly affected by the number of equiaxed grains and the nucleation undercooling.
Under grazing light, the resulting map shows the α(Ti) grains, i.e. the grains formed through peritectic reaction/transformation in the deep mushy zone of the sample, see Fig. 3a.
Grain structure of a CET sample prepared by power-down technique at a cooling rate of 30 K/min: (a) columnar and equiaxed α(Ti) grains in the vicinity of CET, (b) columnar and equiaxed β(Ti) grains in the vicinity of the CET.
It is clear that the α grain structure of the sample differs significantly from that of the primary β phase grains.

The preform was taken out of the substrate after deposition and then samples were cut from different locations of the preform as shown (with assigned number) in Fig.1.
Fig. 1 Locations of samples (with assigned number) cut from spray deposit for porosity, microstructure and hardness measurements.
The aluminum grain size is about 5-20 mm at peripheral region.
Wherever there is lead phase along the grain boundary, the width of the grain boundary increases due to the spread of lead on rolling.
The Pb phase is located mainly at the grain boundaries and the width of the grain boundary increases due to the spread of lead on rolling. 2.

Most of the available publications are devoted to ECAP, in particular to the dependence of the material properties on the number of the ECAP passes applied [15,16,17].
The average grain size was deq=300nm (Fig.2b).
The HE+ECAP combination gave a structure with the average grain size deq=327nm (Fig.2d) which was highly homogeneous with well-shaped equiaxed grains.
After subjecting it to HE, its structure became appreciably refined and contained well-shaped equiaxial grains and a small number of defects The average grain size was 200nm (Fig.3b).
The average grain size was 190nm (Fig.3c).

The scanning electron microscope (SEM) was used to observe the grain size.
The grain size was determined by averaging over the total number of grains in the SEM micrograph and found to be increased from 0.18 to 0.35 µm as the sintering temperature increased from 1200 to 1280 °C.
This is because larger-grained sample has lower concentration of grain boundaries [9].
Domain walls form harder when the grains are getting smaller.
For the PZT films, grain sizes increased with increasing Zr content.