Abstract
The technical viability of preparing a Cu-Al-Nb shape memory alloy by high energy ball milling in a planetary mill has been evaluated. The alloy Cu-13Al-2Nb (wt. (%)) was prepared by mixing pure elemental powders. A ball-to-powder weight ratio of 6:1 and rotation rate of 150 rpm in argon atmosphere were the main processing parameters. The milling time ranged from 1 to 65 hours. Changes in microstructure as a function of milling time were investigated, using X-ray diffraction analysis and scanning electron microscopy. To investigate the viability of producing sintered parts from milled powders, the conventional powder metallurgy route was used. The milled powders were compacted in a cylindrical die at 900 MPa. Sintering was carried out in argon atmosphere at 850 °C for 6 hours. This study has shown that high energy ball milling, combined with pressing and sintering, can be used to promote the formation of a copper-aluminum solid solution and achieve final sintered densities of 91% of the theoretical density.
Highlights
Shape memory alloys (SMA) are conventional functional materials with intrinsic characteristics that differentiate them from other materials
A planetary ball mill Fritsh Pulverisette® with four stainless steel vials was used in the mechanical alloying (MA) process
These peaks marked with X coincide with the peaks of orthorhombic martensite 2H, suggesting that these could be of a martensitic structure induced by deformation during the milling process[4]
Summary
Shape memory alloys (SMA) are conventional functional materials with intrinsic characteristics that differentiate them from other materials. The main characteristic of these materials with shape memory effects is diffusionless phase transformation (martensitic transformations). Among Cu-based SMAs, the CuAlNb system has better thermal stability[1]. High energy planetary ball milling was used to convert the Cu-Al-Nb elemental powder mixture into pre-alloyed powders. The purpose of this investigation is to evaluate mechanical alloying as a process to obtain Cu-Al-Nb alloys with shape memory effects, with or without the addition of lubricants
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