Research On Microstructure Properties Of Thrust Bearing Pedestal Of Aluminum Brass

Homogenization treatment is preceded for thrust bearing pedestal which is made of HAl60-1-1 aluminum brass by extrusion die. Microstructure and mechanical properties of each state are measured and hardness and wear resistance tests are carried out. A number of innovative research results have been made as follows:Mechanical property test is taken for aluminum brass in casting state and after extrusion forming respectively. Results show that intensity of aluminum brass after extrusion forming has been improved greatly achieving the purpose of increasing strength and other mechanical properties through warm extrusion.Hardness measurement is made for brass casting and it is found that hardness of final product is bigger than casting state but smaller than extruded samples. Through the simulation of extrusion process, we know that the radial flow of metal is small, so almost no work hardening phenomenon happens. However, lateral flow of metal occurs resulting in work hardening. The extent of work hardening is influenced by extrusion temperature, extrusion rate and deformation amount. Low extrusion temperature and high extrusion rate can make extent of recrystallization process at a low level and grain sizes as well as substructure fine. Because grain grows and substructure becomes coarse in high temperature, work hardening phenomenon can not be eliminated. This is the reason why hardness of final brass product increases but lowers than the extruded samples.Microstructure research is performed for different positions and directions of final product and the results show that organization of every part is different even in horizontal and vertical direction of the same place. According to the simulation results, we know that metal flow process differs due to different forces for different directions in the process of extrusion, so there is a difference within its internal organization. Through heat treatment experiments we also find alloy can reach the best strengthening effect when it is hold for 90min at 700℃ before quenching and then taken aging treatment for 60min at 300℃.Abrasion for HAl60-1-1 aluminum brass at the state of dry friction is studied and the experiment conclusion is that wear resistance of final product has been improved significantly compared with casting but there is still a bit disparity with extruded samples as hardness has a certain degree with wear resistance.In a word, thrust bearing pedestal of HAl60-1-1 aluminum brass through extrusion forming has been greatly improved in mechanical properties, hardness, wear resistance and so on compared with casting forming.