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Rod-like structure and microhardness during directional solidification of Sn-1wt.%Cu eutectic alloy Sn-1wt.%Cu hypereutectic alloy was directionally solidified upward at a constant temperature gradient (G=12 K · mm -1 ) in a wide range of growth velocities (V=1-250 lm·s -1 ) using an improved Bridgman-type directional solidification furnace. The microstructure was observed to be a Cu 6 Sn 5 rod in the matrix of b-Sn from the directionally solidified Sn-1wt.%Cu samples. The rod spacing (k), rod diameter (d), and microhardness (H V ) were measured from transverse sections of the samples. The experimental results showed that the rod spacing and rod diameter decreased with increasing growth velocity, while the microhardness increased with increasing growth velocity. The dependences of the rod spacing (k), rod diameter (d), and microhardness (H V ) on the growth velocity (V) were determined by using linear regression analysis, given as: k ¼ 10:49V À0:47 , d ¼ 2:1V À0:37 and H V ¼ 9:33V 0:11 , respectively. The dependences of the microhardness on the rod spacing and rod diameter were also investigated, and the relationships between them were obtained by using linear regression analysis, given as: H V ¼ 16:4k À0:235 and H V ¼ 11:8d À0:245 .