Abstract
The evolution of three major heat-resistant phases (δ-Al3CuNi, γ-Al7Cu4Ni, T-Al9FeNi) and its strengthening effects at high temperature in Al–Si piston alloys with various Fe/Ni ratios were studied using field emission scanning electron microscope (FE-SEM), electron probe microanalysis (EPMA), and X-ray diffraction (XRD). With the increase of Fe/Ni ratios, the heat-resistant phases begin to evolve in category, morphology, and distribution. The results show that a suitable Fe/Ni ratio will cause the T-Al9FeNi phase to appear and form a closed or semi-closed network with δ-Al3CuNi and γ-Al7Cu4Ni phases instead of the originally isolated heat-resistant phases. As a result, the ultimate tensile strength of the optimized alloy reached 106 MPa with a Fe/Ni ratio of 0.23, which was 23.3% higher than that of base alloy at 350 °C, which is attributed to the fact that a closed or semi-closed network microstructure is advantageous to the bearing of mechanical loads. This work may provide useful ideas for the development of high temperature resistant piston alloys.
Highlights
Al–Si multicomponent piston alloys have been widely used in automobile manufacturing, such as in automobile engine pistons, owing to good castability, high elevated-temperature strength, light weight, good wear resistance, and low thermal expansion [1,2,3]
In order to meet the requirements of energy saving and emission reduction, the continuous improvement of engine efficiency has caused the working load of the piston to increase significantly, which puts higher requirements on the high temperature performance of the piston [4,5]
Li et al [8] and Yang et al [9] studied the changes in the category and morphology of heat-resistant phases with the addition of different Cu content, and the effect of heat-resistant phases at elevated-temperature on the properties of Al–Si alloys
Summary
Al–Si multicomponent piston alloys have been widely used in automobile manufacturing, such as in automobile engine pistons, owing to good castability, high elevated-temperature strength, light weight, good wear resistance, and low thermal expansion [1,2,3]. Researchers are paying more attention to the elevated-temperature properties of Al–Si piston alloys [6,7]. A lot of work has been done to improve the elevated-temperature performance of Al–Si piston alloys in the past decades. Feng et al [10] investigated the effects of thermal stable ε-Al3 Ni phase content on Al–Si microstructure, mechanical properties and low cycle fatigue at 350 ◦ C. Qian et al [7] added Mn from 0.04% to 0.4% into ZL109 piston alloy and found that the solubility of Mn in dendritic Al9 FeNi phase plays an important role in strengthening alloys
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