Mechanical properties and microstructural characteristics of laser and electron-beam welds in V-4Cr-4Ti

[摘要] Mechanical properties and microstructural characteristics of laser and electron-beam (EB) welds of a 500-kg heat of V-4Cr-4Ti were investigated in as-welded condition and after postwelding heat treatment (PWHT) by impact testing, microhardness measurement, optical microscopy, X-ray diffraction, and transmission electron microscopy (TEM). Ductile-brittle-transition temperatures (DBTTs) of the laser and electron-beam welds were significantly higher than that of the base metal. However, excellent impact properties could be restored in both types of welds by postwelding annealing at 1000 degrees C for 1 h in vacuum. Analysis by TEM revealed that annealed weld zones were characterized by extensive networks of fine V(C,O,N) precipitates, which clean away O, C, and N interstitials from the grain matrices. This process is accompanied by simultaneous annealing-out of the dense dislocations present in the weld zone. This finding could be useful in identifying an optimal welding procedure by controlling and adjusting the cooling rate of the weld zone by an innovative method to maximize the precipitation of V(C,O,N). (C) 1998 Published by Elsevier Science B.V. All rights reserved.

[发布日期] 1998-10-01

[效力级别]  Proceedings Paper