Study On Structure And Properties Of In-Situ Synthesized Al-Cu Alloy Prepared By Powder Metallurgy

In this paper, with the PM method, the Al-4.5%Cu alloy and three other kinds of alloy(including Al-4.0Cu-0.5Zn、A1-4.0Cu-0.5Zn-0.5Ni and A1-4.0Cu-0.5Ni) were prepared by in-situ hot isostatic pressing method from powders of Al、CuO、ZnO and Ni2O3. The density test showed that the original alloy was compacted completely. On the grain boundary of original alloy the θ-phase was separated out and in-situ synthesis Al2O3particles were produced during the sintering period, which satisfied the pre-designed objective of this project.For Al-4.5%Cu original alloy, the550℃x11h solution treatment can cause a remarkable effect. The influence of ageing treatment which followed the solution treatment on structure and properties of Al-Cu alloy was researched. It is shown that natural ageing can strengthen the alloy to a certain extent owing to the formation of GP Zone. Ageing at150℃can achieve a better effect and both the higher or lower temperature will weaken the strengthening effect. After solution at550℃for llh and aging at150℃for46h. the Al-4.5%Cu alloy has taken on advantageous mechanical properties, including high Vicker’s hardness(1300MPa), high tensile strength(328MPa), higher impact strength (72.85kJ·m-2) and elongation (6.63%). In addition, the research on the strengthening mechanism of ageing process indicates that the metastable phase such as GP zone and θ" phase formed during the earlier period of ageing process, which is the leading reason for ageing strengthening. However,these phases translated to the stable phase gradually in the later period of ageing process and the Al-Cu alloy came into "over-ageing state", which lead to some decrease on its property.Influence of heat treatment technology on structure and properties of Al-Cu-Zn、 Al-Cu-Zn-Ni and Al-Cu-Ni alloy was also investigated. It is indicated that all the three kinds alloy can be strengthened remarkably by both solution at550℃for12h and aging at150℃for40h followed. Whereas the difference on the granularity of metallic oxide and the alloy element appended resulted in some diversity of the strengthen effect between the three kinds alloy. Research on the character about the alloy ageing at150℃showed that the intervention of Zn by appending nano-level ZnO can increase the peak value of ageing curve and expedite the ageing process.and can also strengthen the alloy observably. But the intervention of Ni by appending micron-level Ni2O3can postpone the precipitation reaction during the ageing period and then slow down the speed of ageing strengthening.