Neutron strain scanning of archaeological bronzes

Neutron strain scanning is a well-established experimental technique used to quantify residual stresses in industrial objects. Characteristic elastic strain profiles are introduced by manufacturing processes and by loads experienced during service. Here we report neutron strain scanning experiments on archaeological bronzes, aimed to identify their original manufacturing techniques. The specimens studied were a Picenan necklace from VI BC, and an Etruscan bucket handle from IV BC, exhibited at the Marches National Museum of Archaeology, Ancona, Italy. Time-of-flight neutron diffraction and transmission experiments were performed at the ENGIN-X instrument, Isis, United Kingdom. For the necklace, characteristic bending strain profiles and a small degree of preferred orientation indicated that the specimen has been cold worked. For the handle, broad diffraction peaks and highly distorted Bragg edges -typical of a columnar grain microstructure- suggested that this specimen was cast and did not undergo any significant thermal or mechanical treatment. The relation between the experimental diffracted and transmitted time-of-flight spectra, and the microstructure of a specimen are discussed in this paper.