热-力场下纳米颗粒增强铝合金亚结构、析出相协同演变及强化机制

Aluminum alloys are the light-weight material of choice for automobile, defense and aerospace applications. However, the low strength and low creep resistance of aluminum alloys at elevated temperatures limit the applications. Most of previous investigations focus on the mechanical behavior at elevated temperatures controlled by only one strengthening mechanism such as substructure and dispersion hardening. Our preliminary research shows that the synergistic strengthening effect of prestrain-induced substructure, nano-particles and dynamic precipitates is more significant than dispersion strengthening only during high-temperature creep of precipitation hardened aluminum alloys, but the mechanisms are unclear. Thus, the present project focuses on the synergistic, competing evolution and strengthening mechanisms of prestrain-induced substructure, nano-particles and dynamic precipitates under thermo-mechanical fields, aiming at: revealing the interaction mechanisms for the effect of substructure and nano-particles on precipitation kinetics, the effect of nano-particles and precipitates on substructure evolution and thermal stability under thermo-mechanical fields; establishing a model of the synergistic evolution; revealing multi-component synergistic effect on high-temperature strength, ductility and creep behavior; achieving microstructure and multi-component synergistic strengthening controllable. Accomplishment of the above objectives will provide important experimental evidence and theoretical reference for thoroughly exploring synergistic evolution of microstructure, multi-component strengthening mechanisms and performance prediction under thermo-mechanical fields.

铝合金是汽车、国防、航空航天等领域轻量化的首选材料，但其高温强度低、易蠕变，限制其应用。以往研究主要关注亚结构强化、弥散强化等单一强化机制对高温力学行为的作用规律与机制，而申请人前期研究发现在析出强化铝合金高温蠕变过程中预应变引入的亚结构、纳米增强相、动态析出相三者协同强化效果大于单一强化的现象，但三者协同作用规律及强化机制尚不清楚。因此，本项目拟在预应变亚结构、纳米增强相、动态析出相三者协同、竞争演变机制和三者协同高温强化机制上取得新进展：揭示铝合金在热-力场下预应变亚结构与纳米增强相对析出相析出动力学、纳米增强相与析出相对亚结构演化和热稳定性的影响规律与作用机制，建立三者协同作用模型；揭示三者对高温强度、塑性和蠕变行为的协同作用规律与机制，实现组织与多元协同强化可控。上述目标的实现将为深入探索热-力场下组织协同演变机制、多元强化机理及预测服役行为提供重要的实验依据和理论参考。

铝合金是交通运输和国防等领域轻量化的首选材料，但其高温强度低、易蠕变，限制其在高温服役环境应用。以往研究主要关注亚结构强化、弥散强化等单一强化机制对高温力学行为的作用规律与机制，而本项目研究预应变引入的亚结构、纳米增强相、动态析出相三者在高温下的协同作用规律及强化机制。研究表明TiC纳米颗粒能促进铝合金凝固形核、细化晶粒、减轻微观偏析，进而促进析出反应，并且在室温高温都有弥散强化作用。大预应变0.2wt%TiC/Al-Mn-Mg在300ºC拉伸屈服强度与断后延伸率分别达到95MPa和35%，高于常规时效强化铝合金。但大预应变会促进再结晶和析出相粗化，降低组织热稳定性。本项目在预应变亚结构、纳米增强相、动态析出相三者协同、竞争演变机制和三者协同高温强化机制上取得如下进展：揭示预应变亚结构、纳米增强相对析出相析出动力学的影响规律与作用机制，阐明纳米增强相与析出相对亚结构演化和热稳定性的影响规律与作用机制，建立了亚结构与析出相协同演化模型；揭示亚结构、析出相、纳米颗粒增强相对高温强度、塑性和蠕变行为的作用规律与机制。本项目为设计新型弥散强化耐热变形铝合金及其服役行为预测提供重要的实验依据和理论参考。