摘要
直接电解加钛是一种新的加钛方式,这种方式得到的低钛铝合金不仅生产工艺简单、生产成本低而且具有很好的晶粒细化效果。钛含量越高经济效益越显著,但直接电解生产钛含量高于1%的低钛铝合金在技术上还是有很大困难的。对于直接电解的较高钛含量(0.3% 本文探索以直接电解获得的低钛铝合金(Ti0.6%)为原料,利用高温保温,通过铝钛偏析使低钛铝合金偏析成钛含量更低的符合国家标准能作为母体材料使用的低钛铝合金和钛含量更高的能作为中间合金使用的高钛铝合金。本文对偏析的影响因素进行了系统的研究,本文的研究内容主要包括以下几个方面。
首先,研究了直接电解的低钛铝合金的铝钛偏析的可行性、偏析的影响因素及偏析后的微观组织。结果表明,在合适的温度下保温一段时间,低钛铝合金有明显的偏析现象,可以偏析成含钛量不等界线分明的两部分；在700℃保温时含钛相的偏析主要受熔体粘度的控制,随着时间的增加偏析效果改善；在750℃保温时,含钛相偏析受熔体粘度、扩散和平衡浓度的共同作用,温度升高粘度减小,偏析程度改善,由于平衡浓度的升高,偏析效果又开始减弱；在800℃保温时,熔体的粘度小,扩散作用强,扩散充分,随着时间的增加偏析效果变化很小,由于此时平衡浓度较高,偏析效果没低温时好；偏析后的上部的低钛合金中,钛元素主要以固溶体的形式分布在铝基体中,在偏析后的下部的高钛合金中,A13Ti相主要以丝状和棒状的形式存在。
另外,对低钛铝合金的偏析工艺进行了研究,并对比研究了偏析后两部分含钛合金和直接电解的低钛铝合金以及Al-5Ti中间合金对工业纯铝的细化效果。结果表明,直接电解的含钛量为0.6%的低钛铝合金在750℃保温60min可取得较好的偏析结果,偏析后得到的上部低钛合金的钛含量为0.2%-0.3%可以作为母体材料使用,下部高钛合金钛含量为2%-3%可以作为中间合金使用；偏析后的两部分合金对纯铝都有良好的细化效果,其细化能力和直接电解的低钛铝合金以及A1-5Ti中间合金的细化能力相当,偏析没有减弱原合金的细化能力,合金的细化能力得到了保持。
Titanium addition by electrolysis is a new technology of producing aluminum containing low content titanium. This method has lots of advantages, such as simple production technology, low cost, excellent grain refinement effect and so on. The higher titanium content, the more significant economic benefits, but it is still very difficult in technology to produce low-titanium aluminum alloy which contain titanium more than 1% by electrolysis. The promotion of low-titanium aluminum alloy with high titanium content (0.3% In this paper, low-titanium aluminum alloy (Ti0.6%) produced by electrolysis was served as raw materials. Method of high temperature insulation was adopted, and the low-titanium aluminum alloy was divided into low-titanium aluminum alloy with lower titanium content which can meet the national standard and be used as the matrix material and low-titanium aluminum alloy with higher titanium content which can be use as a master alloy through the segregation of aluminum and titanium. In this paper, the feasibility of this approach was explored, and the factors that influence the segregation were investigated systematically. This study mainly include the following contents:
First, the feasibility of segregation of the low-titanium aluminum alloy produced by electrolysis was investigated. After segregation, the variation of volume and mass ratio of the lower part of low-titanium aluminum alloy with temperature and time was investigated. In addition, the microstructure morphology of the sample after segregation was observed. The results show that low-titanium aluminum appears obvious segregation, and obvious dividing line appears between the two parts of the alloy after insulation with different temperatures and times; For the insulation at 700℃, the segregation of titanium phase is mainly affected by the melt viscosity and the segregation effects can be improved by increasing the insulation time.; For the insulation at 750℃, the segregation of titanium phase is affected by melt viscosity, diffusion and equilibrium concentration:increasing the temperature can improve segregation due to the decreasing of the viscosity, but, the effect of segregation decline again because the improvement of the equilibrium concentration; For the insulation at 800℃, the melt viscosity is small, the diffusion is strong and fully, the segregation effect changed very little when increasing segregation time, the equilibrium concentration is higher, the segregation effect is not as good as that of low temperature; After segregation, Ti mainly distributed in the Al matrix in the form of solid solution for the low-titanium alloy of the upper part, and for the lower part of the high-titanium Alloy, Al3Ti distributed in the form of filamentous and rod.
In addition, the industrial feasibility of segregation was simulated. Effect of two parts of low-titanium aluminum alloy with segregation, low-titanium aluminum alloy without segregation produced by electrolysis and Al-5Ti master alloy on the commercially pure aluminum refining was compared and investigated. The results show that the best segregation result was obtained in the insulation temperature of 750℃and insulation time of 60min for the low-titanium aluminum alloy of Ti0.6% produced by electrolysis. After segregation, the upper part of low-titanium alloy has titanium content of 0.2%～0.3% which can be used as a matrix material, the high-titanium has titanium content of 2%～3% which can be used as an master alloy; Both of the two parts of low-titanium aluminum alloy with segregation have desirable refining effect on the commercially pure aluminum, and its refining capacity is comparable to the low-titanium aluminum alloy without segregation produced by electrolysis and Al-5Ti master alloy; segregation has not diminished the refining capacity of the original alloy, and the refining capacity has been maintained.
引文
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