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Zirconium diboride (ZrB2) is a credible candidate for hypersonic aerospace applications owing to magnificent characteristics such as higher melting point temperature, higher hardness, higher thermal conductivity, moderate oxidation, and ablation resistance. The influence of MgO (1–3 vol%) on mechanical and ablation characteristics of ZrB2–SiC composites sintered via microwave sintering was investigated in the present study. The microwave sintering was performed at 1800 °C under the heating rate of 15 °C/minute and holding time of 40 min at maximum temperature. The MgO addition not only reduced the sintering temperature but also enhanced the fracture toughness of developed composites. The maximum relative density and microhardness were observed at 2 vol% MgO. The maximum fracture toughness was achieved at 3 vol% MgO. The prominent toughening mechanisms (crack bridging, crack deflection, and particle pull out) enhanced the fracture toughness. The ablation resistance was improved with the addition of MgO and composites containing 2 vol% MgO exhibited the highest ablation resistance. The developed composites have applications in the rocket nozzles, nose caps, and leading edges of aerospace hypersonic carriers. [ABSTRACT FROM AUTHOR]

In this work, a hybrid pattern material is introduced for investment casting process to enhance the properties/characteristics of the pattern. The hybrid pattern material is prepared by mixing coconut oil into conventional wax pattern material's ingredients and named as coconut oil-based hybrid (COBH) pattern material. A comprehensive experimentation was performed to examine the influence of injection parameters viz. injection temperature (IT), injection flow rate (IFR), and die temperature (DT) on COBH pattern characteristics such as surface roughness (SR), average shrinkage (AS), and needle penetration (NP). Regression models were developed and statistically analyzed. Additionally, multi-response optimization (MRO) was carried out using the desirability technique for minimum SR, AS, and NP. The ANOVA results revealed that all input variables significantly influenced the characteristics of the COBH pattern. The optimal parametric settings of IT = 65°C, IFR = 3.5 lpm and DT = 35°C obtained by MRO provided the desired responses (i.e., minimum SR, AS, and NP). The developed COBH pattern ban be utilized for the development of good quality castings. [ABSTRACT FROM AUTHOR]