Fabrication And Properties Of A Porous Cu-Based Shape Memory Alloy

The vibration and noise pollutions have seriously affected the daily life of people, whicharouses the domestic and foreign scholars to attach importance to the study on damping alloys.Cu-based shape memory alloy have its unique advantages among numerous high damping alloys.In recent years, besides using the intrinsic damping capacity, fabrication of porous materials hasbeen proved to be an effective way to further increase the damping capacity of the materials. Thepresent study aimed to further improve the damping capacity of a Cu-based shape memory alloythrough the porous approach. Damping properties were studied on the basis of exploring theprocessing conditions of the materials.A porous Cu and a porous CuAlMn shape memory alloy with adjustable porecharacteristics have been successfully fabricated by replication of NaCl space-holders viasintering-dissolution technique. Examination of macroscopic and microscopic morphologies,phase identification, as well as investigations on the compressive energy absorption and dampingproperties of the resultant materials were also carried out. The results indicated that:1. The volume fractions of pores in porous Cu range from 50 to 80% and the meandiameters range from 0.2 to 4 mm, while the volume fractions of pores in porous CuAlMn shapememory alloy range from 50 to 72% and the mean diameters range from 0.2 to 2 mm. Bothporous materials exhibit uniformly distributed and interconnected pores. Both the morphologyand diameter of pores are similar to that of the NaCl particulates.2. The compressive stress-strain curves of the porous Cu can be distinctly divided intothree stages: elasticity, plateau and densification. With increasing the porosity, the stress-straincurve decreases, resulting in shortened elastic region, prolonged plateau region and increaseddensification starting point. The compressive rates have little influence on the stress-strain curves.With increasing the porosity, the energy-absorption capacity of porous Cu decreases, while theenergy-absorption efficiency increases.3. Analysis of flexural fractograph indicates that the fracture the porous Cu specimen isdimple gliding fracture, while that of the furnace-cooled porous CuAlMn shape memory alloy is brittle fracture. After solution and quench treatment, the main fractographic appearance of theporous CuAlMn shape memory alloy is brittle and toughness4. Studies on the low-frequency damping behaviors show that the damping capacity of theporous CuAlMn shape memory alloys has been significantly enhanced compared to that of bulkCuAlMn alloy. The compressive stress-strain curves of the porous CuAlMn alloy are similar tothat of common porous metals that they can also be distinctly divided into three stages: elasticity,plateau and densification. The compressive stress-strain curve of furnace-cooled specimenexhibits serrated shape at the plateau region, showing typical characteristics of brittle porousmaterials, while the stress-stain curve of specimen subjected to solution and quench treatments israther smooth, showing typical characteristics of brittle porous materials. At the same time, thewhole curve decreases and the plateau region is prolonged.