Processing and Characterization of Cu-Al-Ni Shape Memory Alloy Strips Prepared from Prealloyed Powder by Hot Densification Rolling of Powder Preforms

Abstract

The present work deals with the preparation of near-full density Cu-Al-Ni shape memory alloy (SMA) strips from argon-atomized prealloyed powder via a powder metallurgy (PM) route comprising cold die compaction to prepare powder preforms, sintering, and hot densification rolling of unsheathed sintered powder preforms under protective atmosphere at 1273 K (1000°C). It has been shown that argon-atomized spherical Cu-Al-Ni SMA powder consisted of very fine equiaxed grains and no appreciable grain growth occurred during sintering at 1273 K (1000°C). It also has been shown that no appreciable densification occurred during sintering, and densification was primarily achieved by hot rolling. The densification behavior of the sintered powder preforms during hot rolling was discussed. The hot-rolled Cu-Al-Ni strips were heat-treated at 1223 K (950°C) for 60 minutes and water quenched. The heat-treated strips consisted of equiaxed grains with average size approximately 90 lm. The heat-treated Cu-Al-Ni SMA strips consisted of self-accommodated b 0 1 martensite primarily, and showed smooth b 1 ) b 0 1 transformation behavior coupled with a very low hysteresis (%25 K (25°C)). The heattreated strips exhibited an extremely good combination of mechanical properties with fracture strength of 530 MPa and 12.3 pct fracture strain. The mode of fracture in the finished strip was primarily void-coalescence-type ductile together with some brittle transgranular type. The shape memory tests showed almost 100 pct one-way shape recovery after 100 bending-unconstrained heating cycles at 4 pct applied prestrain, exhibiting good stability of Cu-Al-Ni strips under thermomechanical actuation cycling. The two-way shape memory strain was found approximately 0.45 pct after 15 training cycles at 4 pct training strain.

Production and Mechanical Properties of Cu-Al-Ni-Be Shape Memory Alloy Thin Ribbons Using a Cold Co-Rolled Process

“…This diffractogram shows many peaks suggesting a multi-phase alloy. In this diffractogram, there are the peaks of the Al, the peaks of CuNi [14,44], the peaks of NiAl [45,46] and those of the austenite phase of the Cu-based SMAs [47,48].…”

“…Thus, their disadvantages have restricted the use of these alloys for commercial applications in particular in SE applications. One way to solve these problems is to refine the grain of the CuAlNi SMAs by adding some alloying elements such as Be or by varying the compositions of Ni and Al [12][13][14]. These changes have shown some improvement in mechanical properties.…”

Preparation of Cu–Al–Ni shape memory alloy strips by spray deposition-hot rolling route

“…It has been demonstrated that powder metallurgy (PM)-based processing approach is an effective technique to achieve fine-grained Cu-Al-Ni alloys with high strength and reasonable ductility [23][24][25][26][27][28][29][30]. Most of the PM-based approaches involved either elemental or pre-alloyed powders as starting material followed by their consolidation via different methods to prepare bulk material of different shapes and sizes.…”

Effect of Ta Additions on the Microstructure, Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys

“…Several investigations have aimed to develop fine-grained Cu-Al-Ni alloys, with a grain size considerably less than 100 μ m, by using various powder metallurgy techniques [ 13 , 14 ]. These kinds of techniques depended on the Cu-Al-Ni alloy powder, which was prepared by either an inert gas atomization process or mechanical alloying of elemental powders in a high-energy ball mill under inert gas atmosphere [ 15 ]. The mechanical alloying (MA) method [ 16 , 17 ] is one of the most desired methods; it is indeed reported to be more affordable and also convenient for manufacturing applications.…”