电解加钛共晶铝硅活塞合金的组织和性能研究

【作者】 王杰芳；

【导师】 谢敬佩；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2005， 博士

【摘要】 本文以汽车、摩托车发动机活塞使用的共晶铝硅合金材料为研究对象，直接使用电解低钛铝基合金细晶铝锭替代纯铝锭配制共晶铝硅ZL108试验合金（简称EZL108Ti），详细分析研究了该试验合金的微观组织、室温和高温力学性能、磨损性能，对电解加钛EZL108Ti合金的晶粒细化机理、强化机理及磨损机理进行了探讨。在此基础上进行了电解加钛EZL108Ti合金在摩托车活塞上的应用研究，并对试验活塞进行了台架试验。结果表明：直接采用电解低钛铝基合金完全可以制备出高性能的活塞，在汽车、摩托车发动机活塞行业具有广阔的应用前景。 首次对不同钛含量电解加钛共晶铝硅试验合金的微观组织进行了对比分析研究，发现当钛含量为0.10％左右时，电解低钛铝基合金表现出了最佳的晶粒细化效果。此时，电解加钛试验合金的α（Al）二次枝晶臂间距最小为16.71μm；共晶Si颗粒的长径、短径和直径最小，分别为3.28μm、2.29μm和2μ69μm；金属间化合物富Fe相的形态从鱼骨状转变成典型的汉字状，分布在晶界或枝晶间，外形圆钝，是高温热稳定相，对提高合金的高温性能非常有利。相同钛含量电解加钛和熔配加钛试验合金的α（Al）二次枝晶臂间距和共晶Si颗粒尺寸相差不大。 分析了钛对试验合金的细化机理：电解加钛共晶铝硅试验合金的微观组织细化与电解低钛铝基合金中均匀细小、高度弥散分布的Al₃Ti第二相质点有紧密的联系。在钛含量低于0.15％时，成份过冷引起的非自发形核以及钛元素抑制铝晶粒长大是钛细化合金的重要原因。同时，由于合金中Si、Mg、Cu等元素的存在可降低Al-Ti包晶反应温度和钛在铝液中的溶解度，使包晶点成分向低钛量方向位移，因此，即使钛含量低于0.15％，包晶反应可能也在起作用。共晶硅相总是与α（Al）相协调生长，随着α（Al）相的细化，也会相应细化合金中的硅颗粒尺寸，改善硅颗粒形状。当合金中的钛含量超过0.13％时，熔体中形成的第二相粒子将聚集、长大，晶粒细化作用逐步减弱。 首次对比分析研究了共晶铝硅不加钛ZL108、不同钛含量电解加钛EZL108Ti和熔配加钛MZL108Ti活塞合金的力学性能，结果表明：电解加钛试验合金的室温力学性能在钛含量范围0.10％～0.13％时较高，抗拉强度达到更多还原

【Abstract】 In this paper, the eutectic Al-Si alloys used in pistons of automobile and motorcycle engine have been studied mainly. The eutectic Al-Si ZL108 experimental alloys are produced directly by the electrolytic low-titanium Al-based alloy ingots replacing the pure aluminum ingots, which named EZL108Ti. The microstructure, mechanical properties at room and elevated temperature as well as the wear performance of the eutectic Al-Si EZL108Ti piston alloys adding titanium by electrolysis are investigated in detail. The mechanism of grain refinement, strengthening and wear resistance of the alloys is analyzed carefully. Based on above the investigation, the application of EZL108Ti alloys in pistons of motorcycle and the stand test of experimental pistons are made. The results show that it is feasible for the electrolytic low-titanium Al-based alloys to be used directly to produce high quality pistons, this kind of EZL108Ti pistons should have good prospect of application in pistons of automobile and motorcycle engine.The microstructure of the eutectic Al-Si alloys with different titanium content adding titanium by electrolysis are analyzed and investigated comparatively for the first time. The results show that the microstructure of experimental alloys adding titanium by electrolysis is refined remarkably, when titanium content in the alloys is about 0.10%. Here, the α (Al) second dendrite arm spacing is minimum which is 16.71 μm. The long diameter, short diameter and mean diameter of the eutectic silicon particles are all minimum which are 3.28 μm, 2.29 μm and 2.69 μm respectively. The morphobgy of tntermetallic compound iron-rich phases turn from fish-bone shape to typical blunt Chinese characters shape, distributing in grain boundary or interdendrite, it is heat-stability phase at elevated temperature and helpful to improve mechanical properties of experimental alloys at elevated temperature. Comparing the microstructure of experimental alloys adding titanium by electrolysis with that adding titanium by Al-Ti master alloys, their α (Al) second dendrite arm spacing and the size of eutectic silicon particles are almost equivalent.The refinement mechanism of titanium on experimental alloys is analyzed. The更多还原