Abstract
The paper is devoted to the study of structural characteristics of two types of functional biomaterial composed of plasma coated shape memory TiNi wires which are partly cast under vacuum into Ti6Al4V alloy. The α-Al₂O₃ plasma coating, approx. 130-180 µm thick, reacts with TiNi wire as well as with Ti6Al4V alloy in case of lower cooling rate. Under these conditions, the formed interphases are of Ti₄(Ni_xAl_y)₂(O,N)_z-type on the side of TiNi alloy and of Ti₃Al-type on the side of Ti6Al4V alloy. For higher cooling rate, these interphases are not found. Further, the optimum rolling conditions of studied composite material TiNi/Al₂O₃/Ti6Al4V are determined. The applied technique represents a reasonable compromise between the physical and metallurgical properties of coexisting constituents. The rolling temperature of 900 °C, and the reduction in one pass of 5% were recommended as optimum. The total deformation of the composite attained after the multipasses rolling is of 30%. The shear strength of TiNi plasma coated wires and Ti6Al4V alloy is higher than 100 MPa. In case of elimination of the transition phases formation (at higher cooling rate) at the interface of coexisting constituents, the shear strength of 60 MPa is found. The failure occurs dominantly in Al₂O₃ coating for a lower cooling rate and on TiNi/Al₂O₃ interface in specimens cooled at a higher rate.

Key words
structural characteristics, plasma coated shape memory TiNi wires, Ti6Al4V alloys, composite biomaterial

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