| 7N01 aluminum alloy is one of the necessary materials for high-speed train. Although domestic mid-strength and weldable 7N01 aluminum alloy plate has been applied to some key components of CRH presently, the properties of them are unstable so much as they frequently can not satisfied the standard request. The cast ingot studied in this paper is 6 m long, about 8.5 t, alloy casting rod with diameter of 817 mm casted by Shandong yankuang light alloy co. LTD firtly and successfully,and this alloy casting rod is the biggest round ingot for domestic using electrolytic liquid aluminum alloy casting. In the present study, the influence of ho-mogenization on the microstructure of semi-continuous ingot and hot-rolled plate, the effect of homogenization on the properties of hot-rolled plate of domestic 7N01 aluminum alloy were studied to establish a foundation for optimizing the homogenization technique of 7N01 aluminum alloy. The main results are as follows:(1) There are mainly three kinds of constituents except the α-Al matrix phase in as-cast7N01 aluminum alloy ingot, such as many strip or blocky grayish one main comprising AlFeMnSi, a little strip or elliptical bright grayish T phase and little fine spherical black Mg2Si being inserted in the interface of T phase more often; The T phase and Mg2Si con-stituents are fully dissolved into matrix, whereas theconstituent mainly contained AlFeMnSi is partly dissolved after conventional homogenization treatment,furthermore, there are many ul-trafine dispersoid precipitated from matrix after homogenization treatment.(2) Single-stage homogenization temperature increasing from 420℃ to 470℃ has little effect on the alloy ingot excess crystalline phase,7N01 hot plate’s grain size significantly increased after solution and aging, alloy strength and elongation rates were respectively de-clining and increasing trend; with single-stage homogenization processing time extended from 12h to 36h, hot rolled plate’s solution strength and elongation were declining trend after solu-tion and aging.(3) The pretreatment before 470℃ homogenization has little effect on the alloy ingot excess crystalline phase, but the size of alloy matrix dispersed phase particle refines. With pretreatment temperature increases, the size of dispersed phase particle is smaller and smaller. However,the extension of pretreatment time has little effect on the dispersed phase particle’s size and distribution.(4)The result shows that the number of excess crystal phase after solution aging in hot rolled plates has not been changed slightly when the pretreatment temperature of ingots rises from 250℃ to 400℃, and time increases from 4h to 24h. The degree of coagulation is less decreased after extending time. Besides, bipolar homogenization treatment can refine the grain size of dispersion particles obviously in 7N01 hot rolled plates. Besides, the size of dis-persion particles increases along with the enhancement of the pretreatment temperature, but is less related to the pretreatment time.(5)Compared with the traditional ones, the strength and ductility of hot rolled plates whose ingots are under bipolar homogenization treatment are improved greatly after solution aging. The strength and even percentage elongation of alloy plates decrease when the pre-treatment temperature of ingots rises from 250℃ to 400℃. When pretreatment time increases from 4h to 24h, the strength first declines and then increases, and the ductility has not been changed slightly. |
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