Study on Hypereutectic Al-Si Piston Alloy

Abstract: The dissertation investigates high silicon hypereutectic Al-Si piston ZS24 alloy. By contrasting several elements’modification effect, the investigation obtains an efficient crystal modifier which can markedly modify both primary silicon and eutectic silicon. Based on the silicon’s modification, the study contrives a new type piston alloy with slight crystalline particle and outstanding mechanical, physical properties. According to a series of experiments and analysis, such achievements are educed:Depending on the single and dual modification of P, RE, Sr elements on primary and eutectic silicon, the investigator find an efficient P-RE-Sr triplex modifier. Modified by the triplex modifier, the coarse primary silicon of ZS24 alloy turns to be obtuse, and its average diameter decreases sharply from 100~150μm to 10~15μm. Meanwhile, the eutectic silicon turns from acicular crystals to be vermiform, excelling what is modified with PM modifier.The paper researches the connection among ingredients, structure and property of the ZS24 alloy through normal experiment measure, maximal dispersion and curvilinear regression analysis. The results reveal that influents of Cu, Mg, Mn elements onσb,σb,300℃, and HBS have markedly difference. According to the analysis, ingredients of ZS24 alloy are established.The investigation measures the alloy’s mechanical and physical properties. The results indicate that intensity of tension at room temperature is from 217.84 to 242.91MPa, and intensity of tension at 300℃from 127.39 to 143.57MPa. Compared with ZL109 alloy, which is from 196 to 290MPa, the ZS24 alloy’s intensity of tension is a little lower at room temperature. However, its intensity of tension at high temperature is much more than ZL109 alloy, that from 70 to 90MPa. As a result, the ZS24 alloy suits for piston which often works in the state of high temperature and heave stress. Experiments show that linear dilatability of ZS24 alloy is 17.5~19.5℃-1, fewer than 20.9℃-1 of ZL109 alloy. Moreover, ZS24 alloy’s wear-resistant is superior to that of ZL109 alloy. Attrition of the alloy is only 1.060~1.066m3·N-1·m-1, corresponding 2.708m3·N-1·m-1 of ZL109 alloy.The dissertation mainly studies ZS24 alloy on both influences of modification on primary and crystal silicon’s crystalline dimension, shape and form, and effect of Cu, Mg and Mn elements on mechanical, physical properties. And the investigation finally obtains a new hypereutectic Al-Si piston alloy. As a groping research, the harvest may offer a helpful approach for piston alloys’research and have considerable academic and practical significance…
Key words: ZS24 Hypereutectic Al-Si Alloy; Multiplex Modification; Optimization Design; Mechanical Property; Physical Property

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