高强双相铝合金相图、相结构及热稳定性研究

High-strength aluminum alloy is an important subject in the research of aluminum alloy. Amorphization is an important way to improve the strength of the traditional aluminum alloys. However, the maximum shear imposed on amorphous alloys has to be kept to 2%, owing to the shear-band softing effect, which is caused by the localization of shear strain in the metlallic glasses during plastic deformation. And the amorphous / nanocrystalline structure can be used as a route to improve the strength of alloys. However, the coarsening of nanocrystalline will significantly weaken the mechanical properties of the dual-phase aluminum alloys. Therefore, it is the key problem to obtain the nanostructure phase with good thermal stability at a wide temperature range. The CALPHAD method can efficiently predict the thermal stability of nanocrystalline. The purpose of this project is to systematically study the Al-TM (Co, Ni, Fe) -RE (Er, Yb, Sc) phase diagrams, and establish the corresponding thermodynamic database. The glass forming ability of alloys and the precipitation range and composition of L12 nanocrystal-structure can be predicted, and the thermal stability of nanoscale phase can be simulated, which provides important data for designing of high-strength aluminum alloys with dual-phase nanostructure.

高强度铝合金是目前铝合金研究的重要课题。非晶化是提高传统铝合金强度的重要手段，但是非晶铝合金形变过程中的剪切应力集中所导致的剪切带的软化效应使其能承受的最大应力只能被限制在2%的应变处，需要采用非晶/纳米晶双相结构共同作用来进一步提高铝合金的强度。不过纳米晶粒的粗化会显著削弱双相铝合金的力学性能。因此，能否在较宽的温度范围获得热稳定性好的纳米结构相是高强度铝合金研究的关键问题。相图计算（CALPHAD）方法可以快速高效的预测纳米晶的热稳定性。本项目拟综合运用平衡合金法和相图热力学计算方法,系统研究Al-TM（Co, Ni, Fe）-RE（Er, Yb, Sc） 多元相图，建立相应的相图热力学数据库。并在此基础上，预测各个合金体系的非晶形成能力及L12结构纳米晶的析出范围及成分，探讨纳米尺度相的热定稳性，为设计高强度双相铝合金提供重要的基础数据。

采用平衡合金法，结合电子探针显微分析技术（EPMA）、X射线衍射技术（XRD）及热分析（DSC）等检测分析手段，实验测定了Al-Ni-Er、Al-Ni-Nd、Al-Ni-Pr、Al-Ni-Sc、Al-Co-Er、Al-Ag-Sc、Al-Ag-Zr、Al-Ag-Si、Al-Ca-Y、Al-Ti-Nb等铝合金体系的相图。依据新的实验相图结果，在已有热力学数据的基础上辅助以第一性原理计算，运用CALPHAD方法对Al-Ni-Er、Al-Ni-Nd、Al-Ni-Pr、Al-Ni-Sc、Al-Ag-Sc、Al-Ag-Zr、Al-Ag-Si、Al-Ca-Y、Al-Ti-Nb等体系进行了热力学优化计算，得到了较为合理的热力学参数，并构建了Al-TM-RE多元体系相图热力学数据库。在此基础上设计不同微合金化下的Al-Cu-Mg-Ag合金，实验比较不同微合金化元素成分及热处理工艺对耐热铝合金析出相的影响，并从相图热力学角度探讨了复合微合金化对耐热铝合金析出过程的机理。