Microstructural evolution of semi-solid 7075 Al alloy manufactured by strain-induced melt activation (SIMA) process was investigated. The effects of different processing parameters, such as isothermal temperature and holding time on the semi-solid microstructures (the liquid volume fraction, average grain size, and degree of spheroidization of the solid particles) during partial remelting have been investigated on 7075 Al alloy that was extruded by an extrusion ratio of 20 before remelting. Experiments of remelting were carried out in the range of 560-610°C for 10, 20, and 30 min holding time and then the specimens were quenched in cold water. Microstructure of quenched samples were observed under optical microscope and then analyzed via image analysis. The results showed that high semi-solid isothermal temperature would increase the liquid volume fraction and accelerate the spherical processing of the solid particles. Furthermore at long holding time, the globular grains coarsened slightly and the average grains size are increased. The experimental results showed that the optimum process parameters, should be chosen at isothermal temperature of 580°C with the holding time, <30 min.

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The present research is the first to assess fracture of V-notches with end holes (VOnotches) made of tungsten-copper functionally graded material (W-Cu FGM) under mode I both experimentally and theoretically. W-Cu FGM specimens were fabricated by powder metallurgy technique. A number of fracture tests were carried out on VOnotched W-Cu FGM specimens under mode I for various notch tip radii, notch depths, and notch opening angles.The averaged strain energy density over a well-defined control volume was employed to predict the fracture loads. A numerical approach was used to determine the outer boundary of the control volume. Besides, the effect of notch geometry (notch tip radius, notch depth, and notch opening angle) on fracture load was elaborated. This study demonstrates that SED works well on VO-notched FGM specimens under mode I loading.

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