Properties and manufacturing characteristics of recipitation - hardening tin–magnesium bronze

Laboratory experiments and small-scale industrial trials have indicated that the optimum composition range for tin-magnesium bronze is copper, 4·60–5·25wt-% tin, 0·90–1·20wt-% magnesium, and that the most satisfactory methods of manufacturing the alloy in the wrought form are likely to be by cold working suitably heat-treated continuous-cast or hot-extruded sections. During a more detailed examination of the properties of the alloy it has been shown, for example, that after solution treatment followed by a cold reduction of 80% and final precipitation hardening, rolled strip has a tensile strength of over 800 MN/m² (113 × 10³Ibf/in², 50·5 tonf/in²), a 0·2% proof stress of about 650 MN/m² (90 × 10³ Ibf/in², 40·1 tonf/in²), a hardness of ∼270 HV, and an electrical conductivity of over 40% IACS. The resistance of this strip to stress corrosion cracking appeared to be similar to that of a cold-worked nickel-silver alloy. Some attempts have been made further to improve the properties of the alloy, but no significant improvement over the values above appears to be easily obtainable.