Abstract: Copper powders with very dense, uniform silver coating layer were prepared by electroless
plating method in aqueous system at room temperature. Silver-copper composite powders were
obtained by strictly controlling the activation and complexing process variables such as
NH4OH/(NH4)2SO4 molar ratio, tartrate concentration, and feeding rate of silver ion solution. The
mechanism of composite powders formation and their characteristics were discussed. It is noted that
completely cleansing the oxide layers and protecting the copper particles surface from hydrolysis
are key factors to obtain high quality Ag-Cu composite powders.
Abstract: Tensile tests of epoxy molding compounds were carried out using specimens composed of
epoxy molding compounds which are transfer molded and post cured. The mechanical characteristics
of the epoxy molding compounds change significantly due to changes in temperature and strain rate.
In addition, the effect of nonlinear viscosity is large in both elastic and plastic regions. The
characteristics of the visco-elastic-plastic behaviors of the epoxy molding compounds were examined.
The behavior characteristics of the epoxy molding compounds during loading and unloading were
shown in detail.
Abstract: Gradient-dependent plasticity where a characteristic length is involved to consider the
microstructural effect (interactions and interplaying among microstructures due to the heterogeneous
texture) is introduced into Johnson-Cook model considering the effects of strain-hardening, thermal
softening and strain rate sensitivity. Effects of initial static yield stress, strain-hardening coefficient
and exponent, strain-rate and thermal-softening parameters on the occurrence of phase
transformation and the thickness of phase transformed adiabatic shear band (ASB) in deformed ASB
are numerically investigated. Higher initial static yield stress, strain-hardening coefficient, strain-rate
parameter and lower strain-hardening exponent lead to earlier occurrence of phase transformation
(lower plastic shear strain). Effect of thermal-softening parameter on plastic shear strain
corresponding to the onset of phase transformation is not monotonous. Transformed ASB is located
at the center of deformed ASB since the position has higher temperature exceeding the temperature of
phase transformation. The thickness of transformed ASB increases with decreasing flow shear stress
and the increasing tendency becomes slow. For the same flow shear stress, the thickness of
transformed ASB is wider for higher initial static yield stress, strain-hardening coefficient and
exponent, strain-rate and thermal-softening parameters. Compared with classical elastoplastic theory
applicable to completely homogenous material, gradient-dependent plasticity considering the
microstructural effect predicts that phase transformation occurs earlier and that the thickness of
transformed ASB changes with flow shear stress.