热处理对Al_(2)O_(3f)/Mg-6Al-1Nd-1Gd复合材料组织演变与蠕变性能的影响

Effect of Heat Treatment on Microstructure Evolution and Creep Properties of Al_(2)O_(3f)/Mg-6Al-1Nd-1Gd Composites

采用光学显微镜、扫描电镜、X射线衍射仪、EDS能谱分析等手段研究了不同热处理态Al_(2)O_(3f)/Mg-6Al-1Nd-1Gd复合材料在200℃、70MPa条件下压缩蠕变前后金属间化合物的变化情况以及蠕变性能差异。结果表明:Al_(2)O_(3f)/Mg-6Al-1Nd-1Gd复合材料中的金属间化合物主要可分为β-Mg_(17)Al_(12)、Al_(2)(Nd,Gd)、Al_(11)(Nd,Gd)_(3)和Mg_(2)Si四种。复合材料经420℃+24h固溶处理后,β-Mg_(17)Al_(12)相和Al_(11)(Nd,Gd)_(3)相几乎完全消失,而经T6处理后,又会重新析出。其中,β-MgAl_(12)相呈针状或块状弥散分布于晶内,而Al_(11)(Nd,Gd),相则呈针状或短棒状在纤维周围或晶界处偏聚。与铸态和T6态复合材料相比,T4态复合材料组织中Al_(2)(Nd,Gd)相和Al_(11)(Nd,Gd)_(3)相分布最为均匀,不会因针状Al_(11)(Nd,Gd)_(3)相在纤维处的偏聚而影响到复合材料界面应力传递,高温抗蠕变性能最佳,最大蠕变应变值和稳态蠕变速率分别为0.5%和6.94×10^(-9)s^(-1),相比铸态复合材料分别下降了54.5%和58.4%。

The change of intermetallic compounds and the difference of creep properties of Al_(2)O_(3f)/Mg-6Al-1Nd-1Gd composites before and after compression creep at 200℃ and 70 MPa were studied by optical microscopy,scanning electron microscopy,X-ray diffractometer and energy dispersive spectroscopy.The results showed that the intermetallic compounds in the Al_(2)O_(3f)/Mg-6Al-1Nd-1Gd composites were mainly divided into β-Mgi_(7)Al_(12),Al_(2)(Nd,Gd),Al_(11)(Nd,Gd)_(3) and Mg_(2)Si.After solution treatment at 420℃+24 h,the(-Mg_(17)Al_(12)) and Al_(11)(Nd,Gd)_(3)phases almost disappeared completely,while T6 treatment precipitated again.The(-Mg_(17)Al_(12)) phase was needle-like or massive diffusely distributed in the grain,while the Al_(11)(Nd,Gd)_(3) phase was needlelike or short rod shaped and clustered around the fiber or at the grain boundary.Compared with the as-cast and T6 composites,the Al_(2)(Nd,Gd)and Al_(11)(Nd,Gd)3 phases in the microstructure of the T4 composites were the most uniform,and the interfacial stress transfer of the composites was not affected by the segregation of the needle-like Al_(11)(Nd,Gd)_(3)phase at the fiber,and the creep resistance at high temperature was the best.The maximum creep strain and steady-state creep rate were 0.5%and 6.94×10^(-9)s^(-1),respectively,which were reduced by 54.5%and 58.4%compared with the as-cast composites.