Wang Jue, Li Faguo
School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China.
Materials (Basel). 2023 Jul 5;16(13):4846. doi: 10.3390/ma16134846.
The 7055 aluminum alloy is an ultra-high strength aluminum alloy, which is widely used in the aerospace field and new energy automobile manufacturing industry. As it retains high strength, its plastic deformation ability needs to be improved, which limits its application in plastic processing. In this study, the cast grains of the 7055 aluminum alloy were refined by adding Sm + Er, and the proper heat treatment procedure was utilized to further precipitate the rare earth phase in order to increase the alloy's strength and toughness. The grain size, microstructure and phase were characterized by optical microscopes (OMs), scanning electron microscopy-energy spectrum (SEM-EDS) and a XRD diffractometer (XRD). The macroscopic hardness, yield strength and tensile strength of alloy materials were measured by a hardness meter and universal electronic tensile machine. The results showed that the as-cast sample and the heat treatment sample all contained AlCuSm and AlCuEr rare earth phases. But, after heat treatment, the volume percentage of the rare earth phase dramatically increased and the dispersion was more unified. When 0.3 wt.%Sm and 0.1 wt.%Er were added, the grain size could be refined to 53 μm. With the increase in the total content of rare earth elements, the refining effect first increased and then decreased. Under 410 °C solid solution for 2 h + 150 °C and aging for 12 h, the macroscopic hardness, yield strength, tensile strength and elongation of 0.3 wt.%Sm + 0.1 wt.%Er + 7055 as-cast samples were 155.8 HV, 620.5 MPa, 658.1 MPa and 11.90%, respectively. After the addition of Sm and Er elements and heat treatment, the grain refinement effect of 7055 aluminum alloy was obvious and the plastic property was greatly improved under the premise of maintaining its high-strength advantage.
7055铝合金是一种超高强度铝合金，广泛应用于航空航天领域和新能源汽车制造业。由于其保持高强度，但其塑性变形能力有待提高，这限制了其在塑性加工中的应用。在本研究中，通过添加Sm+Er细化7055铝合金的铸态晶粒，并采用适当的热处理工艺进一步析出稀土相，以提高合金的强度和韧性。通过光学显微镜（OM）、扫描电子显微镜-能谱仪（SEM-EDS）和X射线衍射仪（XRD）对晶粒尺寸、微观组织和相进行表征。用硬度计和万能电子拉伸机测量合金材料的宏观硬度、屈服强度和抗拉强度。结果表明，铸态试样和热处理试样均含有AlCuSm和AlCuEr稀土相。但是，热处理后，稀土相的体积百分比显著增加，且弥散更加均匀。当添加0.3 wt.%Sm和0.1 wt.%Er时，晶粒尺寸可细化至53μm。随着稀土元素总含量的增加，细化效果先增大后减小。在410℃固溶2 h+150℃时效12 h条件下，0.3 wt.%Sm+0.1 wt.%Er+7055铸态试样的宏观硬度、屈服强度、抗拉强度和伸长率分别为155.8 HV、620.5 MPa、658.1 MPa和11.90%。添加Sm和Er元素并进行热处理后，7055铝合金的晶粒细化效果明显，在保持其高强度优势的前提下，塑性性能得到了极大改善。
