Search results

The effects of introducing second phase particles have been studied for ultrafine grained plain C-Mn steels [10] and for an ultrafine grained Cu-Cr-Zr alloy [11].
In the latter case, accumulative roll bonding (ARB) followed by aging was employed to produce a microstructure consisting of ultrafine elongated grains and Cu3Zr precipitates <10 nm at the grain boundaries and inside the grains.
They reported that no precipitates exist in the ultrafine grains and at grain boundaries of the as-ARB processed specimen.
The large number of Si particles precipitated at the lamellar boundaries in the present nanostructured Al-1% Si alloy must have a strong effect on stabilizing the lamellar structure, which explains the fact that the microstructure is rather stable during annealing although the matrix is super pure [12].
Effect of aging treatment on ultra-fine grains and Si-phase in Al-0.5%Si alloy fabricated by ARB process, Mater.

The strength and formability of aluminum alloys depend on the distribution and scale of precipitating phases, on the grain size and grain orientation distribution, on the distribution and scale of flaws, and on the presence of residual stresses.
Thus it is useful to have detailed quantitative data on the crystal structures and volume fractions of phases that form during thermomechanical treatment, on the kinetics of solid state reactions, on the distribution of grain orientations, and on the stresses that develop during mechanical testing and forming.
Neutron diffraction provides bulk-averaged lattice strains for several components of the texture as a function of load, which provides insight into the interaction between grains through analytical and finite element models of polycrystal plasticity [4, 5].
Unlike X-rays, for which attenuation increases systematically with atomic number, neutron attenuation varies somewhat randomly across the periodic table.
Neutrons are thus often sensitive to small differences in atomic number, which allows heterogeneities to be imaged that would not be visible in X-ray radiographs.

A micromechanical model was developed to account for the particular microtexture of upper bainite in low alloy steels, i.e. the non-random spatial distribution of variants within a given former austenite grain.
Disorientation angle histograms between bainite variants within a given parent austenite grain systematically show a non-random distribution of variant boundaries.
Numbering of variants and corresponding axis-angle pairs with respect to variant 1, for p2 = {11}γ, g2_conv = 0.1302, p2 = {311}γ, h = {557}γ.
Calculations were performed in the frame of the parent austenite grain with no external stress.
The term was added for austenite in Eq. (4) to ensure that convergence occurred for a similar number of iterations in all phases.

Table 1 Selection of parameters and their dimensions Number Parameter Unit Dimension 1 Pressure drop ΔP Pa ML-1T-2 2 Inlet pressure P Pa ML-1T-2 3 The length of the separation board LC mm L 4 The height of the chamber H mm L 5 The lengthof the chamber L mm L (1) (2) (3) Three groups of π above-mentioned show that the relation of three group parameters, which can be used to guide the model design for model experiment.
Table 2 Values of independent variable parameters Number Parameter Unit Selected values of independent variable 1 Inlet pressure P Pa -38.4,-76.2,-104.6,-129.5,-153 2 The length of the separation board LC mm 750,850,950,1050,1150 3 The height of the chamber H mm 850,940,1000,1060,1120 4 The length of the chamber L mm 1700,1900,2100,2300,2500 Experimental Project
The experimental grain is offfered by Xiangfang Farm.
Engng Res(1998) [4] Enchen Jiang: A Stripping Unit and Pneumatic Conveying System for Grain Harvesting.
Grain harvesting: submitted to Agricultural Services Div (1994) [6] Hao, Laxton Y.

These reinforced phases can pin the grain boundaries and hinder the grain boundary sliding so to increase the high temperature performances.
With the increase of grinding durations, grain sizes and lattice parameters of Al and Ti powders change correspondingly.
As shown by the SEM images in which the bright spots are Ti and gray spots are Al, small Ti grains embed in Al matrix.
For that after the particle grain size decreases to nano scale, the dislocations in small grains are difficult to store inside the grain and easy to slip to the grain boundary, resulting the obvious restard of grain size descent rate.
Under the action of milling, a great number of lattice defects are introduced in the powders, which decrease the atomic diffusion resistance, increase the energy stored by powders and shorten the mutual diffusion distance between Al and Ti atoms.

