Properties of AlMgB14 hot pressed with additions of ZrB2 and HfB2

• Published in: Powder technology 2013-02, Vol.235, p.968-974
• Main Authors: Gaballa, Osama, Ball, Jonathon H., Cook, Bruce, Peters, J.S., Russell, Alan
• Format: Article
• Language: English
• Subjects: Aluminum magnesium boride; aluminum oxide; Applied sciences; Chemical engineering; Constituents; Erosion mechanisms; Erosion rate; Exact sciences and technology; Fracturing; Hafnium diboride; Hard materials; hardness; High resistance; Hot press; Impurities; microstructure; milling; Miscellaneous; powders; scanning electron microscopy; Solid-solid systems; temperature; Wear; Wear resistance; X-ray diffraction; Zirconium diboride
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2012.12.015

Powders of AlMgB14, ZrB2, and HfB2 were combined by high-energy milling to produce AlMgB14+60vol.% ZrB2 and AlMgB14+60vol.% HfB2 composites. The powder constituents were hot pressed at two different temperatures, depending on prior conditioning of the milling vials. SEM and EDS were used to analyze microstructure impurities, and fracture mechanisms. XRD was used to verify proper phase formation and to check for impurity phases. The bulk AlMgB14+ZrB2 and AlMgB14+HfB2 show up to 97.3% and 98% densification, 22.2 and 24.5GPa hardness (measured at 5K-gf), and 4.1 and 3.7MPa(m)1/2 toughness, respectively. Also the study of bulk AlMgB14+ZrB2 and AlMgB14+HfB2 composites has shown that these materials exhibit high resistance to erosive and abrasive wear. Multi-hour ASTM erosion tests with Al2O3 abrasive material against composite samples comprised of AlMgB14 (40vol.%)+ZrB2 (60vol.%) and AlMgB14 (40vol.%)+HfB2 (60vol.%) resulted in erosion rates as low as 4.49mm3 of (AlMgB14+ZrB2) wear per kg of erodent and 2.85mm3 of (AlMgB14+HfB2) wear per kg of erodent. These values were compared with 14.9mm3/kg for wear-resistant grades of WC–6%Co. Multi-hour ASTM erosion tests for samples comprising AlMgB14+ZrB2 (60vol.%) and AlMgB14+HfB2 (60vol.%) resulted in erosion rates as low as 4.49 and 2.85mm3 of (AlMgB14+ZrB2) and (AlMgB14+HfB2 ) wear per kg of erodent respectively. These values were compared with 14.9mm3/kg for wear-resistant grades of WC‐6%Co. [Display omitted] ► AlMgB14+ZrB2 or HfB2 shows 97% and 98% densification, 22 and 24.5GPa hardness. ► Erosion rates of samples are 4.5 and 2.85mm3/kg, compared to 10.5mm3/kg WC–6%Co. ► AlMgB14+HfB2 were harder and more erosion-resistant than those with ZrB2. ► AlMgB14+ZrB2 or HfB2 results fall between the grade K68 and Roctec 500 WC grade.