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No description available.

No description available.

No description available.

No description available.

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Indium-thallium alloys in the composition range l6 to 31 at.% T1 undergo a martensitic phase transition from the higher temperature fee form to the lower temperature fct one. Certain lattice properties of these alloys have been investigated in the region of the phase boundary. The alloys studied were in single crystal form and comprised of two (11.5 and 15 at.% T1) which always had a tetragonal structure, and two (25 and 27 at.% T1) which on cooling transformed from fee to fet at 195 and 125K, respectively. Ultrasonic wave velocities and attenuation have been measured by pulse methods in the temperature range 4 to 423K (melting point 427K). In addition, thermal expansion data for the alloys have been obtained. The temperature variation of the elastic constants, determined from the sound velocity results, is discussed with reference to effects associated with the martensitic transition. One elastic constant combination - 1/2(c(_11)-C(_12)) has been shown to approach zero at the transition; theoretical calculations of elastic constants from phonon dispersion curves computed from the optimised model potential theory show a similar result, and the mechanism of the transition is interpreted as the collapse of the slow transverse acoustic phonon mode propagating in the [110] direction. Crystal stability conditions have enabled the limiting values of Poisson's ratio to be derived, and the variation of that ratio and its limits has been investigated as the phase boundary is approached. The order of the phase transition is discussed; a second order process is suggested by the results obtained.

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The wear behaviour of wear resistant alloy steels has been studied using a crossed-cylinder wear test. The wear results have been related to current theories of friction and wear established in the published literature. Wear tests have been carried out on a wide range of alloy steels sintered in vacuum to full density; in particular the following have been studied in depth: M2, M42, T15, ASP30, D2 and EN24. These alloy steels were made by the process of powder metallurgy where alloy steel powders of the co=ect =mposi tion are pressed and sintered into wear resistant engineering ccmponents . A wear test method involving a crossed cylinder abrasion test has been developed to measure the wear rates of materials with hardnesses ranging from 100-1000 VHN. The test variables studied were: time (or distance travelled), load,abrasive grit size, sliding speed and hardness of test specimens ...