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This paper presents the results from an experimental and theoretical analysis of the thermomechanical behaviour of a metastable P-phase single crystal alloy of composition Cu -28.3at% A1 -3.8at% Ni. The stress-strain behaviour of this single crystal material was investigated experimentally by tensile testing and this data was used to characterise the stress1 temperature martensite phase equilibria. The same alloy was also the subject of microcalorimetric measurements which enabled some of the enthalpies and entropies of transformation to be directly determined. This thermodynamic data was used to calculate the stressltemperature phase equilibria of the alloy. It is shown that the calculated equilibria agree well with those measured experimentally. It is also shown that such thermodynamic evaluations allow a direct interrogation of free-energylstressltemperature space which provides a fundamental explanation for the change in stress-induced martensite type as the temperature of the alloy is increased. It is shown that the latter is due primarily to the difference in the shear strains associated with the 0 7 ' and &-P' martensitic transformations, with a smaller effect resulting from the entropy difference between the y' and fi' phases.

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Ion implantation is an established technique for the modification of the surface characteristics of materials by bombardment with high energy ions to improve properties such as wear resistance, hardness, fatigue, and friction behaviour. The low treatment temperatures involved in this technique ensure the avoidance of distortion and are ideal for components and tools finished to a high precision. Results obtained in the present work illustrate that wear resistance and surface hardness of AISI M2, D2, and 420 steels can be improved by nitrogen implantation at doses > 1017 ions cm -2. Lubricated Falex wear tests carried out using high loads showed an enhancement in wear resistance and a significant decrease in the coefficient of friction, especially for 420 and D2 steels. Use of an ultramicrohardness technique has shown that the true hardness of implanted surface layers is greater than the values obtained by conventional micro hardness methods that result in penetration below the implanted depth. Other mechanical property data, such as elastic recovery and elastic modulus, can also be obtained from the shallow implanted layer. The results indicate that implantation of nitrogen can bring about a significant change of the near surface region of steels, promoting a change in the dominant wear mechanism and thus improving tribological behaviour of the surface.

Molybdenum disulfide (MoS2) is a popular lubricant, however a study completed in the early 1990’s stated that this type of lubricant can lead to stress corrosion cracking (SSCC) of the bolting materials. However, over the past 20 years, many bolting applications using molybdenum disulfide based compounds have been found to provide better galling resistance to the bolt assembly than many other components. It has also been shown to have a few other less desirable traits such as potential for corrosion in specific environments. Therefore, for successful bolting applications one must consider all the pros and cons of the anti-seize compound they select. One of the negative properties of molybdenum compounds is their link to SSCC on some alloys in specific environmental conditions. This paper focuses on corrosion potential.