Co-precipitation Method To Prepare Nano Al <sub> 2 </ Sub> O <sub> 3 </ Sub> Dispersion Strengthened Copper Matrix Composites Research

In the thesis, the preparation technology of nano-Al₂O₃-dispersed strengthening copper-based composites was investigated, including their structures and properties. The average size of composite powder and its distribution was analyzed by LS-800 Laser Particle Analyser and ARL/ XTAR X-Ray Diffraction; The composite structure and the appearance of powder and the wear-trace was observed by S-3000N Scanning Electron Microscope; the volume loss and 3D Microsope is tested by Micro-XAM^TM 3D Microsope respectively.The experiment scheme is that: change the maternal solution concentration, the precipitator concentration, the reaction temperature and pH, the compound powder produced by co-precipitation was analyzed by XRD, SEM and laser granular analyzer. The results showed that: the optimized reaction parameter was 55℃in 7pH with 0．095mol/L CuSO₄, 1．67g/L NH₄Al(SO₄) ₂ and 1．52mol/L NH₄HCO₃ concentration. The mean particle size of the composite powder obtained by the optimized process was about 60 nm.The nano-powder deoxided by hydrogen was then hot-pressed in order to achieve the composites with good properties, the results were as following: increase the hot pressure, improve the hot-press temperature and prolong the heat preservation time could all improve the relative density of the composites, especially the prominent effect of the hot pressure. So the optimized sintering processes were: the hot-pressed temperature was 900℃, the hot pressure was 24．5MPa, heating preservation time was 2h.Dry sliding wear behavior of Al₂O₃-dispersed strengthening copper-based composite was studied by using ball-on-surface test rig. The results showed that the friction behavior of composite was primary of adherence wear. The addition of strengthening phase improve the counter-abrasion properties of matrix, the counter-abrasion properties of copper-based composite were hoisted and then descended with the augment of porcelain content. The volume loss of composite was improved with the elevating load pressed on.The increase of the volume of ceramics will lead to increase wear-resistance and stress with the expense of decrease of the conductivity and thermal expansion of copper-based composites. The composites with good relative density will shorten the distances between grains, which will improve conductivity and wear-resistance and rupture intensity of the composites.The over-all properties of copper-based composite with Al₂O₃ 2wt% are considered to be the best, because its relative density is 92．875%, electrical conductivity is 44．2μΩ·cm, and its wear-resistance is 2．4 times of pure copper.