Iranian Journal of Materials Science and Engineering

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In order to evaluate the sintering behavior of lithium meta titanate (Li2TiO3) powder, the shrinkage of powder compact was measured under constant rates of heating. Densification curves for Li2TiO3 have been constructed with the help of shrinkage powder measured at different heating rates. The activation energy at the initial stage of sintering was determined by analyzing the densification curves and the value of Q=377 kJ/mol was obtained. The diffusion mechanism at the initial sintering stage was determined by the analytical method applied to the constant rates of heating data. This analysis exhibited that the dominant mechanism for initial sintering stage of Li2TiO3 is volume diffusion from grain boundary and surfaces.

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Precipitation hardening is the most common method in the strengthening of aluminium alloys. This method relies on the decrease of solid solubility with temperature reduction to produce fine precipitations which impede the movement of dislocations. The quality control of aluminium alloy specimens is an important concern of engineers. Among different methods, non-destructive techniques are the fastest, cheapest and able to be used for all of parts in a production line. To assess the ability of eddy current as a non-destructive method in the evaluation of precipitation hardening of aluminium alloys, 7075 aluminium alloy specimens were solution treated at 480°C for 1 hr. and followed by water quenching. Afterwards, the specimens were aged at different temperatures of 200, 170, 140, 110 and 80°C for 8 hr. Eddy current measurements was conducted on the aged specimens. Hardness measurement and tensile test were employed to investigate the mechanical properties. It was demonstrated that eddy current is effectively able to separate the specimens with different aging degree due to the change of electrical conductivity during aging process

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In this work, lithium meta titanate (Li₂TiO₃) nanocrystallites were synthesized by hydrothermal method and subsequent heat treatment. The shrinkage of the powder compact was measured under constant heating rate in order to study the sintering behavior of the synthesized powders. Densification curves of the synthesized powders were also constructed via the dilatometry analysis and evaluated at several heating rates. Two separate methods of analytical procedure and master curve sintering were employed to determine the activation energy of the initial sintering stage. The activation energy values were estimated based on these two distinct methods as 229±14 and 230 kJ/mol respectively, consistenting with each other. Moreover, surface diffusion was determined as the dominant mechanism of densification on initial sintering of Li₂TiO₃ nanocrystallites.