V5Cr5Ti与HR-2电子束熔焊接头微观结构与力学性能研究

采用OM、XRD、TEM等分析手段和力学测试方法,研究了钒合金(V5Cr5Ti)与HR-2电子束焊接接头的微观结构与力学性能。研究表明：电子束焦点偏移结合斜I型对接坡口,控制焊缝V5Cr5Ti体积熔合比小于15%可实现V5Cr5Ti与HR-2异种材料无缺陷熔焊连接,接头抗拉强度约400Mpa,断口呈现典型的混合型特征。V5Cr5Ti/HR-2接头焊缝边缘相结构取决于其区域V原子的富集程度,富集程度低,生成Fe-Cr体心立方固溶体,V原子以置换晶格中Fe原子形式存在；富集程度高,则形成Fe_0.1Ti_0.18V_0.72、V₂Cr₂Fe金属间化合物。焊缝中心区域相结构与熔合比无关,皆生成Fe-Cr体心立方固溶体；V5Cr5Ti/HR-2焊缝热、冷裂纹影响因素一是因焊缝生成富钒金属间化合物,二是接头在整个焊接热循环期间将承受较大焊接热应力及其随后的残余应力。

Research on the microstructure and mechanical property of electronic beam melt welded joint for V5Cr5Ti and HR-2 steel

In this study, the welding joint of vanandium alloy (V5Cr5Ti) and HR-2 steel was investigated based on the microstructural analysis and mechanical property by optical microscope (OM),X-ray diffraction(XRD),transmission electron microscope(TEM).Results show that using both focus point migration and inclided groove, a defect-free joint can be achieved when the fusion ratio of vanandium alloy was controlled to be less than 15%. The tensile strength is approximately 400 MPa, and the fracture surface exhibits typical mixed fracture mode. The formation of phases in the weld boundaries is affected by the fusion ratio of vanadium alloy and the directional diffusion of vanandium atoms to the low temperature zone during initial stage of solidification. When the degree of vanandium enrichment is low, Fe-Cr substitutional solid solution with bcc structure is formed. When the V/Fe ratio was higher than 4 ot 2, intermetallics such as Fe_0.1Ti_0.18V_0.72, V₂Cr₂Fe appear. The occurrence of hot cracking and cold cracking is due to the formation of vanadium-rich intermetallics, thermal stress (approximately 400 MPa) during welding cycle and residual stress (approximately 300 MPa).