Effects of Er Additions on the Microstructure, Mechanical Properties, and Electrical Conductivity of the Al‐0.4Fe‐0.05Si Alloy

Abstract

Aluminum alloy has been widely used in the fields of modern industry and high-voltage transmission due to its high specific strength, high performance-price ratio, and lightweight. The replacement of copper wire by aluminum wire has become an irreversible trend. [1-4] Fe and Si are present as impurities in aluminum alloys because the Al-Fe intermetallic is in the form of needles, flakes, and lath shapes and Si exists in the form of solid solution, which deteriorate the mechanical properties and electrical conductivity of the alloys seriously. [5-8] During the AA8011 alloy twin-roll casting process, the beta phase of AlFeSi, which has a needle-like morphology and adversely affects the formability, segregates in the center of the strip with a thickness of 10-15 μm. [9] When the addition of Al-TiC in Al-Si-Fe-Cu reaches 0.6 wt%, the average apparent length of the coarse second phase decreases to 15.37 μm. [10] The addition of Ni to Al-Fe-Si alloys can increase the electrical conductivity by 3%, but the addition of Mn and Cr will reduce the electrical conductivity by 5-10%. [11] Alloying is one of the important ways to reduce the harmful effects of Fe on the properties of aluminum alloys and improve the mechanical and electrical properties of alloys. In the recent years, a number of works have studied the effect of rare earth elements additions on precipitation strengthening and properties of aluminum alloys. [12-24] The added amount of La is even lower than 100 ppm, which can reduce the more effective heterogeneous nucleation conditions of eutectic silicon caused by P impurities. [12-14] The addition of La as low as 0.06 wt% is sufficient to achieve the ideal α-Al grain refinement, eutectic silicon modification, and improve the alloy plasticity. [12] The ultimate tensile strength (UTS) does not change with the increase in Ce concentration. [15-17] When the Ce content is increased to 0.6 wt%, the elongation of A356 alloy is improved, and the modification efficiency and elongation are the best with the content of Ce increasing to 0.1 wt%. [15] It is shown that the addition of Y leads to an increase in the thermal stability of the alloys during annealing at temperatures of 250, 300, and 370 C and removes the negative effect of the Fe and Si impurities. [18-20] Previous work has proved that the addition of Er in aluminum alloy also has a good effect on the improvement in precipitated phase morphology and properties. Zhang et al. studied the growth process and precipitation-strengthening mechanism of Al 3 Er phase in Al-0.045 at% Er alloy during isothermal aging at 300-400 C. [21] From the strength plateaus in radius of 1.4-2.4 nm, the anti-phase boundary (APB) energy of Al 3 Er precipitates was deduced to be 0.60 AE 0.03 J m À2. [21] The effect of adding Er on the crystallization properties and microstructure of Al-2 wt%Fe cast alloy by means of cooling curve thermal analysis was reported. [22] With the content of Er from 0.1 to 0.5 wt%, the supersaturated Er segregated at the α-Al/Al 3 Fe phase interface after solidifi...

Influence of cerium content on the microstructure and thermal expansion properties of suction cast Al-Cu-Fe alloys

“…Guo et al . [ 27 ] studied how Er addition into Al-Fe-Si alloy affected microstructure, phase composition, mechanical performance and electrical conductivity. According to their findings, during melting, Er (a rare earth element) removed those impurity elements Ti, V and Cr within the alloy.…”