Enhancing the strength and sensitization resistance of Al–Mg–Mn alloy via the modification of β-Al3Mg2 precipitates induced by Nd and Sr addition

Abstract

In this work, the Nd and Sr elements were introduced into a special AA5083 (Al–Mg–Mn, 5XCT3, wCr + wTi = 0.3 wt%) alloy for modifying the β-Al3Mg2 precipitates, to investigate the influence of Sr and Nd on the mechanical properties and sensitization resistance. The results show that there is a significant enhancement on the yield strength (∼196 MPa) and tensile strength (∼343 MPa) because of the precipitation strengthening. After a sensitization treatment at 175 °C for seven days, the mass loss of the Nd- and Sr-modified 5XCT3 alloys in the nitric acid mass loss test (NAMLT) is 23.6 mg/cm2, which is still below the intergranular corrosion (IGC) susceptibility limit (25 mg/cm2). Meanwhile, the IGC resistance of the Nd and Sr modified alloys is significantly improved, as compared with the unmodified 5XCT3 alloy. Hence, the Nd and Sr modified alloys exhibit an important potential for improving sensitization resistance, which is mainly attributed to the lower volume fraction of β-Al3Mg2 precipitates at the boundaries due to the interruption of Al11Nd3 phase on the growth of β-Al3Mg2 precipitates and the formation of τ-Al38Mg58Sr4 phase consuming the Mg element with Sr addition during the sensitization.

Keywords

• Aluminum alloys
• Strength
• Sensitization resistance
• β-Al3Mg2 precipitates
• Nd and Sr