热挤压原位合成TiB_2/6351Al复合材料的组织性能

利用金相显微镜、扫描电镜、透射电镜和万能拉伸试验机等测试手段,研究了原位合成TiB2(wt,8%)/6351Al复合材料在热挤压前后的显微组织及室温拉伸性能。结果表明,热挤压变形有助于增强颗粒在基体合金中均匀分布,热挤压后TiB2颗粒与基体界面结合良好,未发现界面处开裂;热挤压变形时TiB2颗粒周围的基体合金中形成复杂的位错;基体合金发生再结晶和回复形成完整的等轴晶和亚结构,显微组织得到细化,基体合金再结晶的主要形核方式为增强体颗粒引起位错塞积区形核,亚晶吞并长大形核及应变诱发晶界迁移形核。热挤压复合材料基体合金具有较强的111]织构。与铸态相比,热挤压后复合材料的屈服强度Rp0.2、抗拉强度Rm、伸长率A及布氏硬度显著提高。复合材料断口特征由热挤压前的韧性和沿晶的混合断裂,转变为以韧性断裂为主。

The microstructure and properties of in-situ TiB2/6351 Al composites after hot extrusion

The microstructure and properties of the in-situ TiB2(wt,8%)/6351 Al composites before and after extrusion were studied by means of optical morphology,scanning electronic microscopy,transmission electronic microscopy and universal testing machine.The results show that hot extrusion deformation made the particles distribution more homogeneous in matrix alloy and the interface between TiB2 particles and matrix alloy is good bonding without interface cracking.During the hot extrusion deformation,the more complex dislocation structures were formed around the TiB2 particles.Recrystallization and recovery occurred,fine equiaxed grains and substructures existed in matrix and the microstructure was refined.It is noted that the accumulation of dislocations in the vicinity of TiB2 particles leading to these regions becoming sites for recrystallization nucleation,the subgain coalescent and strain-induced boundary migration(SIBM)were main recrystallization nucleation mechanism.The111] texture was formed in matrix during the hot extrusion deformation.Compared whit cast ingot,the yield strength,tensile strength,elongation rate and hardness remarkably enhance.The fracture of the cast composites displayed ductile failure and intergranular fracture.And it displayed ductile failure after extrusion.