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Nanostructuring, morphology tuning, doping, as well as alloying have decisive roles in controlling the performance of functional materials.

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The stationary shoulder friction stir welding (SSFSW) technique promotes new opportunities for welding material. In the current work, a special setup of SSFSW was designed and manufactured in only three parts according to the homemade friction stir welding (FSW) machine dimensions and specifications. This setup with minimum parts is easily adjustable beside it facilitates fast control of the tool pin length. This gives the design more advantages than the previous designs published for the same purpose. Two different parameters were used with the SSFSW setup to butt weld samples of AA7075-T6 of 5 mm thick. Various welding travel speeds of 25, 50 mm/min to 75 mm/min and different values of Z-force of 20, 25 KN, and 50 KN were used to evaluate the effect of the SSFSW parameters on the joints quality and properties. The results confirmed that sound joints were produced without internal or surface defects. In addition, the joints are characterized with a smooth surface finish compared to the conventional FSW joints. A narrow heat affected zone around the nugget due to the elimination of heat generation by the shoulder. The tensile strength of welded samples increases with increasing the vertical force with the maximum tensile strength of 418.7 MPa at a rotational speed of 600 rpm, a welding speed of 50 mm/min, and 50 KN Z-force. This implies that the vertically applied force upon SSFSW is an important parameter in controlling the joint properties. Analysis of the hardness distribution across the weld cross-section shows a slight reduction in the heat-affected zone.

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The mode I fracture toughness of fully pearlitic eutectoid steel used in the transportation industry has been investigated at temperatures ranging from 2196 to 225uC using bend bar specimens notched and fatigue precracked to contain different root radii. The effects of changes in microstructure on the cleavage fracture stress were determined over a similar range. In addition, the notched and fatigue precracked specimens have been subjected to combined mode I/II fracture under asymmetric three point bend loading at 2125uC on different microstructural conditions. Increasing the offset distance between the notch and the loading point produces an increase in the ratio mode II/mode I, a change in the crack deflection angle and a reduction in the total energy of fracture. Significant effects of changes in microstructure, test temperature and notch root radius on the toughness will be presented, followed by the significant effects of changes in microstructure and the ratio mode II/mode I on the fracture load, crack deflection angle and resulting toughness. Fractured specimens were examined both macroscopically and microscopically using stereomicroscope and scanning electron microscopy.

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