No abstract

No abstract

No abstract

Age hardenable Cu-1wt. % Ti-1wt. % TiB 2 composite was produced by adding boron powder to CuTi melt. TiB 2 nano particles formed via in situ reaction in the melt. This composite was aged in the temperature range 300-550 ºC for 1-25 hrs. The age hardening behavior of composite then compared with that of binary Cu-2 wt. % Ti alloy. The microstructure of the composite was examined with highresolution transmission electron microscope (HRTEM). The results of this study showed that TiB 2 particles can act as heterogeneous nucleation site for '(Cu 4 Ti) precipitates. Substantial increase in tensile and yield stress of composite (i.e. 63% and 186%) occurred relative to the solution state, after ageing at 450 ºC for 10hrs. The maximum strength was associated with precipitation of metastable Cu 4 Ti near to the ultra hard TiB 2 particles within the matrix. However the mechanical properties of composite are comparable with Cu-2 wt. % Ti alloy , the maximum value of the hardness and electrical conductivity of composite (28 %IACS , 258 HV) and Cu-2 wt. % Ti (17% IACS , 264 HV) are obtained when solution treated samples were aged at 450 ºC for 10 hrs and 15hrs, respectively.

No abstract

The joining of Al and Cu commercially pure metals using the compound casting process has been investigated where an aluminium melt is cast onto a solid cylindrical copper insert. The microstructure of the interface between copper core and surrounding aluminium was characterised by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Vickers hardness tests. Results showed that five separate reaction layers are formed in the reaction interface of core and surrounding Al. These layers included Cu9Al4, AlCu and Al2Cu intermetallic compounds; a eutectic layer; and a eutectic α-Al dendritic structure layer. Owing to the presence of hard and brittle intermetallic compounds within reaction layers, microhardness profile showed a peak of 300 HV where both parent metals have hardness <50 HV. Microhardness profile also showed that hardness decreases from the copper to the aluminium side.

Testing methods have been developed to compare the mechanical responses and failure behavior of polyetherether-keton (PEEK) thermoplastic polymer; under quasi-static, high strain rate tensile tests and fatigue loading. Tensile tests were performed with the strain rates varying from 0.0003 s −1 to 60 s −1 and at different temperatures to compare the flow characteristics of the samples undergone various testing conditions. Fatigue tests at different amplitudes and frequencies were also performed to evaluate the temperature rise during cyclic loading and its effect on the fracture behavior. Results show that dynamic tension, in comparison with quasistatic behavior, causes brittle fracture; whereas under fatigue test at high frequencies and loading amplitudes the material behaves not only a more ductile behavior but also it clearly shows the influences of induced self-heating in the modulus and mechanical properties of the PEEK were significant. So the major aim of this article is to discuss about the induced temperature and its effect on the fracture surface. Thermal fatigue has a very significant role in increasing temperature and reducing fatigue life; from there it is necessary to know the conditions at which thermal fatigue happens and also the amount of energy which is consumed. Obtained equation from the experimental results and calculations can estimate the energy dissipation in the fatigue tests which is as a function of cycle and frequency.

No abstract