铝熔体中TiCx@TCB核壳的结构调控及其对α-Al免疫形核机制的研究

Zr/Si致细化“中毒”成为制约超高强及高强铝合金发展的瓶颈，也是国内外铝加工业亟待解决的难题。项目提出在铝熔体中原位构筑TiCx@TCB核壳（TCB特指一种由Ti、C、B等元素组成的高温稳定相），以TCB核壳直接作为α-Al的形核衬底，克服复相形核存在细化“毒化”的弊端。利用液态金属X射线衍射仪等手段，以Al-Ti-C-X系熔体结构研究为基础，从TiCx空位调控入手，借助B诱导其结构演变，原位构筑TiCx@TCB核壳，实现对TCB结构的精准调控。利用小角度X射线衍射等手段对TCB结构进行精细化表征，研究TCB/α-Al界面微结构、原子选择吸附、成键信息，以及TCB对铝晶粒细化的抗“中毒”行为，结合第一性原理建立TCB对α-Al的免疫形核机制。研制出抗“中毒”TCB晶种合金，破解超高强及高强铝合金细化“中毒”国际性难题，突破铝合金及其加工技术发展瓶颈。

The poisoning effect of Si and Zr on α-Al grain refining has restricted the development of ultra-high strength and high strength Al alloys and the process technologies, which is also a worldwide challenge in Al industry. This project has put forward a new thought using the in-situ synthesized TiCx@TCB core-shell structure acting as the nucleating sites for α-Al grains. The symbol TCB represents a phase structure containing elements Ti, C and B, which structural stble at high temperature. The TCB structure has high stability and exhibits anti-poisoning performance, thus can directly act as the nucleating sites for α-Al grains. Therefore, it can overcome the shortage of present multiphase nucleating theory by Ti-rich layer which is quite easy to be poisoned. The liquid X-ray Diffraction will be utilized to characterize the structure evolution behavior of Al-Ti-C-X melt. Based on the control of C vacancies in TiCx and by means of its structural evolution and transformation induced by B/N atoms, the TiCx@TCB core-shell structure will be in-situ built and precisely adjusted. The small angle X-ray diffraction and other techniques will be used to precisely characterize the TCB core-shell structure. By the experimental investigation of microstructure, atom selective adsorbing behavior, combination characteristic and bonding information in TCB/α-Al interface, and taking advantages of the investigation of nucleating mechanism for α-Al on TCB in Zr-containing Al alloys and Al-Si alloys together with the first-principle calculation, the anti-poisoning nucleating mechanism of TCB for α-Al will be built. Based on above investigation, novel crystal seed TCB master alloys with anti-poisoning performance will be developed, which can solve the international problems of refining-poisoning for hultra-high strength and high strength Al Alloys, and the bottleneck of Al alloys and their processing technologies will be also broken through.