【作者】 尹奎波；

【导师】 边秀房；

【作者基本信息】 山东大学 ， 材料加工工程， 2005， 硕士

【摘要】 Al-Mg合金具有低密度、高比强度的优点,因而在工业生产中具有广阔的应用前景。本文以Al-10Mg合金为对象,系统研究了三类细化剂对Al-10Mg合金的晶粒细化行为,以及细化处理对合金性能和合金中p（Al₃Mg₂）相含量的影响。 利用高倍视频显微镜、电子探针、扫描电镜等测试手段研究了细化剂对Al-10Mg合金的细化特征。实验结果显示:Al-5Ti-1B、Al-5Ti-0.25C和Al-Ti-C-Ce三种中间合金对Al-10Mg合金均有良好的细化效果。加入0.1%Al-5Ti-1B可使合金晶粒尺寸由650μm细化到62μm;加入0.2%Al-5Ti-0.25C后合金平均晶粒尺寸可变为71μm;加入Al-Ti-C-Ce（加入量相当于0.2%Al-5Ti-0.25C+0.2%Ce,下同）可使合金晶粒尺寸降为80μm。随着保温时间的延长,三种细化剂均出现细化衰退现象,其中Al-5Ti-0.25C中间合金细化衰退现象较严重,而Al-Ti-C-Ce中间合金最轻。 通过显微硬度计测定了合金细化前后的显微硬度。实验结果表明:细化处理能显著提高合金的显微硬度,加入0.1%Al-5Ti-1B可使显微硬度提高9.2%,加入0.2%Al-5Ti-0.25C可提高12.6%,而加入Al-Ti-C-Ce可提高10.3%,可见加入Al-5Ti-0.25C能更有效的提高合金的显微硬度。 通过膨胀计测定了合金细化前后的热膨胀系数。实验结果显示:细化处理降低了合金的热膨胀系数。同时,与加入0.1%Al-5Ti-1B相比,加入0.2%Al-5Ti-0.25C中间合金细化的Al-10Mg合金具有更小的热膨胀系数,而加Al-Ti-C-Ce细化后的合金热膨胀系数与加Al-5Ti-0.25C的基本相同。 通过差示扫描量热仪（DSC）测定了合金细化前后的升温曲线和降温曲线。实验结果发现:升温曲线中第一峰的面积可用来表征Al-10Mg合金中β相的相对含量,加入0.1%Al-5Ti-1B和加入0.2%Al-5Ti-0.25C均能使第一峰面积大幅减小,而加入Al-Ti-C-Ce使第一峰面积增大。β相含量降低说明更多Mg以固溶原子形式存在于α-Al中,这对提高合金强度有重要作用,同时将使合金固溶处理时间缩短。 DSC降温曲线表明:加0.1%Al-5Ti-1B可使Al-10Mg合金共晶反应放热峰的面积大幅度减少,而加入0.2%Al-5Ti-0.25C,共晶反应放热峰完全消失,说明更多还原

【Abstract】 Al-Mg alloys are of great potential as structural materials for their appreciated properties, such as low density and high specific strength. In the present paper, the grain refining performances of various refiners have been studied systematically on Al-10Mg alloy. The effects of grain refinement process on mechanical properties and the relative content of β （Al₃Mg₂） phase have also been discussed.The grain refining performances of various refiners on Al-10Mg alloy have been investigated using HSVM, EPMA, and SEM, etc. It has been found that there are effective grains refining efficiencies in Al-10Mg alloy after addition of A1-5TMB, Al-5Ti-0.25C, and Al-Ti-C-Ce master alloy. The grain size changes from 650μm to 62μm with 0.1% addition of Al-5Ti-lB, while it reaches 71μm with 0.2% addition of Al-5Ti-0.25C and reaches 80μm with addition of Al-Ti-C-Ce（its additional level is equal to 0.2% Al-5Ti-0.25C+0.2%Ce, the same to the following）. The grain size with holding time has an ascending trend in all the three refiners, of which the decline with addition of Al-5Ti-0.25C is more serious and the decline with addition of Al-Ti-C-Ce is the better.The microhardnesses of Al-10Mg alloys have been studied and the results show that grain refinement process could improve the microhardnesses of Al-10Mg alloys. It is increased by about 9.2% after 0.1% addition of Al-5Ti-1B master alloy and about 12.6% after 0.2% addition of Al-5Ti-0.25C master alloy and 10.3% after addition of Al-Ti-C-Ce. Therefore it is more effective to improve the microhardness with addition ofAl-5Ti-0.25C.The dilatometric coefficients of Al-10Mg alloys have been investigated using dilatometer. The dilatometric coefficients decrease after additions of the refiners. Al-5Ti-0.25C makes the dilatometric coefficient of Al-10Mg alloy lower than A1-5TMB and the dilatometric coefficients with addition of Al-Ti-C-Ce are equal to those with addition of Al-5Ti-0.25C in general.The heating curves and the cooling curves before and after addition of refiners have been studied by differential scanning calorimeter （DSC）. It has been found that the first peak area in the heating curves is the token of the relative content of P phase. The area decreases with addition of Al-5Ti-lB and Al-5Ti-0.25C refiners, however, it increases with addition of Al-Ti-C-Ce refiner. The reduction of the relative content of P phase shows that more Mg would exist in the form of solid-resolve atoms, which can improve alloy intensity and reduce the solid-resolve process time.In the DSC cooling curves of Al-lOMg alloys, the area of eutectic reaction peak decreases seriously after addition of 0.1% Al-5Ti-lB and it disappears after addition of 0.2% Al-5Ti-0.25C, which shows that Ti could increase the coefficient of distribution of Mg. The eutectic reaction peak width increases and its area is almost equal to that of the unrefined Al-lOMg alloy after addition of Al-Ti-C-Ce. The refiners also have some effects on the characteristic temperatures in the DSC cooling curves.According to the Hall-Petch equation, the relationship between microhardness and grain size is calculated in Al-lOMg alloys with various refiners. When we have measured one factor, the other could be obtained by calculation, which greatly reduces the hard work.更多还原