CRYSTAL STRUCTURE AND PROPERTIES OF CHROMIUM WITH ADDITIONS OF V, Nb, Ta, La

L.O.Andrushchik, S.P. Oschkaderow, N.A. Storchak

Institute for Metal Physics 36, Vernadsky blvd UA-252680 Kiev 142, Ukraine

By using X-ray method was studied an influence of Vanadium, Niobium, Tantalum and Lanthanum on the period of the body centered cubic (b.c.c.) lattice a. It was carried out an investigation of microstresses E_m of the chromium alloys containing about 0,08 at.% interstitial atoms. The alloys were produced with sintering of pressed powder samples with direct passing of electric current in ones (electrical contact heating) and traditional metallurgy.

High accuracy X-ray technics used for investigation of influence of different thermotreatments on change of parameter a of b.c.c. grate. Distortions of structure (form and width B of reflections) were measured with resolution of angles D~ 0,001^o and the accuracy of determination of width and position of diffraction reflections D < 0,005^o. Results of the X-ray measurements were compared with data of optical and electron microscopy of investigated structures.

As were revealed the low of additivity of change of the parameter a from quality and quantity of the soluted elements are carried out in chromium alloys. Every alloy were determined had the termical range at which the parameter a was maximum. The change of width B of diffractional reflections (lines) correlated with one of dislocation structures and microhardness Hm. Chromium alloys with Vanadium formed solid solutions. There were observed the zonal (homogeneous or heterogeneous) structures having tendency to the grow old with changing properties of alloys. In function from containment of quantity and kind of alloyed elements it were observed displacement of maximum values of the parameter a of grate. The time of isothermal heating of the alloys promoted to proceeding of the structure and properties. In researched concentration fields the alloyed elements Vanadium (to 2,0 at.%), Niobium and Tantalum ( to 0,5 at.% each ones) formed the solid solution in the matrix b.c.c. lattice of Chromium. Forming of the solid solution with Niiobium and Tantalum atoms the matrix of Chromium strengthened ones (it was observed increasing microhardness H_m more than twice, in good accord with containing of these elements in alloys). An influence on H_m of Vanadium and Lanthanum is more complex as compared with mentioned earlier elements Nb and Ta. The technological peculiarities of the productions of alloyed Chromium determined the crystal structure of specimen dimensions, from distribution of the crystal faults. Changing of the period of b.c.c. lattice of chromium alloys is submitted to the additivity of the contributions of the alloyed elements (to Vegard low) and it was connected with structure of the formed crystals in the solid solutions.