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Alloys ZhS6U-VI and ZhS3DK-VI modified jointly and individually with zirconium {0.05"i,) and hafnium (0.5%) arc described. It is established that complex modifying increases the strength and ductility properties of the alloys. The microhardness of alloy ZhS6U-VI is increased after tests for long-term strength. In alloy ZhS6U-VI tested for long-term strength cy-phase segregates in the form of flake and acicular particles. Modification of the alloy with hafnium increases the content of the flake o-phase, modification with zirconium increases the content of the acicular G-phase.

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The present work is devoted to the effect of modification of high-temperature alloys ZhS6U-VI and ZhS3DK-VI with hafnium on their properties and structure. Alloys ZhS6U-VI and ZhS3DK-VI were molten in a vacuum induction furnace and modified with hafnium in an amount of 0 -1.5% (as calculated) using a nickel-hafnium alloying composition. It is shown that hafnium alloying diminishes the sizes and amount of the brittle component in a fracture and the distance between the second-order dendrite axes and changes the morphology of the carbides. With growth of the hafnium content the mechanical properties of both alloys and the high-temperature strength of alloy ZhS3DK-VI at room temperature increase.The alloys were melted by the method of remelting a measured preform in a UPPF-3M vacuum induction furnace in a crucible with a basic lining and a capacity of 7.5 kg. A weighed portion of a hafnium-nickel alloying composition of fraction i-3 mm was introduced into the melt heated to 1600~ 1.5 min before discharging. The composition provided the introduction of 0, 0.5, and 1.5% Hf 2 (as calculated) into alloy ZhS6U-VI and 0, 0.8, 1.0, and 1.2% Hf into alloy ZhS3DK-VI. Blocks of finger specimens were fabricated by the method of precise casting by melted models (the casting temperature was 1560 -1580~We determined the chemical composition of the alloys with modification by the mentioned variants and studied the macro-and microstructure before and after heat treatment (homogenizing at 1210~ for 4 h, cooling in air) and the i Motor-Sich Joint-Stock Company, Ukraine; Zaporozhe State Engineering University, Zaporozhe, Ukraine. 2 Here add below in the paper the content of elements is given in mass fro ctions.morphology of the main hardening intermetallic "/'-phase under a 10,000-fold magnification on a JSMT-300 scanning electron microscope. The ultimate rupture strength err, the specific elongation 8, and the impact toughness KCU were determined at room temperature. Tests for long-term strength were conducted on a DST-5000 installation. We determined the time before fracture of specimens of alloy ZhS6U-VI during a hold at t = 760~ o = 590 MPa and t = 975~ o = 230 MPa and that of alloy ZhS3DK-VI at t = 850~ and o = 350 MPa. The chemical composition of alloys ZhS6U-VI and ZhS3DK-VI (Table 1) met the requirements of the OST 1.90.126-85 standard. Hafnium was assimilated in the given alloys in an amount of 55%.Results of a fractographic analysis of heat-treated and fractured impact specimens of alloy ZhS3DK-V1 are presented in Fig. la-d, and ones for alloy ZhS6U-VI are presented in Fig. le-g. It can be seen that in fractures of alloy ZhS6U-VI without hafnium additives the brittle component TABLE 1