Basic investigations of the preparation and properties of in-situ Al3Ti reinforced aluminium cast alloys

限制铝铸件使用的因素往往不是它们的强度，而是合金的硬度。因此，该项目的目的是通过原位形成非常坚硬的金属间化合物相Al3Ti来显著提高铝铸造合金的硬度。由于钛在铝熔体中的溶解度很低，这是传统熔体冶金不可能做到的。为了制备微米级的Al_3Ti颗粒，采用了一种新型的高剪切装置，利用钛粉颗粒(约50μm)与铝液原位反应生成Al_3Ti。随着钛转变为Al3Ti的体积显著增加，以及由此产生的高应力，预计将导致Al3Ti相非常精细地破碎成微米级的颗粒。由于剪切单元施加的高剪切力，这些颗粒将从初始钛相分离并有效地分布在熔体中。从根本上分析了铸造铝合金中原位强化相的形成动力学及其强化效果。研究了硅、镁等典型压铸合金元素对压铸性能的影响。基于这一认识，最终目的是设计出一种自生增强铝合金，其硬度大大超过商业压铸合金。

Limiting for the use of aluminum castings is often not their strength, but the stiffness of the alloy. The aim of this project is therefore to increase significantly the stiffness of aluminum casting alloys by in situ formation of the very stiff intermetallic phase Al3Ti. Due to the low solubility of titanium in the aluminum melt, this is not possible by conventional melt metallurgy. In order to generate micrometer sized Al3Ti particles, an in-situ reaction of Ti powder particles (about 50 μm) with liquid aluminum to Al3Ti combined with a novel high-shear unit is used. The significant increase in volume associated with the conversion of titanium to Al3Ti and the resulting high stresses are expected to lead to a very fine fragmentation of the Al3Ti phase into micrometer-sized particles. These particles will be detached from the initial titanium phase and effectively distributed within the melt due to the high shear forces applied by the shear unit. The formation kinetics of the in-situ reinforcement phase and its reinforcement effect in aluminum cast alloys is fundamentally analyzed. The influence of typical die casting alloying elements such as Si and Mg is investigated. Based on this knowledge, the ultimate aim is to design an in-situ reinforced aluminum alloy whose stiffness exceeds significantly that of commercial die casting alloys.