The effect of density anisotropy on the yielding and flow behavior of partially consolidated powder compacts

The effect of density anisotropy on the flow behavior of partially consolidated powder compacts of an alpha-two titanium aluminide alloy (Ti-24Al-11Nb) was established by conducting hot compression tests on samples made by hot die pressing or hot isostatic pressing ("hipping"). For the former consolidation method, in which anisotropic density distributions were developed, the upset tests were conducted both parallel and perpendicular to the die pressing direction. The flow stress results from these experiments, as well as those from the tests on the "hipped" material, were interpreted in terms of calculations of the stress intensification factor (phi). When the stress intensification factors were plotted as a function of areal relative density, rather than volumetric relative density, a unique dependence of phi on density was obtained. This dependence showed a smooth transition from a behavior measured by others for the early stages of densification to a behavior theoretically predicted for the latter stages of densification, in which isolated pores are closed.