Determination of Dynamic Friction Coefficients of Aluminum Alloys at Elevated Temperatures by Using Ring-Compression Tests
Li-Fu CHIANG, Noriaki NISHIOKA, Jian-yih WANG, Hiroyuki HOSOKAWA, Tokuteru UESUGI, Yorinobu TAKIGAWA and Kenji HIGASHI
Abstract:The dynamic friction coefficients of the commercial aluminum alloys (A2014, A2024 and A6061) and a superplastic IN9021 alloy were measured by ring-compression tests in a temperature range from 573 to 753 K and a stain rate range from 1.0 x 10-2 to 4.0 x 100 s-1. In general the friction coefficients (m values) increase slightly with increasing the compressive strains even under the well-lubricated test conditions. The m values of the Al-Cu based alloys, including A2014, A2024 and IN9021, were almost same at 0.2 ` 0.4 at the temperatures below 723 K, but increased rapidly at the temperatures above 723 K. On the other hand those of A6061 were almost constant at about 0.4 at the temperatures below 753 K. The analysis based on the constitutive equation with consideration of the effect from an existence of the particles indicated that the dominant deformation mechanisms under the investigated conditions were dislocation creep for A2014, and were superplasticity for IN9021 except for the test condition at 573 K with 1.0 x 10-1 s-1. The m values of the IN9021 were lower than those of A2014, even if the flow stresses of IN9021 were higher than those of A2014. So it was concluded that the m value under a superplasticity region was lower than that under a dislocation creep region. It suggested that the superplastic forming had more benefits for the engineering applications. Key Words:Forging, Friction, Aluminum alloy, Elevated temperature, Compressive testing and deformation mechanisms