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INTRODUCTIONThe characteristic behavior of the acoustic emission during thermoelastic phase transformations in Au-Cd alloys has previously been reported (1-3). The estimated energy of the acoustic energy was found to be approximately one order of magnitude larger during the phase transformation on heating than on cooling. No attention has been paid, so far, as to the source of the acoustic activity during martensitic phase transformations. However, it is generally accepted that the rapid release of energy within a material generates transient elastic waves of a certain amplitude and frequency content. This acoustic emission is related to the intrinsic mechanism of the martensitic transformation.Martensite formation occurs by a diffusionless shear mechanism involving the cooperative movement of a large number of atoms accompanied by a release of elastic strain energy. The thermoelastic martensite is typically athermal, where the amount of martensite depends on the formation temperature during cooling. Upon heating, the reverse transformation occurs by the backward movement of the martensitic interfaces, thus annihilating the elastic shape strains introduced during the forward transformation on cooling. The almost perfectly reversible mechanism, characterizing the thermoelastic martensitic transformation (4,5) is paradoxically accompanied by a high asymmetric acoustic energy balance (1-3).The objective of this paper is to present experimental evidence concerning the acoustic energy evolved during the heating and cooling phase changes in Au-47.5 at.% Cd polycrystals. The results are examined from the point of view of the stored elastic strain energy during the martensite formation, and the frictional work that is dissipated by the movement of martensite interfaces in either direction, upon heating and cooling (6-8). EXPERIMENTAL PROCEDURE AND RESULTSPolycrystalline specimens of Au-47.5 at.% Cd alloy were heated and cooled through the transformation temperature range, from 10°C up to 120°C and back, at controlled heating and cooling rates. A quartz rod was used as a waveguide, and coupled to a PZT transducer with a resonant frequency in the 150-300 kHz range. The experimental procedure was described elsewhere (3). Filtered signals, preamplified at a constant gain of 40 dB, were fed into an amplitude detector that characterizes the acoustic emission signals according to their peak-amplitude. Amplitude *on leave from the Materials Engineering Department, Ben Gurion University, Beer Sheva, Israel distribution, with 1 dB resolution, was then performed by a Distribution Analyzer gLV1ng a definite voltage for each channel. The amplitude distribution was chart~recorded.The correlation between the peak amplitude of the signals and the energy release at the transducer face was established by letting hardened steel balls of different mass m fall onto the quartz rod and the transducer face from different heights h. The square of the recorded peak voltage and the potential energy (E = mgh) were found to be linearly related aswh...

Surface treatments used in the daily manufacturing of parts for the automotive industry are selected to serve functional and decorative requirements achieved of mass production. Increased loads (mechanical, thermal etc.), longer life time, weight reduction, friction reduction, and corrosion resistance are demanded for modern automotive systems. Within the last decade, improved and new deposition techniques were developed in PVD, PECVD, thermochemical heat treatment and thermal spraying. These new treatments are becoming more and more common in powertrain and engine applications. Generating optimized surfaces for different types of substrate materials (e.g. Al‐ alloys, case hardened steels etc.) and geometries (e.g. bores) also impacts the running costs. Due to the new developments within these competing surface treatments, it becomes more and more common to substitute traditional treatment‐substrate‐systems with advanced treatments. Both the application potential and selected examples of different surface treatments will be shown. Aspects of the internal coating of bores inside the engine by plasma spraying, features of the corrosion protection of parts for the powertrain by the IONITOX process and piston ring treatments are discussed in more detail.

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