Abstract: The deformation ability of metals and the mechanic characteristics of metal parts are
closely related to the material’s microstructure and grain size, so it’s important to study the simulation
techniques of microstructure evolution. Common microstructure simulation techniques include
digital simulation and graphic simulation. This paper firstly introduced the simulation techniques of
microstructure, and then focused on the graphic simulation technique that can directly show grain
boundary network’s evolution process. It then built a Monte Carlo model of the grain growth during
super plastic deformation, and implemented the graphic illustration of grain growth using Visual
Studio software. The result matched well with the experimental outcome, which proved the usability
of the technique
Abstract: In this paper, a simplified cellular automaton (CA) model was proposed for modeling the
evolution of microstructure in solidification process of AZ91D magnesium alloy. Since the
calculation time was significantly reduced, it might be used to predict the microstructure field of a real
Mg component after solidification. The stochastic nucleation, competitive growth processes of many
grains with various crystallographic orientations and the formation of eutectic structure were also
taken into account. Furthermore, step castings were poured with sand and permanent molds and
metallographic experiments were carried out for validating the developed models. It was shown that
the simulation results are in good agreement with those obtained in the experiments.
Abstract: Slow shot velocity and its acceleration phase in the shot sleeve have great influence on the
flow pattern of the liquid metal in the shot sleeve. In this paper, a three-dimensional model based on
the SOLA-VOF algorithm was developed and used to simulate the flow of melt in the shot sleeve. The
mathematical model was verified by water analog experiments with constant plunger velocities.
Based on numerical simulation results, the influences of the plunger acceleration on the wave profile
of the liquid metal in the shot sleeve under different fill ratios and sleeve diameters were investigated.
The results indicated that in order to avoid air entrapment in the shot sleeve, the optimal acceleration
value to the critical slow shot velocity increases with the increase of the fill ratio, and the range of
suitable acceleration becomes wider as well. With the same fill ratio, the value of suitable acceleration
rises as the plunger diameter increases.
Abstract: The micro structural evolution and the mechanism of recrystallization grain growth were
studied during re-aging process in Cu-Ni-Si alloy containing finely pre-aging δ-Ni2Si precipitates
using computer simulations based on a diffuse-interface phase-field kinetic model. In this model, the
temporal evolution of the spatially dependent field variables is determined by numerically solving the
time-dependent Ginzburg-Landau (TDGL) equations for the structural variables. The simulation
results quantify the effects of the precipitation on recrystallization. It is shown that the finely
dispersed pre-aging δ-Ni2Si precipitates exert a strong pinning effect on the recrystallization grain
boundaries. The recrystallization grain growth for r = 3 fa = 0.015 can be described as R =1.04∗t 0.33
at the beginning, followed by a gradual transition to growth stagnation. The final grain size follows a
Zener type relation
lim 0.49 1.41
for 0.01 ≤ fa ≤ 0.21 and r = 2.5 or 3.
Abstract: In this paper we present an anisotropic compaction model based on a generic
modeling framework. The model is a generalization of Hill’s anisotropic model to
compressible materials and reduces to a Cam-clay type model in the isotropic limit. The
model has been calibrated using experimental data for a commercial steel powder
obtained from a computer controlled triaxial cell in which the yield surface was probed
following loading along different paths in stress and strain space. Closed-form
analytical expressions are presented for the yield surface as a function of the inelastic
strain. The model has been implemented in the general purpose finite element code
ABAQUS. Simulations are presented which explore the effect of a detailed structure of
the constitutive law on the compaction response.
Abstract: Material behaviors of anisotropy and rate sensitivity affect cold ring rolling greatly. So, a
self-developed incremental model of rate dependent crystal plasticity (RDCP) is utilized to forecast
the deformation characteristics of this forming process based on a 3D FE model under
ABAQUS/Explicit environment. The results show that the model of RDCP captures material
behaviors of anisotropy and rate sensitivity better in this forming process by the comparison with the
model of J2 plasticity; with the decrease of rate sensitivity coefficient, the forming process becomes
more unstable with smaller rolling force and growth in ring radial direction; with the increase of feed
rate of idle roll, the deformation of ring becomes more even while the rolling force becomes larger.
Abstract: It is commonly considered that the character of atomizing gas-flowing field would affect
breaking method of molten metal, liquid droplet size and mass distribution. It is one of the important
factors which determine the microstructure and metallurgical quality of products. In this paper, three
types of atomizers were designed and Pitot tube was used to investigate the steady state gas flow field
generated by a close-coupled spray deposition atomizer. Through the study of atomization gas
velocity distribution by simulation and experiment, the construction and gas flow dynamical property
were introduced in this paper.
Abstract: A new expression for the chemical bond in perovskite-type oxides is proposed based on the
atomization energy concept. The atomization energies, Eo for oxygen atom and EM for metal
atom in each oxide are evaluated theoretically using the energy density analysis of the total energy,
and the 9EO vs. 9EM diagram called atomization energy diagram, is constructed. Every oxide can
be located on the atomization energy diagram, although there are significant differences in the
nature of the chemical bond among the oxides.
Abstract: Two dimensional simulations of discrete dislocation dynamics were carried out to clarify a
shielding effect due to dislocations at a crack tip. The configuration of dislocations around the crack
tip was calculated under the conditions of mode I tensile load at high temperatures. The stress field
around the crack tip due to dislocations was found to be compressive, accommodating mode I stress
intensity at the crack tip. In order to experimentally confirm the stress accommodation, infrared
photoelastic observation was also performed in a specimen pre-deformed at high temperatures. The
experimental result is in good agreement with a simulated infrared photoelastic image derived from
the stress field calculated.