Abstract
Aluminum silicon alloy of composition (Al-25%Si-3%Ni-1%Fe-2%Cu) was atomized using water atomization. The powders were cold compacted in a die to produce green cylinder compacts. Four consolidation processes were applied, namely; conventional sintering at 500℃, sintering followed by hot forging to obtain pistons, one step hot forging into pistons, and hot pressing. The microstructure of the sintered specimens showed inter-granular pores and oxide layers on particle interfaces of 84% relative density. When the sintered specimens were hot forged, both the inter-granular pores and oxide layers on particle interfaces almost disappeared and the relative densities increased up to about 95%. The same microstructure is also obtained for the one step forged specimens, but the relative densities increased to about 97%. However, the hot pressing specimens showed the presence of oxide layers on particle surfaces as well as few isolated pores. The relative density of the hot pressed specimens was about 90%. Hardness and ultimate compression strength were measured. It is noted that the strongest bulk materials are those made by hot forging, followed by those made by hot pressing and the weakest bulk materials are those made by conventional sintering.
Highlights
Aluminum alloys are light weight materials, and have excellent thermal conductivity, electrical conductivity, corrosion resistance, and workability
Four consolidation processes were applied, namely; conventional sintering at 500°C, sintering followed by hot forging to obtain pistons, one step hot forging into pistons, and hot pressing
It is noted that the strongest bulk materials are those made by hot forging, followed by those made by hot pressing and the weakest bulk materials are those made by conventional sintering
Summary
Aluminum alloys are light weight materials, and have excellent thermal conductivity, electrical conductivity, corrosion resistance, and workability. It is expected that alloys containing transition metals (Fe, Ni, Cr ) can precipitate fine intermetallic compounds from rapidly solidified powder leading to a high-strength as well as increased wear resistance at elevated temperatures. Most studies of powder forming used the yield functions for porous materials and ignored powder shape and size effects [14] In this investigation, Al-25%Si-3%Ni-1%Fe-2%Cu alloy has been atomized with water in order to refine the primary silicon phase by rapid solidification. Al-25%Si-3%Ni-1%Fe-2%Cu alloy has been atomized with water in order to refine the primary silicon phase by rapid solidification From these refined powders, automotive pistons of small size were fabricated using powder metallurgy route combined with hot forging and hot pressing processes
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