High strength Al 7075 alloy was manufactured via twin-roll strip casting (TRC) process, and its microstructure, tensile and fatigue properties were investigated. Commercial Al 7075 alloy fabricated via direct-chill (DC) casting process was also used for comparison. T6 and T651 heat treatments were implemented for both the materials to precipitate MgZn₂(η) phases. The TRC alloy showed globular grain shape with η phases evenly distributed at the grain boundary and matrix interior, while the DC alloy showed elongated grains due to hot forging process and η phases clumped together at grain boundaries. The TRC alloy’s yield strength was 518.5 MPa, tensile strength was 578.2 MPa, and elongation was 6.9%. Comparing both the alloys’ mechanical properties, the TRC alloy’s strength was at least about 40 MPa higher and elongation was about 4% lower than the DC alloy. The TRC alloy showed about 20 MPa higher fatigue (fatigue limit) than the DC alloy. The DC alloy was observed to have coarse cracks on fatigue fractured surface. By contrast, the TRC alloy showed uniform fractured surface without coarse cracks, and the evenly-distributed η phases improved fatigue resistance efficiently. The present study sought to examine the correlation among TRC process-led microstructure, tensile and high-cycle fatigue properties while discussing the strengthening mechanism.

通过双辊薄带连铸（TRC）工艺制造了高强度Al 7075合金，并对其微观结构，拉伸性能和疲劳性能进行了研究。通过直接冷却（DC）铸造工艺制造的商业Al 7075合金也用于比较。两种材料均进行了T6和T651热处理，以沉淀MgZn ₂（η）相。TRC合金显示出球状晶粒形状，η相均匀分布在晶界和基体内部，而DC合金由于热锻造工艺显示出细长的晶粒，η相在晶界聚集在一起。TRC合金的屈服强度为518.5 MPa，抗拉强度为578.2 MPa，伸长率为6.9％。比较两种合金的机械性能，TRC合金的强度至少比DC合金高约40 MPa，而伸长率比DC合金低约4％。TRC合金的疲劳度（疲劳极限）比DC合金高约20 MPa。观察到该DC合金在疲劳断裂表面上具有粗大裂纹。相反，TRC合金显示出均匀的断裂表面而没有粗大的裂纹，并且均匀分布的η相有效地提高了抗疲劳性。