| In this paper,the casting Cu-Al-Ni-Fe-Mn aluminum bronze was used as the test material,and the effects of the new solution + two-stage aging treatment on the micro-structure and mechanical properties of aluminum bronze alloy were systemically studied.The main contents of the thesis are as follows:(1)The optimum solution temperature of Cu-Al-Ni-Fe-Mn aluminum bronze was determined by thermal analysis and micro-structure observation.The results show that the transformation point of aluminum bronze is 902.3℃;The solid solution temperature is the critical point temperature plus30~50℃,which is 902.3 ℃ +30~50℃ =932.3 ℃~952.3℃,tissue was observed in the solution temperature 940 ℃ α phase completely disappeared by the tissue observation method.The matrix is β’ phase and the solution is the most complete,thus the optimum alloy solid solution temperature is 940℃;(2)The experiment was investigated by orthogonal experiment where the first-stage aging temperature A,the first-stage aging time B,the secondary-stage aging temperature C and the secondary-stage aging time D were designed as four factors,and the tensile strength and hardness and elongation after fracture were were designed as assessment indicators.Selecting L16(45)orthogonal table for orthogonal test.The main factors influencing the tensile strength,hardness and elongation of the alloy were obtained by the analysis of the poor results.The result shows that the optimum two-stage aging treatment parameters are(200℃,2.5h)+(500℃,2.5h)The morphology and types of the precipitates were observed by scanning electron microscopy,EDS and XRD,and the mechanical properties of the alloy subjected to the optimum two-stage aging treatment and the alloy subjected to the conventional aging treatment were tested respectively.The tensile strength,hardness and elongation of the alloy treated by twostage aging treatment is 934 MPa,hardness is 239.6HB and elongation is 13.3%.CoMPared with solid solution(940℃,2h)+ aging treatment(500℃,3h),the properties were increased by10.27%,30.28% and 4.72% respectively.(3)The precipitated phase evolution process of Cu-Al-Ni-Fe-Mn aluminum bronze aftersolid solution + two-stage aging treatment was analyzed using transmission electron microscope,It is found that the precipitation phase evolution process of the alloy after two-stage aging treatment is different from that of the classical aluminum alloy.Its evolution process is: 1)partial decomposition of martensite;2)dislocation of sub-lattice formed by dislocation slip;3)the second phase nucleate in-homogeneously and precipitate on the sub-crystal boundary 4)the precipitation of the second phase is gradually growing up and spheroidizing.5)At high temperature aging condition,the alloying elements continue to precipitate on the second phase particles,which precipitated at the first-stage during low temperature aging treatment,and the second phase continues to grow.The amount of dislocation cell is related to the temperature of the formation of dislocation cell sub-grain.With the increase of temperature,the number of sub-grain increases firstly and then decreases..The more the number of dislocation cell is,there are more grain boundaries,thus the second phase nucleation position increases,leading to more number of the final precipitation and the distribution is also dispersed;on the other hand,if the number of the final precipitation of the second phase is less,the dispersion degree will decrease.In the four temperatures of 160 ℃,200 ℃,240 ℃,280 ℃,in the aging temperature of 200℃condition,there are the largest number of dislocation sub-grain in the matrix with the smallest size;The second phase of the matrix is the smallest and the dispersion degree is the highest after two-stage aging treatment.(4)The quality test of different test cycles was carried out in the condition of the load of200 N,lubrication with WA elevator oil line drops and in the condition of the load of 200 N,dry friction for 0.5h respectively using the samples subjected to the optimum two-stage aging and the conventional aging process.The test results show that the wear amount of the sample treated by the two-stage aging process is 78.2% of the sample treated by single-aging process.The morphology of the wear was observed by scanning electron microscopy.Under the condition of oil lubrication,the wear patterns of the samples subjected to two different aging processes both are abrasive wear,However,coMPared with a sample subjected to single-aging process,the furrow of the sample under the two-stage aging process is smaller,furrow edge extrusion tear phenomenon is relatively minor,positive pressure formed under the smooth area is smaller.Under dry friction conditions,the wear patterns of the two different aging processes are abrasive wear + adhesive wear + fatigue wear,and the surface wear marks are the furrow ditch,the peeling of the pit with different size and the edge of the cracks.The surface of the sample treated by the two-stage aging process is small and shallow,and it is dispersed and the edge crack is thinner.However,the surface of the sample treated by single-aging process is large and deep and the distribution is not uniform.Many pits are connected with each other and the edge cracks are also larger and the wear degree is more serious. |
