Study on strengthening mechanism of Ti/Cu electron beam welding

Abstract

Welding-brazing method is widely used for dissimilar metals welding. However, it is becoming increasingly difficult to further improve the connection strength by controlling the formation of the transition layer. In this study, an innovative welding method referred to as adjacent welding was addressed, which greatly improved the tensile strength of Ti/Cu dissimilar joint. The strength of new joint could reach up to 89% that of copper base metal, compared to the use of a traditional welding-brazing method which strength coefficient is within the limit of 70%. In order to determine the strengthening mechanism of adjacent welding, optical microscopy, SEM, EDS and XRD were applied for the analysis of microstructure and phase structure. Furthermore, tensile strength was also tested. The results show that due to the process of remelting and reverse solidification of intermetallic compounds (IMCs) layer, a less complex and thinner IMCs layer was formed and TiCu (553HV) with high embrittlement existing in the front of titanium substrate was changed into Ti2Cu (442HV). Performances of joints were optimized by these changes. An interpretation module was presented for the mechanism.

The Joining Behavior of Titanium and Q235 Steel Joined by Cold Metal Transfer Joining Technology

“…For joint II, although the micro-hardness value of interface reaction layer dispersed with TiFe 2 IMCs reached 800 HV (Figure 8a), the tensile force of Joint II exhibited a high value of 2.6 KN. It was attributed to the dispersed TiFe 2 IMCs strengthening the interface between the steel base metal and the Ti base metal [1]. Moreover, there was no distinct interface layer between the steel base metal and the weld metal, as shown in Figure 6b, and it was composed of (Cu) and Al 3 Ti, and Fe-Al-Cu IMCs.…”

“…Titanium and titanium alloy, with their excellent corrosion resistance and high specific strength compared to steel, are widely applied in chemical and aerospace industries [1,2,3,4]. Zn coated steel is used due to their good corrosion resistance.…”

“…However, it is difficult to successfully join titanium and steel directly based on the following two aspects: On the one hand, brittle intermetalics (IMCs) (TiFe and TiFe 2 ) are formed due to low solubility of Fe in Ti (0.1 at. %, at room temperature) [1]. On the other hand, a significant mismatch of thermal expansion coefficients between these two materials results in large residual stress especially in the case of arc welding process with large heat input [9].…”

Effect of temperature on morphology and wear of a Cu-Ti-TiC MMC sintered by abnormal glow discharge

“…At temperatures above 805°C had been observed the allotropic transformation up to 905°C [35,36]. In addition, the high difference between the thermal conductivity of titanium and copper [37] (Ti: 15.7 W.K −1 .m −1 , Cu: 393.6 W.K −1 .m −1 ) produced the formation of heat concentrations inside the titanium grains by a lower heat dissipation. As a result, this concentration of energy in reason of the Joule effect and cathodic emission of the discharge due to predominantly metallic particles promote in the external zone of the titanium particle in contact with the matrix a greater possibility of dissipating the heat through the interface with the copper, which promoted a strong interaction with the matrix (Cu-TiC).…”

“…The results at 850°C shown the presence of a rich phase Cu 3 Ti accompanied by CuTi 2 , CuTi, Cu 4 Ti 3 in minority. These phases produced a MMC with moderately ductile precipitates within the intermetallic group of the Cu-Ti system with an average hardness of 544.34 HV for Cu 3 Ti [39], which together with the intermetallic CuTi 2 , CuTi (533 HV) [37], and Cu 4 Ti 3 (587.15 HV) provided high hardness values. At 20%, a microhardness of 457.62 HV was presented as the highest value compared to the other study conditions.…”