选区激光熔融Ti基金字塔型点阵材料对Mg/Ti液固复合铸造界面的强化机理

Magnesium and titanium is the most important light weight metals which has highly complementation of properties, and there is a great application prospect in Mg/Ti liquid-solid compound casting. The problem of Mg/Ti liquid-solid compound casting is the low strength caused by the weak reaction and low mutual solubility. In this research, a new strengthen method of interface based on the Ti based pyramid lattice materials produced by selective laser melting (SLM) has been put forward. This research focuses on the scientific problem of strengthening mechanism worked in Mg/Ti liquid-solid compound casting interface. Physical and chemical properties of the SLM lattice materials on titanium surface have been characterized and their surface wettability was regulated. Main factor and best parameter which impact the interface strength were determined by orthogonal experiment. Situ test inversion analysis of micronano indentation and support vector machine (SVM) of Matlab have been used to establish a prediction model of interfacial constitutive equation which was adaptive to all factors under research condition and have self-learning function. Combined with a finite element analysis, shear strength experiment, fracture analysis, the effects of structure parameters of lattice material on shear strength has been investigated, and the strengthening mechanism of lattice material worked in the interface of Mg/Ti liquid-solid compound casting has been revealed. The achievements of the project will provide theoretical support for the new method of interface reinforcement of Mg/Ti liquid-solid compound casting and reference for the interface reinforcement of liquid-solid compound casting between other melting which has weak reaction and low mutual solubility.

Mg、Ti同为重要的轻量化金属，性能互补性很强，Mg /Ti液固复合铸造具备很好的应用前景。针对Mg、Ti由于弱反应低互溶产生的液固复合铸造界面强度低的难题，本课题提出一种基于选区激光熔融Ti基金字塔型点阵材料的界面强化新方法，围绕其强化机理的科学问题，表征钛材表面SLM点阵材料的理化特性并调控其表面润湿性，通过正交实验确定影响界面强度的主次因素及最优因素水平组合，采用微纳米压痕原位测试反演分析及Matlab支持向量机建立可在与研究条件相同的其他案例中使用的、具有自学习功能的结合面力学本构方程预测模型，结合有限元分析、剪切强度实验、断口分析研究点阵材料结构参数对剪切强度的影响规律，揭示点阵材料在Mg/Ti液固复合铸造界面的强化机理。项目的完成将为Mg/Ti液固复合铸造界面的强化新方法提供理论基础，为其界面设计提供支撑，为其它弱反应低互溶金属之间的液固复合界面强化提供借鉴。

针对Mg、Ti由于弱反应低互溶产生的液固复合铸造界面强度低的难题，本项目将SLM增材制造及点阵材料应用于Mg/Ti液固复合铸造界面强化，充分利用Ti基金字塔型点阵材料的高比表面积及与镁合金形成的三维互嵌结构，强化冶金结合与机械结合。围绕其强化机理的科学问题，研究了电镀Ni、电镀Cu、热浸镀Al/Zn等作为中间金属层对于Ti6Al4V和AZ91D镁合金液固复合铸造的影响，分析和对比了不同工艺条件下的界面处扩散反应区组织,研究了Ti6Al4V/AZ91D双金属组织演变、性能和断裂行为，采用微纳米压痕实验结果反演分析及支持向量机建立了 Ti 基金字塔型点阵材料结合界面本构模型，研究了金字塔型点阵材料的结构参数对界面结合强度的影响并优选了其的最佳结构参数范围。研究结果表明：结合强度高的点阵结构的最佳参数范围为：杆单元倾斜角(ω)和杆间夹角为45°，0.6 mm<杆径(d)<2 mm，1.2＜长径比(l/d)<5，2.5<上下节点比(d1/d, d2/d)<3.2。在Ti表面采用金字塔型点阵结构并电沉积Ni时，在浇注温度不低于 690-750℃的条件下，Mg/Ti界面可以得到由（Mg2Ni +α-Mg）、Ni2Mg3Al、Al3Ni 组织组成的界面扩散反应区，结合强度达到135.4 MPa。结合有限元分析、剪切强度实验、断口分析研究点阵材料结构参数对剪切强度的影响规律，揭示了点阵材料在Mg/Ti液固复合铸造界面的强化机理。同时，本项目将奠定点阵材料和液固复合铸造制备Mg/Ti双金属复合材料的技术基础。