The effect of pin shape on microstructure and mechanical properties of HA-Ti surface composites produced by FSP method

Titanium and Hydroxyapatite (HA) are widely used in various industries, especially medicine and implants. The friction stir welding process (FSP) is one of the best methods for the fabrication of Ti/HA surface composites.

This research specifically examines the effect of pin shape in FSP on the microstructure and mechanical properties of Ti/HA surface composites. Process parameters including pin shape (triangular, square, and conical pins), speeds of 1150 and 1250 rpm, and traverse speeds of 30 and 45 mm/min were used. Characterization of Ti/HA surface composites was performed with the help of FESEM, X-ray diffraction analysis, energy dispersive spectrometer (EDS) analysis, and tensile test.

The results of the microstructure investigation showed that the triangular pin could not enter HA powder in the titanium substrate. At a higher rotational speed, fusion occurs to a greater extent in square and conical pins, reducing defects such as holes and cracks. The ultimate tensile strength values for the square pin with traverse speeds of 30 and 45 mm/min were 772 and 605 MPa, respectively. For the conical pin with traverse speeds of 30 and 45 mm/min, they were 894 and 747 MPa, respectively. Therefore, it was found that the ultimate tensile strength decreases with increasing traverse speed in both square and conical pins. Additionally, the ultimate tensile strength is always higher in samples processed with a conical pin than a square pin. These results show that process parameters significantly affect the mechanical properties of the specimens.