Moreover saturation curve of C % could be reached after 1 min SMAT, thus less time needed for complete area coverage with large number of 65 balls used.
Conclusions - Imposed freq. of 40 Hz lower than starting limits of 50 Hz-SMAT [6] causes Al grains rotation due to less plastic than elastic deformation and high angle grain boundaries.
Thus grain rotation is preferable than fragmentation proved by XRD textured Al (113) planes parallel to sample's surface due to majority of grains take the same orientation
- At 50 Hz-SMAT small angle grain boundaries form due to increase of grain refining.
Rohrer, Habits of Grains in Dense Polycrystalline Solids, J.

After aging samples were mechanically ground using emery paper from mesh number 280 to 3000 and polished till mirror like surface.
Other kind of phase is a lamellar structure which only nucleated on the grain boundaries.
Figure 6(b) showed the crack propagation site in high C-Ti alloy is on the grain boundary.
Here crack on grain boundary initiated due to eta phases.
However, due to the excessive formation of eta phases on the grain boundaries of high C-Ti alloy as shown in figure 2(d) propagate the crack through the grain boundaries figure 5(d).

Based on different sizes and different speed of grain, loading, cutting and unloading process are simulated by finite element, guide surface stress distribution and deformation condition are studied in the guide rail pair wear process.
Grains are simplified for round in geometric model, profile radiuses are R, and take different radius R to test.
Due to the grain of guide rail pair are all hard particles, its deformation do not be considered, And according to the content which this paper tries to study, so suppose the abrasive look for the rigid body, be ground guide material for elastic-plastic soft body[3].
Table 3 Central composite experimental data Test number Experiment Type Results V[m/s] R[mm] U[mm] S[MPa] 1 0.243918 0.013536 cube point 1.002e-02 1.453e+03 2 0.243918 0.006464 9.957e-03 1.647e+03 3 0.456082 0.013536 9.998e-03 1.548e+03 4 0.456082 0.006464 1.001e-02 1.527e+03 5 0.350000 0.010000 central point 1.010e-02 1.501e+03 6 0.200000 0.010000 axial point 9.889e-03 1.575e+03 7 0.500000 0.010000 1.001e-02 1.532e+03 8 0.350000 0.005000 1.003e-02 1.714e+03 9 0.350000 0.015000 1.006e-02 1.525e+03 Finite Element Model.

(2) Large numbers of rotating components, such as bucket wheel, reamer and sand pump, they are all worn seriously, which need frequent change, large amount of maintenance, high operating costs and complicated management equipments
Table 1 Initial conditions Dariable Domain Description rho_water 1000[kg·m-3] Density of water nu_water 1.51×10-3[Pa·s] Viscosity r_grain 1[mm] Radius V_grain 4/3·pi·r_grain3 Volume rho_grain 2900[kg·m3] Density of grain m_grain V_grain·rho_grain Mass F_g -m_grain·g_const Gravity Fig.1 Geometry, control equations and boundary conditions of the model The general equations of laminar flow are shown in (2) and (3): (2) (3) In the simulation process, the partial differential equations are coupled to describe the movement of the particles, as shown in Table 2.
Table 2 The global equations Name F(u,ut,utt,t) Initial value(u) Initial value(ut) X Xt-Xdot 0 0 Xdot Xdott-(F_z+F_g)/m_grain 0 0 In the sediment sink process of simulation, the points every 0.025s are taken to calculate, in the end, 40 points are taken.

A linear intercept method for each specimen was used to estimate the average grain size.
The microstructural variables, including the grain length, aspect ratio and volume fraction of α phase, were obtained.
%H，Td= 700°C，ε& = 8.3×10 -2s-1 The trained models were used for prediction of grain length l, volume fraction of the original α phase Vα and aspect ratio γ.
The calculated grain length, volume fraction of the original α phase and aspect ratio are found to be highly satisfactory in comparison with the experimental results.
Except prediction value of grain length, the relative errors of all models are below 10%.