From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Metallurgical report concluding on casting defects and the properties of an aluminium-tin alloy.
| Identifier | ExFiles\Box 115\1\ scan0103 | |
| Date | 6th October 1936 guessed | |
| -2- Of these elements only the tin, nickel and manganese are significant in amount, the rest being impurities. The presence of nickel, suspected from the micro-structure, is confirmed. The manganese is present probably to increase ductility and hardness. It might play the same part as in Duralumin where it helps in producing fine grain. It might also help in the formation of a bearing structure. The Brinell Hardness of the bearing was 39 - 41 which compares with about 24 - 28 for white-metal and 40 for R.A.C-made lead-bronze. Conclusions. (1) A definite casting defect was found in the crack. (2) Evidence on the major crack and the presence of another crack not due to defects, suggests that cracks can start for mechanical reasons from the oil-holes. (3) The rest of the discussion in the report is speculative at this stage, especially in the absence of information from Rolls Royce as to the reasons for the composition and the somewhat nebulous state of the constitutional diagram of aluminium-tin alloys. The function of the tin is apparently that of a lubricant as even if it is present as a eutectic it melts at 229ºC. It would seem that the higher the tin content, the weaker will the alloy be at quite moderate temperatures. E.W. | ||