NB-AL2O3 AND CR-AL2O3 COMPOSITES WITH INTERPENETRATING NETWORKS

Cr-Al2O3 and Nb-Al2O3 composites containing 50 vol% metal have been fa bricated by pressureless sintering of compacts of attrition milled pow der mixtures. Successful fabrication of high-strength and high toughne ss composites requires fine and homogeneous powders. Strength and frac ture roughness of the composites increase with increasing milling time . Short milling times do not lead to the required particle fineness an d powder homogeneity. For a composite containing 50 vol% Nb, strengths of up to 690 MPa with corresponding fracture toughness of 6.6 +/- 0.4 MPa m(1/2) and hardness of 11.2 GPa (H-V20) have been obtained, where as strengths of 592 MPa, fracture roughness of 6.6 +/- 0.3 MPa m(1/2) and hardness of 9.3 GPa have been obtained for Cr-Al2O3 composites. (C ) 1998 Elsevier Science Limited. All rights reserved.