The Ring Test for P/M Materials

Abstract

The application of the ring test to assess die-workpiece interface friction during forging of powder metallurgical materials has been investigated. As for fully dense materials, the change in internal diameter as a function of height reduction was used to quantify friction. To this end, calibration curves were generated by conducting finite element method (FEM) simulations of ring forging with different friction factors. The method was validated by conducting isothermal, hot compression tests on rings of an alpha-two titanium aluminide alloy with starting densities of 75, 85, or 100 percent of full theoretical density. Comparison of the test data to the calibration curves revealed somewhat higher friction factors for the porous materials (as compared to the fully dense material) for both lubricated and unlubricated interface conditions. Furthermore, the accuracy of the FEM simulations of the ring test was confirmed by good agreement between measured and predicted density distributions and load-stroke curves for tests on the porous titanium aluminide material.