High Strain Rate Behavior of Aluminum Produced by Powder Metallurgy

The presented study compares the compressive high strain rate behavior of Aluminum (Al) specimen fabricated from the powder as received, with the effect of ball milling and incorporation of high rock salt percent. Four different types of sample specimens were fabricated by compacting Aluminum powder followed by sintering in Argon atmosphere at 600 °C for 3 hours. Sample types comprised of (i) Aluminum powder as received, (ii) ball-milled Aluminum powder for 24 hours, (iii) Aluminum powder with 33% rock salt and (iv) specimen of type three boiled in a water bath, respectively. The compressive high strain rate testing was done on a 16 mm Titanium bars based Split Hopkinson Pressure Bar (SHPB). For identical incident energy, different strain rates and stresses were attained by these four different types of Al samples. Ball milling of Al powder for 24 hours resulted in significant property variation, which enhanced the peak stress under compressive high strain rate loading. However, the damage pattern shifted from ductile in case of non-milled powder to partly brittle damage for ball milled Al specimens. Incorporation of higher rock salt percent was meant to produce relatively low-density Al. The resulting compressive stresses recorded were much lower and the corresponding damage was brittle in nature. Boiling in water bath dissolved salt but could not enhance the properties of Al specimen. The study reveals the importance of Al powder processing on the rate dependent stress-strain behavior of Aluminum specimen fabricated by powder metallurgy route.