研究经近等温变形的Ti_3Al/TC11双合金在梯度热处理前后,焊接界面显微组织和显微硬度的变化.结果表明,Ti_3Al侧热影响区的显微组织在梯度热处理前后变化较小是因为晶界α_2相较稳定;焊缝区显微组织变化较大,究其原因是近等温变形造成的晶粒破碎和Ti、Al、Nb等原子的扩散,造成α、α_2相互制衡,致使不能形成连续晶界α_2或晶界α;TC11合金基体经过梯度热处理后从网篮组织转变成等轴组织;显微硬度的提高是因为Ti、Al、Nb扩散,造成α、α_2尺寸小、弥散分布所致.
The changes of the microstructure and the microhardness at the weld interface of near isothermally forged Ti_3Al/TC11 dual alloys before and after gradient heat treatment were investigated. The results indicate that the stability of α_2 phase and distribution in the grain boundary results in slight changes of microstructures at heat-affected zone on Ti_3Al side, but the changes of the microstructure in the weld zone are relatively obvious due to the diffusions of elements such as Ti, Al, Nb and so on. Because growing-up of the α and α_2 phase is restricted each other, the continual α or α_2 phase grain boundary can not be formed. After gradient heat treatment, the matrix microstructure of the TC11 alloy changes from basketweave structure to equiaxed structure. Because of the diffusions of Ti, Al and Nb, the sizes of α and α_2 phases become small and their distribution become dispersive, resulting in the increase in microhardness.
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