Search results

It was established that upon SPD a number and a size of aluminides decrease with increasing a degree of deformation.
The number of anvil revolutions was varied from 0.5 to 10 (equivalent to logarithmic true train e = 3.8-6.7).
The matrix phase has grains with size about 5 µm.
Matrix lattice parameter and the relative level of matrix microstresses (a) and the hardness (b) of the Al-2% Fe alloy depending on the number of revolutions It was show that upon annealing at temperatures below 250 o C (for Al-Zr alloy) and 300o C (for AlFe and Al-Cr alloys) the grains do not grow above 300 nm.
The most intense grain growth begins at temperatures above 350 oC and 450 o C the grain size reaches 1.5 µm.

A large number of intragranular pores and a small number of overall pores was observed in Ca-PSZ, resulting in this material having the lowest bulk density.
The grain size of Ca-PSZ is non-uniform, and most of the grains, those with an average grain diameter of around 6 μm, are densely packed, however, there are also some irregular grains, with an average grain diameter of around 10 μm, and a large number of pores, resulting in the low bulk density of the material.
The average grain size of Mg-PSZ is larger, with an average grain diameter of around 7 μm, and the grain shape is irregular.
Y-PSZ has a uniform grain size, with an average grain diameter of around 5 μm, and sharp edges.
No abnormal grain growth was observed for the sample, the grain bonding is compact, and a small number of pores exist in the material.

Alloy development and grain size control
After isothermal forging the grain size is reduced to about 120µm because the borides formed on casting are broken up and pin grain boundaries during recystallisation and during grain growth.
The grain size found in ingots of Ti46Al8Nb1B is about 150µm and in this case appropriate thermomechanical processing can lead to grain refinement to produce grains of about 100µm [5].
This type of microstructure is developed because the massive gamma is full of crystal defects which increase the number of potential sites for the precipitation of alpha which can precipitate on all four {111} planes in the gamma, yielding the complex type of microstructure shown in Figure 2.
It is likely that pre-yield cracking will not be an issue in this type of alloy since it is very fine grained, with a grain size of about 10µm.

A zone of fine grains is located next to the columnar ones, and at an interface with the bronze matrix much coarser grains are seen.
The Nb3Sn grains in continuous diffusion layers get larger by a factor of 1.5 and the grain size scattering broadens (Fig. 3, Table 1).
As seen from Table 1, Ti does not result in grain refinement of superconducting layers, which we already observed in a number of previous studies [8,11,16].
Parameters of Nb3Sn grain size distribution No.
There is a zone of columnar grains adjacent to the residual Nb, a zone of fine equiaxed grains and some amount of coarser grains at an interface with the bronze matrix, which is typical of bronze-processed wires.

All these techniques resulted in pronounced grain refinement.
Currently, austenitic stainless steels are widely used for a number of structural applications [3].
This microstructure is composed of alternating nano-scale austenite and matrensite grains.
Only austenitic nano-scale grains with an average size of ~23 nm evolve during HPT (Fig. 1c).
Langdon, Twenty-five years of ultrafine-grained materials: Achieving exceptional properties through grain refinement.

Sintered SiAlONs are of two types with different microstructural features [22, 25]: (1) β-sialon grains plus glass, (2) β sialon grains plus crystalline YAG.
As the grain boundary composition changes, the aspect ratios of β grains vary and grain coarsening also occurs as sintering time or temperature is increased.
Effects of Grain Boundary Glass on Properties.
Grain boundary chemistry affects interfacial bond strengths.
Other practical advantages of high toughness values (KIc = 7-10 MPa.m1/2) include resistance to machining damage and improved fatigue behavior, KIc increasing with the volume fraction of elongated grains and proportional to (grain size) 1/2, an effect due to "crack wake mechanisms", such as crack bridging, grain rotation and grain pullout.

Grain size of NiO and SDC could be estimated from the diffraction peaks according to Scherrer equation expressed as[5]:
Table 1 Cell parameter and grain size of NiO and SDC Sample Cell parameters Volume Average grain size A(×10-1nm) V(×10-3nm3) D(nm) NiO SDC NiO SDC NiO SDC NiO400-SDC400 3.965 5.427 62.4 159.9 30.1 15.6 NiO600-SDC600 3.969 5.428 62.6 160.0 56.5 19.7 NiO800-SDC800 3.969 5.430 62.6 160.1 63.4 44.8 The grain size of NiO powders calcined at 400, 600 and 800℃ is 30.1, 56.5 and 63.4nm, and the size of SDC is 15.6, 19.7 and 44.8 nm.
As shown in Table 1, there is grain growth with calcining temperatures from XRD lines broadening.
Thus, the high performance of this anode seems to be attributable to the increase in the number of active sites at the boundary between Ni, SDC and H2 gas.
As shown schematically, the Ni grains form a skeleton with well-connected SDC grains finely distributed over the Ni grains surfaces.

The results indicated that the fracture of the rod is induced by the unqualified chemical composition: a large number of inclusions which distribute in grain boundaries reduce the material plasticity and toughness, and eventually cause fracture.
The segregation of s along grain boundaries can weaken the gain boundary strength and induce the embrittlement eventually.
A large number of inclusions can be observed homogeneously distributed in matrix from Fig.4.
The results indicated that matrix metallographic structure is ferrite and pearlite, and the grade of grain size is 7-9, whether horizontal or vertical section.
(3)A large number of inclusions which distribute in grain boundaries reduce the material plasticity and toughness, and eventually cause fracture.

�-fibre grains (ND-fibre grains) are, in general terms, more fragmented than �-fibre grains (RD-fibre grains).
This technique enables the orientation of deformation bands, the misorientation across them, the orientation of the new recrystallized grains and the misorientation of those grains with the adjacent matrix grains to be determined.
In zones 3 and 4 a great number of low angle boundaries (<15°) parallel to RD originate, which intersect with the microbands running perpendicular, as can be seen in the image quality map.
The orientations of the recrystallized grains numbered from 1 to 9 in the figure and the misorientation angle/axis with respect to neighboring zones are gathered in Fig. 3-c.
Conf. on Rex. and Grain Growth, Trans.

The grain boundary suffers severe corrosion, moreover, a number of grains peel off, i.e. the dark spots in Fig.2(a).
It is because the strength that makes grains interconnected decrease sharply after the grain boundary is eroded, leading to great separation of grains.
However, the number of IGC signals is much more than that in [3].
Therefore, it is very possible that different testing methods result in different number of AE signals.
Xu [3] did not explore the AE source due to the low AE activity and poor numbers of signals.