4D printing of Ni–Mn–Ga magnetic shape memory alloys: A review

4D printing has grown tremendously in the last decade, enabling functional structures made of smart materials to be manufactured. Current metal 4D printing research has focused on thermal shape memory alloys (SMAs) and to a lesser extent on magnetic SMAs. This review assesses the progress in 4D printing of Ni–Mn–Ga, highlighting the key challenges and opportunities for applications. The mechanism of the magnetic SMAs and the influence of 4D printing process parameters on the microstructure and material properties are explored, with an emphasis on laser powder bed fusion processing. Control of porosity, microstructure, texture and impact of post-processing on magnetic performance are the key challenges for the development of Ni–Mn–Ga 4D printing.