【作者】 章杰；

【导师】 孔毅； 陈利；

【作者基本信息】 中南大学 ， 材料学， 2025， 博士

【摘要】 TiAlN涂层在切削热的作用下发生调幅分解而产生的自硬化效应,是其成功应用于切削刀具的关键因素之一。然而,随着切削温度的进一步上升,TiAlN涂层的调幅分解产物会向其稳定相六方（w）Al N转变而导致其力学性能下降,从而影响涂层刀具的高温服役性能。近来,基于多层结构和多元掺杂调控TiAlN涂层的热分解行为,尤其是抑制w-Al N的相转变,受到了研究者的广泛关注。但是,上述两种改性策略对TiAlN涂层结构和热分解行为的作用机理尚不明确,掺杂元素的选择以及多层界面的设计也亟需解决。为此,本论文首先采用第一性原理计算结合机器学习系统地研究了不同过渡族金属对TiAlN涂层相结构稳定和热分解行为的影响规律;然后,通过氧添加改性TiAlN涂层,并结合理论计算揭示其相结构和热稳定性的强化机制;最后在TiAlN中分别引入TiN、ZrN和CrN共格界面层,通过不同共格界面调控TiAlN涂层的热分解行为。取得的主要成果如下:（1）提出一种第一性原理结合机器学习预测Ti_1-x-yAl_xTM_yN无序固溶体全成分范围内相结构和热稳定性的研究方法。结合Magpie特征描述符和线性回归模型搭建了Ti_1-x-yAl_xTM_yN（TM=Sc、Y、Zr、Hf、V、Nb、Ta、Cr、Mo和W）的形成焓和体积数据库,研究表明d轨道价电子浓度较高的Nb、Ta、Mo和W添加增加Al在立方TiN中的固溶度,提高了涂层的相结构稳定性。基于形成焓数据库建立了Ti Al TMN体系的典型混合焓和渐进混合焓计算方法,表明适量的Nb、Ta、Cr、Mo和W添加降低了调幅分解驱动力从而抑制了其热分解行为。另外,Ti_1-x-yAl_xTM_yN体系的调幅分解沿渐进混合焓增加最快的路径实现双相分离,同时持续扩大的晶格差异导致了时效硬化现象。（2）氧添加提升TiAlN涂层的相结构稳定性,并抑制了涂层的热分解行为。(Ti_1-xAl_x)(O_yN_1-y)_z涂层在氧含量低于0.18时呈单相面心立方结构,硬度维持在～32 GPa。TiAlN和Ti Al ON涂层的热分解行为由Al的扩散所主导,氧添加通过增加Al的上坡扩散激活能,从而延缓了调幅分解以及随后六方相变过程,显著提升了TiAlN涂层的热稳定性能。（3）TiAlN/TiN纳米多层涂层共格界面诱导的调幅分解促进了TiAlN层的热分解。TiAlN单层涂层在800°C退火后发生调幅分解,在1100°C退火后于晶界处形成w-Al N。TiAlN/TiN纳米多层的共格界面的诱导作用促进了TiAlN层的调幅分解在层间界面处优先发生;且Al原子在层间界面驱动下垂直于界面向层内扩散,致使TiAlN层演变成自组织的（Al,Ti）N/（Ti,Al）N/（Al,Ti）N/（Ti,Al）N/（Al,Ti）N多层结构;并最终导致w-Al N在平行于界面方向以层状结构在更低的温度1000°C时生成,层状w-Al N的生成延缓了涂层硬度的下降趋势。（4）TiAlN/ZrN多层涂层在沉积过程中形成的非对称界面提高了涂层的热稳定性。在ZrN层表面沉积TiAlN层时,Ti的吸附能下降致使ZrN层表面优先沉积（Ti,Zr）N层,然后再沉积TiAlN层,最终形成了ZrN/（Ti,Zr）N/TiAlN的多层结构。（Ti,Zr）N层提高了界面处Al的扩散激活能,致使界面诱导的调幅分解优先在TiAlN层和ZrN层的界面处发生;且Al原子沿垂直于界面向ZrN层方向扩散,延长了TiAlN层中Al原子的扩散路径,并最终导致w-Al N以层状结构在更高的温度1200°C时生成,提高了涂层的热稳定性。（5）CrN层的顺磁性促进了TiAlN/CrN多层涂层的热分解行为。CrN层退火后呈现顺磁态排列特性,通过降低Al的扩散激活能促进了TiAlN/CrN多层涂层的界面诱导调幅分解,致使TiAlN层在900°C退火后演变成自组织的（Al,Ti）N/（Ti,Al）N/（Al,Ti）N多层结构;随温度升至1000°C,Cr越过（Al,Ti）N层向中间（Ti,Al）N层扩散,导致多层结构坍塌。图116幅,表5个,参考文献385篇更多还原

