Thermodynamically guided composition design of in situ TiB ₂ ‐AlN ceramics with enhanced mechanical properties

Abstract Reactive sintering offers an advantageous route to produce high‐performance ceramics from coarse and cheap precursor powders; however, impurities in these sources often prevent the desired product composition from being achieved even when the raw materials are proportioned according to the reaction stoichiometry. This study employed a thermodynamics‐guided approach to predict phase evolutions during the consolidation of TiB 2 ‐AlN ceramics (TA) within the TiN–Al–B system. Although oxygen impurities (B 2 O 3 , Al 2 O 3 ) exist in the raw powders, the formation of undesirable phases in TA could be highly suppressed through a proper composition design. Thermodynamic calculations revealed that excess Al compensates for the reduction of B 2 O 3 , while a TiN deficiency below a critical threshold is essential to inhibit the formation of h BN. Guided by these insights, stoichiometric, Al‐excess (TA5: 5 mol% excess Al) and dual‐optimized (T5A5: 5 mol% excess Al and 5 mol% deficient TiN) were consolidated by spark plasma sintering at 1800°C/60 MPa for 5 min. Whereas TA and TA5 contained residual TiN and h BN, T5A5 achieved near‐phase purity with refined microstructures and exhibited better mechanical properties.