Abstract

The comprehensive properties of a feedstock have a critical influence on the powder injection molding process. Proper feedstock with homogeneous structure, favorable flow characteristic, and moldability is the prerequisite for obtaining a final part with excellent comprehensive properties. The objective of the present work was to develop an optimal feedstock for fabrication of hypereutectic AlSi (20 wt.%) alloy parts by the powder injection molding technique. For this purpose, micron-sized hypereutectic AlSi (20 wt.%) alloy powder was mixed with different amounts of a binder which consisted of 35 wt.% high-density polyethylene, 62 wt.% carnauba wax, and 3 wt.% stearic acid. The binder contents of the feedstocks were in the range from 13 wt.% to 21 wt.%. The influences of binder content, shear rate, and temperature on the rheological behaviors of feedstocks have been investigated via a capillary rheometer. The feedstock with 21 wt.% binder exhibited a variable flow behavior and was culled. The rest of the feedstocks showed a pseudoplastic behavior. Comprehensive analysis of rheological parameters such as the flow behavior index, yield stress, flow activation energy, and the general moldability index, the feedstock with 17 wt.% binder exhibited the best rheological performance and favorable moldability. The molded part with 17 wt.% binder had constant density, good shape retention, and stiffness as well as homogeneous distribution of the powder and binder. After solvent debinding, the debound item showed a homogeneous porous structure which is suitable for the subsequent thermal debinding and sintering processes.

Highlights

  • IntroductionEse alloys are generally produced by the casting process due to their excellent fluidity, low shrinkage, good hot tear resistance, and feeding characteristics

  • AlSi alloys have a relatively low thermal expansion coefficient and density, high wear resistance, and excellent thermal conductivity and have been extensively used in automotive, aerospace, and electronics industries [1, 2].ese alloys are generally produced by the casting process due to their excellent fluidity, low shrinkage, good hot tear resistance, and feeding characteristics

  • powder injection molding (PIM) is a developing net shaping technology by which metal/ceramic components with small sizes and complex geometries can be fabricated via batch production [10, 11]

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Summary

Introduction

Ese alloys are generally produced by the casting process due to their excellent fluidity, low shrinkage, good hot tear resistance, and feeding characteristics. Trends toward miniaturization of electronic components require aluminum alloy products possessing more complex geometries and smaller sizes. The powder injection molding (PIM) is a special and promising technology for manufacturing AlSi alloys with small sizes, delicate shapes, and complex geometries [8, 9]. PIM is a developing net shaping technology by which metal/ceramic components with small sizes and complex geometries can be fabricated via batch production [10, 11].

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