Effect of UNSM on Hardness and Microstructural Evolution of Cu-Sn Alloy

What is it about?

In this study, a Cu-Sn sintered bronze, used largely for con-rod bushing and automotive transmission, was treated by ultrasonic nanocrystalline surface modification (UNSM). Then, Vickers hardness and microstructural evolution of the treated region were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The hardness of the treated surface doubled, which is attributed to the developed of nano-scale grains, deformation twins, and high density of dislocations induced by the UNSM. Microstructural modification beneath the UNSM treated surface was typically characterized with increase of the depth: (i) nano-scale grains (top surface), (ii) intersection of deformation twins (~30 µm), (iii) high density nano-scale twin/matrix lamellae (~50 µm), (iv) interception of micro band and deformation twins (~100 µm), (v) dislocation arrays (~200 µm), (vi) low density dislocations (~300 µm) and (vii) pre-existing coarse grains and annealing twins in unaffected region (400 µm ~deeper).

Featured Image

Why is it important?

In this study, a Cu-Sn sintered bronze, used largely for con-rod bushing and automotive transmission, was treated by ultrasonic nanocrystalline surface modification (UNSM). Then, Vickers hardness and microstructural evolution of the treated region were investigated by using scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The hardness of the treated surface doubled, which is attributed to the developed of nano-scale grains, deformation twins, and high density of dislocations induced by the UNSM. Microstructural modification beneath the UNSM treated surface was typically characterized with increase of the depth: (i) nano-scale grains (top surface), (ii) intersection of deformation twins (~30 µm), (iii) high density nano-scale twin/matrix lamellae (~50 µm), (iv) interception of micro band and deformation twins (~100 µm), (v) dislocation arrays (~200 µm), (vi) low density dislocations (~300 µm) and (vii) pre-existing coarse grains and annealing twins in unaffected region (400 µm ~deeper).