Profilometry-based Indentation Plastometry at High Temperature

This is a first report on Profilometry-based Indentation Plastometry (PIP) at high temperature, covering both thermal characterization and issues for obtaining stress-strain curves. The heating system has a relatively low thermal inertia, reaching 800˚C within about 10 minutes, while both indentation (~20 s) and cooling (~20 min.) are also quick. This capability is useful in terms of limiting exposure of the sample to prolonged periods at high temperature, and hence avoiding the formation of thick oxide layers (which could affect indent profiles and hence inferred stress-strain curves). There is good general consistency between stress-strain curves obtained via HT-PIP and those from tensile testing. However, the possibility of creep (time-dependent deformation) affecting the outcomes (of both types of test), particularly at higher temperatures, should be borne in mind. Creep has a characteristic effect on tensile curves, which can often be confirmed and investigated by changing the imposed strain rate. It can also be revealed by carrying out the HT-PIP testing with different penetration velocities or by monitoring the shape of the load-displacement plot.