Microstructure and mechanical properties of Al₂O₃/TiAl joints brazed with B powders reinforced Ag-Cu-Ti based composite fillers

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• 作者：G.B. Niu ^{niuwelding@tju.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; D.P. Wang ^{wangdp@tju.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Z.W. Yang ; ^{tjuyangzhenwen@163.com" class="auth_mail" title="E-mail the corresponding author} ; ^{yangzw@tju.edu.cn" class="auth_mail" title="E-mail the corresponding author} ; Y. Wang ^{wangycl@tju.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：B. whisker ; D. Al2O3 ; TiAl alloy ; Brazing
• 刊名：Ceramics International
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：43
• 期：1
• 页码：439-450
• 全文大小：3400 K

文摘

In this manuscript, Al₂O₃ ceramic and TiAl alloy were brazed with Ag-Cu-Ti based composite fillers containing B powder additive. The effects of B content, Ti content, and the brazing temperature on the microstructure and mechanical properties of the brazed joints were investigated. The typical interfacial microstructure of the brazed joint was: Al₂O₃/Ti₃(Cu, Al)₃O/Ag(s.s)+TiB+Ti(Cu, Al)+fine AlCu₂Ti/blocky AlCu₂Ti+AlCuTi/TiAl. TiB whiskers synthesized in situ by the reaction of the B additive with Ti, served as nucleation sites for the formation of fine Ti(Cu, Al) and AlCu₂Ti grains and improved the bonding properties. With increasing B content, more fine-grains were formed in the brazing seam and the thickness of the Ti₃(Cu, Al)₃O reaction layer adjacent to the Al₂O₃ ceramic decreased. Brazing parameters also influenced the joint microstructure. Growth of Ti₃(Cu, Al)₃O layer and AlCu₂Ti formed with increase in brazing temperature. Moreover, the formation of dispersed fine-grains in the brazing seam depended largely on the initial Ti content in the composite filler. With increase in initial Ti content, the TiB-reinforced area was broadened while the blocky AlCu₂Ti content decreased gradually. The maximum shear strength of Al₂O₃/TiAl joint brazed with B-reinforced composite filler was 148 MPa, which was 246% higher than that brazed without B addition. The joint shear strength was determined by the combined influences of the thermal expansion mismatch between the joined materials, the thickness of the Ti₃(Cu, Al)₃O layer, and the presence of defects in the joints.