【Abstract】 The self-hardening effect generated by the spinodal decomposition of TiAlN coatings under cutting thermal loads is one of the key factors for their successful application in cutting tools.However,as cutting temperature continue to rise,the spinodal decomposition products of TiAlN coatings undergo phase transition to their stable wurtzite（w-）Al N,which results in deteriorated mechanical properties and affects the high-temperature service performance of coated cutting tools.Recently,the regulation on the thermal decomposition behavior of TiAlN coatings through multilayer structure and multiple doping,especially the inhibition of w-Al N phase transformation,has received extensive attention.Nevertheless,the mechanisms by which the two modification strategies affect the structure and thermal decomposition behavior of TiAlN coatings remain unclear,and challenges persist in selecting doping elements and designing multilayer interfaces.To address these issues,the effects of different transition group metals on the structure and thermal decomposition behavior of TiAlN were investigated systematically using high-throughput first-principles calculations combined with machine learning.Subsequently,TiAlN coatings were modified by non-metallic oxygen addition,which was combined with theoretical calculations to reveal the phase structure and strengthening mechanisms of thermal stability.Finally,TiN,ZrN and CrN coherent interfaces were individually introduced into TiAlN to regulate the thermal decomposition behavior of TiAlN coatings.The main findings were summarized as follows:（1）A research approach was proposed to predict the structural and thermal stability variations of Ti_1-x-yAl_xTM_yN disordered solid solutions across full compositional ranges by high-throughput first principles and machine learning.By constructing formation enthalpy and volume databases for Ti_1-x-yAl_xTM_yN（TM=Sc,Y,Zr,Hf,V,Nb,Ta,Cr,Mo,W）with Magpie feature descriptors and linear regression models,it was revealed that Nb,Ta,Mo,and W addition with relatively high d-orbital valence electron concentrations increase the Al solubility in cubic TiN and enhance the phase structure stability.Based on the database of formation enthalpy,the typical and progressive mixing enthalpy of Ti Al TMN system were developed.It was demonstrated that moderate amount of Nb,Ta,Cr,Mo and W suppressed the thermal decomposition by decreasing the driving force for spinodal decomposition.Furthermore,spinodal decomposition of Ti_1-x-yAl_xTM_yN proceeded with dual-phase separation along the path of fastest-increasing progressive mixing enthalpy,the continuously enlarged lattice mismatch induces age hardening.（2）O addition enhanced the phase structure stability of TiAlN coatings and suppressed the thermal decomposition behavior of the coatings.(Ti_1-xAl_x)(O_yN_1-y)_z coatings with oxygen content below 0.18showed a single-phase face-centered cubic structure and the hardness maintained at～32 GPa.The thermal decomposition behavior of TiAlN and Ti Al ON coatings was dominated by Al diffusion,and oxygen-addition delays the spinodal decomposition of TiAlN and subsequent wurtzite transformation process by increasing the activation energy for the uphill diffusion of Al.（3）The thermal decomposition of TiAlN layers in TiAlN/TiN nano-multilayer coating was facilitated by coherent interface-induced spinodal decomposition.TiAlN coating underwent spinodal decomposition after annealing at 800°C,and w-Al N was formed at grain boundaries after annealing at 1100°C.The inductive effect by coherent interfaces in TiAlN/TiN nano-multilayer promoted the preferential occurrence of spinodal decomposition of TiAlN layers at interlayer interface.Moreover,Al atoms diffused into the layer perpendicularly to the interface under the drive of the interlayer interface,resulting in TiAlN layer evolving into a self-organized（Al,Ti）N/（Ti,Al）N/（Al,Ti）N/（Ti,Al）N/（Al,Ti）N/（Al,Ti）N multilayer structure.This ultimately leads to the generation of layered structured w-Al N parallel to the interfacial direction at a relatively low temperature of 1000°C,which retards the decreasing trend of hardness.（4）The asymmetric interfaces formed during the deposition improved the thermal stability of TiAlN/ZrN multilayers.When the TiAlN layer was deposited on the ZrN surface,the decrease in the adsorption energy of Ti leads to the preferential deposition of（Ti,Zr）N layer on the surface of ZrN layer,followed by the deposition of TiAlN layer,and finally a multilayer structure of ZrN/（Ti,Zr）N/TiAlN was formed.The（Ti,Zr）N layer increases the activation energy of Al diffusion at the interface,leading to interface-induced spinodal decomposition preferentially occurring at the interface between the TiAlN and ZrN layers.Besides,The diffusion of Al to ZrN layer,along the direction perpendicular to the interface,prolonged the diffusion path of Al atoms in the TiAlN layer.Eventually,w-Al N was generated in a layered structure at a relatively high temperature of 1200°C,which improves the thermal stability of coating.（5）Paramagnetism of CrN layer promotes thermal decomposition behavior of TiAlN/CrN multilayers.The CrN layer with paramagnetic arrangement after annealing promotes the interface-induced spinodal decomposition of TiAlN/CrN by reducing the activation energy of Al diffusion,which results in the evolution of the TiAlN layer into a self-organized（Al,Ti）N/（Ti,Al）N/（Al,Ti）N multilayer structure after annealing at 900°C.As the temperature rises to 1000°C,Cr crosses（Al,Ti）N layer and diffuses to the middle（Ti,Al）N layer,leading to the collapse of the multilayer structure.更多还原