Abstract
Three different compositions of high-Si Al alloy pipe, with a gradient structure, were produced through semi-solid rheological squeeze casting, the microstructural characteristics of which were investigated. The mechanism of gradient structure formation and the effect of acicular Fe-rich phases on liquid segregation were revealed. Meanwhile, the crystal structures of the Al4FeSi2 and Al15(Fe, Mn)3Si2 phase were elucidated. The relationship between the volume fraction of hard particles in the pipe wall and the macro-hardness was established. Wear resistance tests of the inner surfaces of the pipe walls, and tensile strength tests at different positions around the pipe walls, showed that the δ-Al4FeSi2 phase (acicular Fe-rich phases) reduced the wear resistance and the tensile strength of the alloy. In this study, the gradient distribution of the hard particles caused the outside of the pipe wall to have a higher tensile strength.
Highlights
Al-Si alloys have good casting properties, stable hightemperature performance, and its casting has good air-tightness[1,2]
The phase analysis and the structure of Fe-rich phases of the alloys were analysed by using a Focused Ion Beam (FIB) for sampling (Quanta 3D FEG scanning electron microscope (SEM)/FIB Dual Beam, FEI Co.) and Transmission Electron Microscopy (TEM) (Tecnai G2-F30-S-TWIN, FEI Co.), respectively
The analysis showed that the Al4FeSi2 phase was in the form of a tetragonal structure with lattice constants a = 0.60641 nm and c = 0.95258 nm, and the blocky Al15(Fe, Mn)3Si2 phase was a body centred cubic structure with lattice constants a=
Summary
Al-Si alloys have good casting properties, stable hightemperature performance, and its casting has good air-tightness[1,2]. For improving the wear resistance of the cylinder bore of the engine, additional coating with wear-resistant materials on the surface or casting iron cylinder liner inserts for the cylinder block are effective 10. Considering the cost of manufacture, the high-Si Al alloy cylinder liner, with a gradient structure in the radial direction was produced by the centrifugal casting process[11]. This kind of cylinder liner has a gradient structure containing a Si-rich area on the inner surface and a Si-poor area on the outer surface. The Si-rich area could provide the necessary wear resistance and the Si-poor area on the outer surface has a similar chemical composition to that of the cylinder block. The wear resistance of the inner surface of alloy pipes, and the tensile strength of the alloy pipes, were investigated
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