(清華大學(xué) 機(jī)械工程系 教育部先進(jìn)成形制造重點(diǎn)實(shí)驗(yàn)室，北京 100084)
摘 要: 研究Ti-24Al-17Nb合金激光焊接接頭的室溫及高溫拉伸性能，并分析接頭顯微組織和拉伸斷口。研究結(jié)果表明，室溫下焊縫為單一β/B2相柱狀晶組織，室溫橫向拉伸時(shí)接頭強(qiáng)度與母材強(qiáng)度相當(dāng)、塑性有所下降、但仍有25%左右的伸長(zhǎng)率，斷裂大部分發(fā)生在母材部位、少部分?jǐn)嗔言诤缚p；高溫拉伸時(shí)斷裂均發(fā)生在焊縫部位。高溫拉伸時(shí)，接頭組織發(fā)生變化，α2相和B2相向O相轉(zhuǎn)變；焊縫β/B2相向O相轉(zhuǎn)變的切變相變，使原來柱狀晶晶界應(yīng)變集中、容易產(chǎn)生微裂紋，使接頭高溫強(qiáng)度和塑性明顯降低，高溫拉伸斷口呈現(xiàn)沿晶斷裂和解理斷裂的脆性斷裂形式。
關(guān)鍵字: Ti3Al合金；激光焊接；高溫拉伸性能；顯微組織
（Key Laboratory for Advanced Materials Processing Technology; Ministry of Education;Department of Mechanical Engineering; Tsinghua University; Beijing 100084, China）
Abstract:Abstract: The high-temperature and room-temperature tensile properties of Ti-24Al-17Nb (mole fraction, %) alloys laser welding joints were investigated, and the microstructure and fracture of the joints were studied. The results indicate that the microstructures of the welds are consisted of β/B2 with columnar crystals, the strength of the joints tensioned transversely at room-temperature is almost same as that of the base metal, and the ductility reaches 25%. Cracks occur in the base metal. During the high-temperature tension the cracks occur in the welds. After high-temperature tension, some of the phase α2 and phase B2 of the base metal and HAZ in joints turn to phase O, and phase B2 of the welds turn to phase O. The phase changes bring about strain concentration, and induce fracture. The strength and ductility of the joints at high temperature descend significantly. The fracture types of high-temperature tension joints are intergranular fracture and cleavage fracture.
Key words: Ti3Al alloy; laser welding; high-temperature tensile property; joint microstructure
