A Novel Powder Metallurgy Processing Approach to Prepare Fine-Grained Cu-Al-Ni Shape-Memory Alloy Strips from Elemental Powders

The current work describes the experimental results related to the successful preparation of fine-grained Cu-Al-Ni high-temperature shape-memory alloy (SMA) strips from elemental Cu, Al, and Ni powders via a novel powder metallurgy (P/M) processing approach. This route consists of short time period ball milling of the elemental powder mixture, preform preparation from milled powder, sintering of preforms, hot-densification rolling of unsheathed sintered powder preforms under a protective atmosphere, and postconsolidation homogenization treatment of the hot-rolled strips. It has been shown that it is possible to prepare chemically homogeneous Cu-Al-Ni SMA strips consisting of equiaxed grains of average size approximately 6 µm via the current processing approach. The finished SMA strips were almost fully martensitic in nature, consisting of a mixture of b'1- and c'1-type martensites, and exhibited excellent mechanical properties, including an average fracture strength of 677 MPa and a 13 pct average fracture strain. The Cu-Al-Ni strips demonstrated almost 100 pct one-way shape recovery after bending followed by unconstrained heating at various pre-strain levels, indicating promising characteristics for potential applications in automotive and aerospace industries.