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[References: 22 tit.]

The structural-phase state of the heat-affected zone of a weld produced by modulated current (fine-droplet transfer) on 0.12 C-18Cr-10Ni-1Ti-Fe austenitic steel was studied by transmission diffraction electron microscopy method on thin foils. Welding modes: amperage and pulse time - 75 А, 0.15 sec., amperage and pause time - 15 А, 0.45 sec, average while-welding amperage - 42 A. The studies were carried out in a heat-affected zone at a 1 mm distance from the fusion line in the base metal's direction - base metal's zone; and the one at a distance of 0.5 mm in the deposited metal's direction - the deposited metal's zone. It was discovered that before welding the steel matrix is a [gamma]- phase (austenite) having a face-centered cubic crystal lattice. Morphologically the steel structure is represented by the grains, a defective structure of which is only formed by a grid dislocation substructure, and the grains which host mechanical (or deformation) micro-twins in the form of packages of one, two or three systems along with the dislocation substructure. Micro-twins possess a crystal lattice and such parameter as [gamma]-phase. The micro-twins' allocation occurs along the {111} [gamma]-phase planes. It was found out that welding in the base metal's zone leads to [epsilon]-martensite formation both in the base (welded) and in the deposited (weld) metals. Moreover, [gamma]->[epsilon] phase transformation in the weld metal's zone is more intense and takes place in all [gamma]-phase grains.