The present invention provides a method of obtaining mechanical work from heat energy comprising heating a body of metal or metal alloy confined within a pressure vessel having a coefficient of volume expansion less than said body of metal or metal alloy contained therein to generate an increase in pressure within the vessel and causing the increased pressure to move a load thereby to do work.

A method of manufacturing a manganese steel which comprises the steps of subjecting an alloy having the following composition by weight: carbon 0.9 to 1.4%; manganese 3.0 to 8.0%; chromium 1.0 to 2.5%; molybdenum 0.5 to 2.5%; silicon 0.25 to 2.0%; cobalt 1.0 to 5.0%; with the balance iron plus incidental impurities, to heating at a temperature within the range 900.degree. to 1100.degree. C. and then cooling the alloy to a temperature below 200.degree. C. to produce a wear-resistant manganese ste...