Study on the improvement and mechanism of AA6101 electrical conductivity by trace TM (Zr, V, Ti) elements-assisted boron treatment

The transition metal elements (TMs) are one of the most important factors that damage the electrical conductivity (EC) of AA6101. But according to our study, during boron treatment process introducing trace TMs is beneficial to improve boron treatment efficiency and purify the Al matrix. In this work, boron treatment and TM-assisted composite boron treatment are carried out to improve the EC of AA6101 and the influence mechanism of TMs (Zr, V, Ti) on boron treatment is studied in detail. Results show that the EC of AA6101 improves and then decreases with the increasing of B addition, reaching a maximum value of 53.4% International Annealed Copper Standard (IACS) with 0.09% B (all compositions quoted in this work are in wt% unless otherwise stated). But by analyzing the boron reaction products, it can be found that the TM borides are core-shell structure and the core mainly is unreacted AlB2 compounds, thus the boron treatment efficiency is relative low. Based on this, besides 0.09% B addition, different amounts of TMs (Zr, V, Ti) are introduced into Al melts to break the core-shell structure and promote the boron reaction going on. When the additions of Zr, V, and Ti are 0.05%, 0.06%, and 0.03%, the EC of AA6101 can reach 54.2%IACS, 53.9%IACS, and 53.7%IACS, respectively. By comparing it is obvious that Zr-assisted boron treatment is the best and the EC of AA6101 is 8.2% better than AA6101 without treatment (50.1%IACS). On the basis of thermodynamics and dynamics, Zr can replace the TMs on the boride particles, and the replaced TMs continue to react with the unreacted AlB2 in the boride center. Thus more TMs impurities are involved in the reaction and their damage to EC of AA6101 can be reduced. At last, a schematic diagram is drawn to explain the influence mechanism of TMs on boron reaction process, which is useful for the development of conductive Al alloys.