Cu-nm Of Tib <sub> 2 </ Sub> Preparation Of In Situ Composites And Friction And Wear Properties

Copper-nanosized TiBi composites were prepared by in-situ process. The microstructure, mechanical and electrical properties, and dry sliding wear behavior and electric sliding wear of Cu-nanosized TiB₂ in-situ composites was investigated; mostly task as follows:The thermodynamic data for the reactions between B and Ti in the molten liquid of copper were analyzed, the copper matrix composites reinforced by in-situ TiBi nanoparticles were prepared by reactions of 8263, carbon and titanium in copper-titanium melt, and copper-titanium, copper-boron in alloy melt, respectively, which controlled the reaction temperature, reaction time and solidification process.The rnicrostructure and mechanical and electrical properties of the in-situ composites were investigated by using optics microscope, TEM and XRD. The results showed that the in-situ formed TiBi particles which had a size of about 50nm, exhibited a homogenous dispersion in the copper matrix. Moreover, the interface between the nanoscale particles and the copper matrix was clean, and there was no certain location relationship. Due to their reinforcement, the tensile strength and hardness of the in-situ Cu-TiB₂ nanocomposite significantly improved.Dry sliding wear behavior and electric sliding wear of Cu-nanosized TiB2 in-situ composites were investigated using a pin-on-disk test rig. It has been found that TiB₂ nanoparticles improved the wear of resistance the in-situ composites. The wear rate and friction coefficient of the in-situ composites increased with increasing the applied load. Owing to the interfacial cracking which occurs under higher applied load conditions, the composite with high content of TiB₂ phase exhibited a transition from mild wear to severe wear over the applied load range from 10 N to 80 N. Under moderate applied load, Increasing the sliding speed caused a decrease in wear rate and friction coefficient of the in-situ composites because the formation of a protective oxide film occurred on the sliding surface and the hardness of the subsurface layer was maintained due toreinforcement of TiB2 nanoparticles in the Cu matrix. The predominant wear mechanisms of Cu-nanosized TiB2 in-situ composites are plastic flow and oxidational wear at higher sliding speed.Under a constant applied load and sliding speed, the wear rate of Cu-nanosized TiB2 in-situ composites was increased with increasing the electric current. The predominant electric wear mechanisms of the Cu-nanosized TiB2 in-situ composites are abrasive wear and arc erosion.