Search results

The microstructure was a fine-grained mixture of lamellar pearlite and proeutectoid ferrite which is found predominantly on prior austenite grain boundaries (Fig. 4 and Fig. 5).
Prior austenite grains can be identified by ferrite network along their boundaries.
According to the in-house standard, the required grain size was G ≥ 5.0, which means that the standard was met.
Nowhere were grain sizes greater than G = 5 detected.
The transition between the brittle and tough condition is controlled by a number of external and internal factors which may alter the failure mechanism in the material.

Big γ grains, almost 0.5mm wide with intergranular ferrite and acicular ferrite inside the grains could be observed in the zones with IGC.
Large austenite grains can be observed, between 1.5mm and 3.4mm, similar to the large grains in other zones of the corner.
(a) Zone of the corner with big γ columnar grains.
Steel grade CR (ºC/min) Number of samples Analytical equation.
This fact could lead to study samples with and without Nb separately, but the number of samples without Nb would be too small for any statistical study.

There are numbers of metal plastic deformation processes such as multistage hot rolling, rotational forging etc. where huge amount of strain is reached.
Gleeble-3800 in addition to the standard simulation modes allows us to realize extreme processing modes, such as high-speed deformation modes with a large number of cycles [8].
The deformation mode was: · 8 deformations, time interval between deformations is 2 s (εi=0.15) at 1100 °C, strain rate 10 s-1 for austenite grains refinement; · 12 deformations without time interval (εi=0.25) at 756 °C, strain rate 40-50 s-1.
Rudskoy: Ultrafine and nanoscale grain structure receiving using hot and warm deformation (Science and technical journal of SPbSPU #2, St.
Kolbasnikov: Austenite grain size behaviour of pipeline steel Х90 under static and dynamic recristallization conditions (XL Science week in SPbSPU: Part VI, St.Petersburg 2011)

It is judged from the SEM images that the number of pores in tool with 35%wt bond material is at the most.
The reason is obvious that the few bond material could not bond the abrasive grains sufficiently.
It can be judged from Fig.10(a) that the lapping ability of the tool with 50%wt bond material is low for the abrasive grains are almost wholly packed by the bond material.
It also can be seen from the Fig.10 (c) that the tool surface is occupied with abrasive grains, and few pores can be found.
It can be seen from Fig.10 (b) that the number of pores on the surface of tool with 35% wt bond material is most.

Table 2 Various cooling methods and heat treatment processes Sample Number Thickness[mm] HeatTemperature[°C] Holding Time[min] Cooling Method 1 3.0 1200 5 300°Cfurnace cooling 2 3.0 1200 5 Air cooling 3 3.0 1200 5 Water cooling According to Fig.1, Vickers hardness values of all points from core layer to cladding were drew as shown in Fig.2.
The composite grain grow obviously after hot treatment compared with the microstructure after hot rolling (Figure 3(a)), particularly in furnace cooling, the grain grow seriously because of the low cooling speed as shown in Figure 3.
The fine and homogeneous grain are achieved by hot-rolling and the grain across the bonding surface make the interface disappeared while a dark layer appeared between cladding and core layer reduce with the increase of cooling speed.
Table 3 Quenching and tempering process Sample Number Heat Treating Process Quenching Temperature[°C] Holding Time[ min] Tempering Temperature[°C] Holding Time[ min] 4 1010 5 200 10 5 1030 5 200 10 6 1050 5 200 10 7 1070 5 200 10 8 1030 5 150 10 9 1030 5 400 10 The hardness distributions of composite in various quenching and tempering temperatures were shown in Fig.4 and Fig.5.
(b) (a) (c) (d) (e) (f) Fig.6 Microstructure of composite in various heat treatment conditions The grains of composite cladding after quenching and tempering were homogeneous and tiny, as shown in the metallographs.

Experimental Design The design of experiments (DOE) has a major effect on the number of experiments required.
With DOE the total number of experiments required can be minimized.
Design Expert software is used as a tool to optimize the number of experiments.
°C, operating Temperature 1000oC The cutting experiments were carried out on V-55 vertical milling machine using micro grain solid carbide end mill with two flutes as shown in Fig 1.
Micro grain solid carbide end mill Fig 2.

Introduction Carbon-based materials (CBMs) are favourable for the plasma facing materials in fusion devices because of the low atomic number, favorable thermo-mechanical properties and the absence of melting.
Experimental In this study, a fine grain graphite grade, R6650 (SGL Carbon, Germany) was used as a sample for thermal shock experiments.
The nominal grain size of the original grade was around 7µm.
The laser beam spot had a diameter of 2 µm, which is smaller than the nominal grain size of the graphite grade, hence, the obtained spectra was considered to be acquired from individual graphite grains but not averaged signal over grains and binder phases.
This indicates that the graphite grains exhibit more ordered structure after the thermal shock load.

The <100> // ND surface grains nucleate more rapidly because they have the lowest interfacial energy with the surrounding atmosphere.
The surface grain size and structure is unique in pure iron and ultra low carbon steel, which display a slightly columnar monolayer of predominantly <100> oriented surface grains on top of a matrix consisting of equi-axed <111>//ND bulk grains.
The laboratory cast alloys L302 and L296 display a similar grain structure and grain size, which is confined to the surface and extends to a few microns (15-30 microns) underneath the surface.
A number of investigations have been performed on oxides and it was shown that some oxide grow predominantly by inward diffusion of oxygen (SiO2, Al2O3 and Cr2O3 in the most cases) and some by outward diffusion of cations (ZnO, MnO, FeO and Fe3O4) [14].
Also the fraction of surface metal grains that is covered by oxide is of relevance with regard to the issue of orientation selection.

The material dependent constants p, q and s describe the powers of the strain, strain rate and the grain size, respectively.
This gave an equiaxed mean linear intercept grain size of 120 mm.
Recrystallization times for the present steel are compared with other steels for a strain of 0.2 at 0.1 s-1 and a grain size of 140 mm in Fig. 8.
Confirmation experiments indicated that the power of grain size developed for carbon steels was reasonably accurate for TWIP steels, too.
Acknowledgements The authors would like to thank the European Commission for funding part of this research under grant agreement number RFSR-CT-2010-00018 and for permission to publish the results.

Ti5Si3 particles with size less than 1 μm are distributed uniformly in matrix grains as a reinforcing phase.
Ti (wt. %) Al (wt. %) Si (wt. %) Theoretical target Ti5Si3 content (wt. %/) S0* 45 36 0 0 S5 64.5 34.2 1.3 5 *SX refers to the sample number, and X is the targeted weight per cent of Ti5Si3 phase Results and Discussion In order to investigate the structure evolution of the mixture of Ti-Si-Al during the sintering, DSC is performed and shown in Fig.1.
The former offers the coarse grain sized, but the latter has the fine duplex structure of the lamellar phase of α2 (Ti3Al) and colonies equiaxed γ (TiAl) phase.
Compared with the TiAl monolithic intermetallics fabricated at the same condition (Fig. 4(a)), it can be seen that the grain size of the as fabricated composites becomes remarkably finer and distributed more uniformly, results from the effect of in situ formed Ti5Si3 with fine size.
Compared with Si free sample, the TiAl matrix was refined obviously due to the effect in situ formed Ti5Si3 particles with a grain size less than 1 μm.