Abstract: Internal friction measurement serves as an important means for studying the damping properties of materials and the dynamic evolution of their microstructure, which is of critical significance for engineering vibration reduction design and material development. To address the issues of weak driving force and limited amplitude range in existing internal friction testers when measuring high-stiffness materials, this study systematically improved the MFP-1000 low-frequency torsional pendulum internal friction apparatus. By designing a thickened vertical pendulum rod, optimizing the magnetic circuit layout, and enhancing the coil driving capability, the maximum output amplitude and torque capacity of the system were significantly improved. Using the upgraded setup, systematic tests were conducted on the internal friction behavior of two damping alloys, (Cu-Al-Mn and Cu-Al-Mn-Ce) under different strain amplitudes, temperatures, and frequencies. The results show that the modified system enables stable measurement at larger amplitudes. When the amplitude exceeds 10⁻³, the internal friction exhibits nonlinear behavior, first decreasing and then increasing. Both alloys display an internal friction plateau within the 25~350℃ range, and reverse martensitic transformation internal friction peaks are observed at 443℃ and 452℃, respectively. The internal friction values of both alloys increase with frequency, showing an initial rapid rise followed by a slower increase. The addition of Ce leads to significant refinement of grains and martensitic structures, increasing interface density, and thus the Cu-Al-Mn-Ce alloy demonstrates superior damping performance. This research provides a reliable experimental platform for internal friction testing of materials under wide amplitude, high/low temperature, and variable frequency conditions, offering important support for the development of high-performance damping alloys and the advancement of engineering vibration reduction technologies.