Abstract: The electron beam welding was made on 2 mm-thick Qcr0.8 and 1Cr21Ni5Ti. The microstructural characteristics and compositions were investigated by optical microscope and scanning electron microscope. The actual microstructural characteristics were identified. According to the characteristics of the electron beam welding, a physical model was built about electron beam welding joint formation mechanism on the equal thick Qcr0.8 and 1Cr21Ni5Ti. The formation mechanism of unhomogeneous joint structure was discussed. The results show that microstructure of QCr0.8/1Cr21Ni5Ti joint consists of Cu(Fe)＋(α+ε) casting mixed structures, which are very unhomogeneous in microstructure and chemical composition. The macrostructure can be divided into three parts. There are alike microstructure zones at the bottom of the joint and top near QCr0.8, which consist of Cu(Fe) dispersed of some discrete unhomogeneous α+ε. There is α+ε zone with little discrete Cu(Fe) at the middle of the joint. The joint microstructure is formed through five phases: the metal melting and keyhole forming phase, the initial solidifing phase(γ＋ε) is separated out and three zones are shaped in this phase), the medial solidifing phase(γ＋ε crystallization), the upper solidifing phase(Cu(Fe) is formed and joint is solidified) and the terminative solidifing phase(elements diffusing, γ→α phase transformation， final microstructure formed).
Microstructures and formation of electron beam welding joint of QCr0.8 and 1Cr21Ni5Ti
Abstract：
The electron beam welding was made on 2 mm-thick Qcr0.8 and 1Cr21Ni5Ti. The microstructural characteristics and compositions were investigated by optical microscope and scanning electron microscope. The actual microstructural characteristics were identified. According to the characteristics of the electron beam welding, a physical model was built about electron beam welding joint formation mechanism on the equal thick Qcr0.8 and 1Cr21Ni5Ti. The formation mechanism of unhomogeneous joint structure was discussed. The results show that microstructure of QCr0.8/1Cr21Ni5Ti joint consists of Cu(Fe)＋(α+ε) casting mixed structures, which are very unhomogeneous in microstructure and chemical composition. The macrostructure can be pided into three parts. There are alike microstructure zones at the bottom of the joint and top near QCr0.8, which consist of Cu(Fe) dispersed of some discrete unhomogeneous α+ε. There is α+ε zone with little discrete Cu(Fe) at the middle of the joint. The joint microstructure is formed through five phases: the metal melting and keyhole forming phase, the initial solidifing phase(γ＋ε is separated out and three zones are shaped in this phase), the medial solidifing phase(γ＋ε crystallization), the upper solidifing phase(Cu(Fe) is formed and joint is solidified) and the terminative solidifing phase(elements diffusing, γ→α phase transformation, final microstructure formed).
