Microstructure and Properties of Mn-Cu-Based Damping Alloys Prepared by Ball Milling and Hot-Press Sintering

A Mn-Cu-based damping alloy with a nominal composition of 70Mn-24Cu-3Zn-3Al (at.%) was prepared by ball milling of pure elemental powders and subsequent hot-press sintering of powder mixture at 750 and 825 degrees C for 2h. For comparison, this alloy was also prepared by induction melting technology and then homogenized at 850 degrees C for 24h. Further, they were aged at 430 degrees C for 2h. The microstructure, damping capacity and microhardness of the hot-press-sintered and induction-melted alloys have been investigated. The results show that the microstructure of the powder mixture upon ball milling mainly comprises convoluted composite particles containing alpha-Mn and gamma-Cu phases, and isolated alpha-Mn ones around. The high compactness of the alloys is obtained after hot-press sintering (94.8 and 98.6% at 750 and 825 degrees C, respectively). At a holding temperature of 750 degrees C, the microstructure of the alloy is primarily composed of gamma-MnCu, gamma-CuMn and alpha-Mn grains. With increasing the target temperature to 825 degrees C, the single gamma-MnCu solid solution has been formed in the alloy by diffusion of Mn etc. into gamma-Cu lattices. The hot-press-sintered alloys (especially at 825 degrees C) possess relatively high damping capacity although which is still lower than that of induction-melted one. In contrast, the microhardness of the hot-press-sintered alloys (especially at 750 degrees C) is obviously higher than that of the induction-melted one.