Investigation of the wear resistance of in-situ Al-Ti composites fabricated by mechanical alloying and hot extrusion

In this research, the wear behaviour of Al-20%Ti composites, fabricated by mechanical alloying and hot extrusion at different conditions, was investigated using the pin-on-disc method. A high-energy vibratory mill was applied to produce the nanocomposite (Al-20Ti-4hrV) and nanocrystalline (NC) Al samples, while a low-energy planetary mill was used to produce the other composites (Al-20Ti-20hrP and Al-20Ti-60hrP). To examine the microstructure and worn surface of specimens, optical microscopy and scanning electron microscopy were performed. To estimate the mechanical properties of the samples, their density and Brinell hardness were measured. The use of a high-energy vibratory mill caused the formation of an ultrafine aluminium matrix with in-situ nanometric intermetallic particles in the Al-20Ti-4hrV sample. As a result, the highest relative density and hardness and the best wear resistance were obtained in the Al-20Ti-4hrV sample. The application of the low-energy planetary mill led to the formation of flaky particles; accordingly, low relative density, poor mechanical properties and wear resistance in Al-20Ti-20hrP and Al-20Ti-60hrP samples were observed. The dominant wear mechanisms for Al-20Ti-4hrV and NC Al samples were identified as microploughing, adhesion and oxidation in the mild wear regime, whereas those of the Al-20Ti-20hrP and Al-20Ti-60hrP samples were mainly adhesion wear mechanism and inconsiderable delamination in the mild wear regime. The highest hardness and wear resistance were obtained for the nanocomposite sample owing to nanometric Al3Ti reinforcement, nanocrystalline Al matrix and good adhesion between particles and the matrix. This study confirmed that the nanocomposite production method presented in this research is suitable for wear-resistance applications.