Prediction and Confirmation of Phases Formed in the Diffusion Zone of Ti-5Ta-2Nb/304L SS Explosive Clads

Abstract

Explosive cladding, a solid-state welding technique was used to fabricate dissimilar joints between Ti-5Ta-2Nb alloy and 304L austenitic stainless steel. To remove the residual stresses and improve the ductility of the 'as clad' joints, further heat treatments were carried out in the temperature range of 873 K to 1073 K (600°C to 800°C) for varying durations. Systematic change in the interface microstructure and microchemistry due to thermally activated interdiffusion of alloying elements was studied. This information together with that of the thermal stability of non-equilibrium phases in base materials was used to evaluate the probability of formation of various phases across the explosive clad interface using JMatPro Ò , a materials modeling software. In the clad heat treated at 1073 K (800°C) for 20 hours, evidence was obtained for the presence of different phases (predicted to form) in the diffusion zone by transmission electron microscopy on site-specific specimens prepared by focused ion beam milling. An attempt to understand the specific influence of the type of phase, their relative mole fraction, and microchemistry on the mechanical property of the joint has also been made based on both experimental and computational study.

Effect of alloying elements on interdiffusion phenomena in explosive clads of 304LSS/Ti–5Ta–2Nb alloy

“…9b. Analysis of the SAD pattern confirms the presence of cubic-FeTi (a = 0.316 nm) and hcp-Fe 2 Ti (a = 0.47 nm, c = 0.78 nm) phases along [ 111] and [2 1 10] zone axis, respectively [4].…”

“…This method is used in the present study to determine the concentration-dependent interdiffusivities of Fe-Ti system (ignoring the effect of other diffusing elements) at temperatures of 550 and 600°C, since nature of the profiles resembles error function profiles. Considerable redistribution of the alloying elements at temperatures C700°C, suggests formation of intermetallic and secondary phases at the interface [4]. Therefore, the well-known Wagner's method (Eq.…”

“…Earlier, in the author's laboratory, explosive cladding process was employed to join 304L austenitic stainless steel (SS) and Ti-5 wt%Ta-2 wt%Nb (TiTaNb), an a?b alloy for an important industrial application in the spent nuclear fuel reprocessing plant [3]. Subsequent diffusion annealing of the clads at temperatures in the range of 550-800°C for various durations resulted in the formation of various reaction zones at the interface due to interdiffusion of the alloying elements [4]. Objective of the present study is to understand the growth characteristics of these diffusion zones in terms of temperature and concentration-dependent interdiffusion parameters using Secondary and Back Scattered Electron (SE/BSE) imaging as well as Electron Probe Micro Analysis (EPMA).…”

“…Although both BM and DB methods yielded identical results in Cu-Ni and Ta-W [10] systems, the latter is widely used due to its mathematical ease [11,12]. Based on our earlier investigations on heat-treated SS/TiTaNb explosive clads, an appreciable variation in molar volume with concentration is expected at temperatures beyond 700°C [4]. Sangeeta and Aloke Paul in a recent publication [13] have laid emphasis on incorporating the effect of molar volume for accurate determination of intrinsic diffusion coefficients in V 3 Ga system and have proposed the use of Wagner's method [14], when substantial molar volume change is involved during interdiffusion.…”

Interface Characteristic of Explosive-Welded and Hot-Rolled TA1/X65 Bimetallic Plate

“…Bimetallic sheets in which TA1 is used as the material of the flyer plate instead of steel can greatly improve the life of the refining equipment and pipeline. In recent years, researchers have conducted many studies on the microstructure and mechanical properties [26][27][28][29][30][31][32][33][34][35], heat treatment [36][37][38], hot rolling process [39], residual stress [40], bonding mechanism [41][42][43] and butt welding process [44,45] of explosive bonded Ti/Steel bimetallic sheets. These work mainly focused on the bimetallic sheet itself, while investigation regarding the suitability of explosive bonded Ti/Steel bimetallic sheet for the subsequent process, such as the JCOE process (progressive forming process of 'J' forming, 'C' forming and 'O' forming, reducing gap, welding and mechanical expanding), was rather limited.…”