A fracture locus for a 10 volume-percent V95 / SiC metal matrix composite at the near-solidus temperature

Abstract

A fracture locus for a 10 vol% V95 / SiC metal matrix composite at near-solidus temperature is obtained from experiments. The fracture locus determines a functional dependence of the value of ultimate metal ductility on the stress state characteristics. To study ultimate metal ductility, test specimens are deformed under prevailing compressive stresses. Tests for cylindrical specimen compression, bell-shaped specimen compression, cylindrical specimen torsion and for supported extrusion of the bottoms of thick-walled thin-bottomed cups are used. The tests are simulated by the finite element method to evaluate the stress-strain state in the fracture region. An isotropic elastic-plastic strain-hardening model is used as the material to be deformed. The forming tools are considered rigid. The strain state is viewed as axisymmetric; therefore, only a half of the longitudinal section of the specimen is simulated. The fracture locus makes it possible to evaluate the ultimate ductility of the composite as a function of the stress triaxiality factor k and the Lode-Nadai coefficient μ σ. The stress triaxiality factor characterizes the relative level of normal stresses. The Lode-Nadai coefficient characterizes the form of the stress state. The combination of these parameters uniquely characterizes the stress state under plastic deformation. The fracture locus can be used in the ranges-1.2 < k < 0.4 and 0 < μ σ < +1. The obtained fracture locus is applicable to the evaluation of the damage accumulated in workpieces for machine parts and structural components made of this composite. Thus a workpiece production process can be optimized.