【作者】 张继堂；

【导师】 胡明；

【作者基本信息】 佳木斯大学 ， 材料加工工程， 2008， 硕士

【摘要】 采用搅拌熔铸技术制备了原位自生Al₂O₃-TiC铝基复合材料,借助于X射线衍射仪（XRD）鉴定了该复合材料的相组成,利用扫描电镜（SEM）观察了复合材料中增强相的形貌、尺寸和分布。利用CSS-44500电子万能试验机辅以加热设备对热挤压态Al₂O₃-TiC/Al复合材料、Al₂O₃-TiC/ZL109复合材料、工业纯铝及ZL109合金等四种材料进行了高温压缩试验研究,阐述了不同温度、不同应变速率下试验材料的高温压缩行为。利用透射电镜（TEM）观察了不同压缩变形工艺后试验材料的微观组织结构演变过程,计算了不同变形工艺下的应变速率敏感指数（m ）和表观激活能（Q）,论述了高温压缩变形机制。在相同应变速率条件下,试验材料的流变应力随温度的上升而下降,在723K压缩变形时,试验材料的流变应力降低显著;在相同压缩温度条件下,试验材料的流变应力均随应变速率的提高而提高。在523K压缩时,试验材料的微观组织中都明显地出现动态回复特征;在623K压缩时,工业纯铝中动态回复现象更为明显,组织内部可以见到被拉长的亚晶晶粒,晶粒内部位错密度很低,位错沿晶界呈位错墙排布;在该温度下复合材料及ZL109合金的压缩组织中,还可以观察到明显的动态再结晶晶粒。在0.01s-1-1s-1应变速率范围内,试验材料的m值均随温度的升高而升高。在不同压缩温度范围内,试验材料存在不同高温压缩变形机制。在523K-623K压缩温度范围内,试验材料的热激活能均小于铝的晶界自扩散激活能,表明该温度范围内试验材料的变形机制是以晶内位错滑移及攀移为主要特征。而在623K-723K压缩温度范围内,各试验材料的变形机制则有所不同,工业纯铝的变形机制与其在523K-623K压缩温度范围内完全相同,而其他三种材料的表观激活能明显高于铝的晶界自扩散激活能,这表明在此温度范围内他们的变形机制是以晶界的蠕动为主要特征。更多还原

【Abstract】 The in-situ Al₂O₃-TiC/Al （ZL109） composites were fabricated by melting and casting technique. The phases in the composites were identified by XRD. The distributions and morphologies and sizes of Al₂O₃ and TiC particles were observed and determined by SEM. The compressive tests at elevated temperatures were conducted on the CSS-44500 tensile machine with a heater attached. The compressive behaviors of the composites and pure industrially aluminum and ZL109 alloy were described. The microstructures fore and after hot compressive deformation were analyzed by TEM. The sensitivity indexes of strain rate （ m ） and apparent activation energies （Q） of the test material composites at different test conditions were calculated, and deformation mechanisms were discussed at elevated temperatures.The flow stresses of the test materials decreased with temperature increasing under the same strain rate. The flow stress fell down sharply at 723K. The flow stresses increased with increasing of strain rates under the same temperature.The TEM results showed that the dynamic recovery occurred in the compressive materials at 523K. The elongated grains and few dislocations in the grains and dislocation wall along grains were seen in the pure industrially aluminum. The dynamic recrystallizations occurred near the reinforced particles and dynamic recovery far from the particles for composites and ZL109 alloy..The sensitivity indexes of strain rate increased with temperature increasing ranged from 0.01s-1 to 1s-1. There existed different deformation mechanisms at different temperatures in the materials. The thermal activation energies of all test material composites were lower than the thermal activation energy of self-diffusion of grain boundary ranged the temperatures from 523K to 623K, which indicated that the deformation mechanism were characterized by sliding and climbing of dislocations in the grains. From 623K to 723K, however, the deformation mechanisms were different. The deformation of pure industrially aluminum were same as those from 523K to 623K. And the deformation mechanism of other three material composites were characteristic of creeping of grain boundaries, for thermal activation energy of pure industrially aluminum were lower than others when the temperature was from 623K to 723K.更多还原