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Abstract
Four groups of the lead-free alloys which rapidly solidified from melt were prepared. Each group contains five different alloys. These groups are: group I which was formed from Sn90Sb10-xBix, group II was formed from Sn90Sb10-xCux, group III which was formed from Sn90Zn10-xBix, and finally group V was formed from Sn90-Sb10-x-Cux, (x value ranged from 0.0-2.0 wt%). In addition, there is a quaternary group consists of two compositions Sn90Zn6Bi2Cu2 and Sn90Sb6Bi2Cu2. Studying the structural, mechanical, thermal and electrical properties of these groups of the lead-free alloys which rapidly solidified from melt were the main aim of this work. The results of x-ray differactograms spectra showed the existence of a new phase of body centered tetragonal-Sn which indicated at 2?=36.44 for Sn90Zn9.5 Bi 0.5. It could be concluded that the increase of Bi content increases the c/a ratio for the alloys under study, where, it ranged from 0.520-0.560 for all alloys under study.
The alloy hardness increased with increasing its content from bismuth (Bi). On the other hand the hardness increased with decreasing the alloy antimony (Sb) content. The maximum hardness recorded was 34.7 (107 Pa) for the alloys that have the maximum content of bismuth (2.0%) and have the lowest value of antimony (8%). The results indicated that the alloys of Sn90 Zn10-x were harder than those of Sn90 Sb10-x alloys whether that having any ratios of both Bi and Cu. where the hardness ranged from 33.5 to 43.8 107 Pa for the alloys Sn90 Zn10-x while it ranged from 31.8 to 36.8 107 Pa. Young’s modulus values of the alloys increased with increasing its content from bismuth (Bi). where, it increased from 76.0 to 110.0 GPa with increasing its content from (Cu) from 0 to 2.0% and from 76.0 to 90.0 GPa with increasing its content from bismuth (Bi) from 0 to 2.0%. The bulk modulus values increase with increasing the Bi and Cu contents of the alloys of all groups, while it decreases with increasing the Sb and Zn content of the alloys. The internal friction values of Sn-Sb-Bi alloys ranged from 60.7-84.6X10-3, and from 52.8-104.9X10-3 for the Sn-Sb-Cu alloys, while it ranged from 57.3-107X10-3 and 73.5-107X10-3 for Sn-Zn-Bi and Sn-Zn-Cu alloys, respectively.
The thermal conductivity decreases with increasing the material content of both Bi and Cu. The highest thermal conductivity values were recorded for the binary alloys where, it was 5.83 W.m-1.K-1 for Sn90Sb10 alloy and 12.79 W.m-1.K-1 Sn90 Zn 10 alloy. The average thermal conductivity values were 5.37, 6.08, 8.54 and 7.91 W.m-1.K-1, for groups I, II, III and V, respectively. The thermal diffusivity, Dth ranged from 1.19-2.60 m2/s for group I, while it ranged from 1.9-5.5, 2.9-5.7, and 2.35-5.01 m2/s for group II, group III and group V, respectively. The specific heat that were of average of 3.73, 2.69, 2.36 and 2.94 J/kg.K for groups I, II, III and V, respectively.
The electrical resistivity ranged from 26 - 30X10-8 ohm.m for Sn-Sb-Bi alloys (group I), from 24.2-26X10-8 ohm.m for the Sn-Sb-Cu alloys (group II), from 11.8-22.8X10-8 ohm.m for the Sn-Zn-Bi alloys (group III), and from 11.8-40.0X10-8 ohm.m for the Sn-Zn-Cu alloys (group V). The results indicated that the binary alloy of Sn-Sb has a resistivity value which was higher by 120% than that of the binary alloy of Sn-Zn. Also, adding bismuth has a higher effect on increasing resistivity than that of copper addition effect for both Sn-Sb and Sn-Zn alloys. The resistivity increases linearly with temperature for all alloys. By the end of test, the highest resistivity (94X10-8 ohm.m) was offered by the Sn90Zn8Cu2 alloy at 414K followed by Sn90Sb9Cu1 and Sn90Zn9Bi1 alloys with values of 73X10-8 ohm.m at 410 K. The lowest resistivity was 66X10-8 ohm.m at the end of the test (at 412K) for the Sn90Zn9Bi1.