Hao He

The Granular Model in Powder Injection Molding

The granular model which is fit for discontinuous bodies is applied to powder injection molding. The powder is regarded as discrete particles which are immersed into binder. The powder three-dimensional flowing in powder injection molding has been simulated based PFC. The results show that the filling rate of granulars is anisotropy and injection molding is always filled in the central region of cavity where resistance is smaller. But the angular area where resistance is large often filled be the end, even if it is close to the center of pressure.

Fabrication and Bending Strength of Al/SiC Composites with High Volume Fraction of Reinforcement by Combining Powder Injection Molding and Pressure Infiltration

The paper presents the result of an experimental investigation on the fabrication of Al/SiC composites with high volume fraction of SiC particles by pressure infiltration of liquid aluminum into preforms prepared by powder injection molding (PIM). To obtain the required high particle volume fraction, SiC powders with a bimodal particle size distribution were used. The influence of powder loading and particle size on the bending strength of the prepared composites has been investigated. It is demonstrated that pressure infiltration permits to achieve high relative densities for the composites (i.e. 98.8%). The microstructure studies revealed a uniform distribution of SiC particles in the composites without interface reactions between the particles and the aluminum matrix. The bending strength increases with increasing powder loading and decreasing particle size of the coarse powders in the bimodal powder system.

The Research on Discrete Element of Blade Part In Powder Injection Molding

The 3D injection discrete element model of blade injection part is constructed. PFC3D is used to program for filling simulation and analysis. The simulation result shows that there is anisotropy and filling in injection direction first. There is difference between results by discrete element and by Moldflow software. There is large contact stress in reverse direction in sharp angle region and it is filled at last. The injection test result shows that the injection discrete element model is feasible.

Thermo-Physical Properties of SiCAl Composites with High Volume Fraction of Reinforcement Prepared by Combining Powder Injection Molding and Pressure Infiltration

SiC/Al composites with high reinforcement content were fabricated by pressure infiltration of aluminum alloy into porous SiC preform obtained by powder injection molding using a bimodal powder mixture. The influence of powder loading and particle size on the thermo-physical properties of the prepared composites was investigated. The results indicate that the thermal conductivities (TC) increases and coefficients of thermal expansion (CTE) decreases with increasing powder loading and particle size of the coarse powders in the bimodal powder system. The TCs are below the estimated value based on Hasselman-Johnson model, mainly due to the residual pores and the irregular particle shape. The CTEs of the composites increase with increasing temperature from 100°C to 400°C, and the increasing rates vary at different temperature ranges. Deep cooling in liquid nitrogen is effective to bring dislocations in the matrix and thus reduces the CTEs.

Effect of Molding Parameters on the Interface Morphology of Metal Co-Injection Molding

In the present study, the effect of injection temperature, velocity and delay time on the interface morphology of the co-injection molded plates was studied. The results showed that the core penetration parallel to the flow direction becomes less as the skin injection velocity and temperature increases and delay time decreases. Among the parameters, temperature was the most significant in affecting the interface morphology, followed by delay time, while injection velocity seemed to play no significant role. The results were analyzed by taking account of rheological properties of the two feedstocks. Calculations and comparisons of viscosity ratios encountered in experiments were made. It was demonstrated the differences in the rheological properties of the metal feedstocks involved are key factors in determining the interface morphology of the molded parts.

Effect of Sintering Temperature and Atmosphere on Corrosion Behavior of MIM 316L Stainless Steel

In the present study, effect of sintering temperature and atmosphere on corrosion behavior of 316L stainless steel specimens manufactured by metal injection molding (MIM) process were investigated. Sintering experiments were carried out at 1320°C, 1370°C and 1375°C under various sintering atmospheres, i.e. Ar+H2, Ar, N2+H2 or N2. The corrosion behavior of as-sintered specimens was studied by weight loss immersion test in 5%HCl solution. The results indicated that a better corrosion resistance was accompanied higher density, finer and rounder surface pores. The specimens sintered under Ar+H2 atmosphere at 1370°C had little susceptibility to intergranular corrosion.

An Experimental Study of Metal Co-Injection Molding with Sequential Injection

An experimental study of co-injection molding which involves sequential injection of dissimilar metal feedstocks into a mold has been carried out. The effect of skin temperature and injection velocity on the material distribution of co-injection molded plates has been studied. It was found that the molding temperature was important in controlling skin-core distribution, while injection velocity seemed to play no significant role. The experimental results were analyzed by taking account of the relative viscosity of the two melts. It was demonstrated that the differences in rheological properties of the metal feedstocks involved are the primary variable determining the phase distribution of the molded parts.