STRAIN RATE DEPENDENCE ON THE HIGH TEMPERATURE MECHANICAL BEHAVIOR OF THE NI-18SI-3.0NB-1.0CR-0.2B INTERMETALLIC ALLOY
Abstract
The effect of strain rate and temperature on the mechanical behavior of the Ni-18Si-3.0Nb-1.0Cr-0.2B alloy was investigated by atmosphere-controlled tensile testing in vacuum and air atmosphere at different strain rates and different temperatures. The results reveal that the Ni-18Si-3.0Nb-1.0Cr-0.2B alloy exhibits ductile mechanical behavior (UTS > 1200 MPa, ε > 8%) at room temperature under different atmosphere conditions. In addition, both of the ultimate tensile strength and elongation exhibit quite insensitive response with respect to the loading strain rate when tests are held at temperatures below 973K. The elongation of the samples tested in vacuum and air for the Ni-18Si-3Nb-1Cr-0.2B alloy exhibits a significantly increase with temperature from 973K to 1073K. In addition, all fracture surfaces tested at 1073K in vacuum and air atmosphere presents a typical ductile fracture surface, a fully dimpled fracture pattern. The fact of increasing in elongation at high temperature (1073K) is suggested to be attributed by the dynamic recrystallization that occurs preferentially around the dispersion phase or grain boundaries and so as to enhance the ductility by reducing the stress concentration at or near grain boundaries.
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