PSI - Issue 14

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Tulsi Chouhan et al. / Procedia Structural Integrity 14 (2019) 883–890 Author name / Structural Integrity Procedia 00 (2018) 000–000

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Though lower peak stresses were recorded for this set of the specimen, nonetheless constant stress growth of strain may be noted in Fig. 2 (d). Both the salt containing and salt dissolved Al specimen underwent brittle damage; the resulting stresses were also lower. The lowest strain growth is associated with salt dissolved Al specimen. Incorporation of rock salt followed by sintering resulted in weak interfaces in between the Aluminum powder particles. Salt restricted sintering in between the Aluminum particles and owing to its high melting temperature (above 1400  C) the salt could not be sintered as well. Presence of salt however, enhanced the heat induced softening which resulted in gradual stress fall. Boiling in water bath partly removed the salt from the sintered Aluminum specimens. However, the resulting specimens were void filled. Void formation served as a site for the easy deformation of loosely sintered matrix. Therefore, further lower stresses were expected and proven experimentally. Similar stress reduction as a function of void/foam is already proven in the literature (Peroni, Solomos, and Pizzinato 2012). Comparison of strain, stress and toughness with the increasing strain rate of loading is presented in Fig. 3. An identical slope of strain growth for all the material system is depicted with salt-containing specimen leading the curve (Fig. 3(a)). On comparison of stresses, it is observed that 24 hours of ball milling of Al powder resulted in the best possible specimen, followed by Al as received specimen. The worst properties are noted for the Al specimen boiled in a water bath. The relatively better performance was recorded for salt containing Al specimen (Fig. 3 (b)). Similar to stress, toughness-strain rate curve also revealed the best performance of ball milled Al specimen, followed by as received Al and salt containing Al specimen. Toughness being derived from the area under the stress-strain curve was noted least for specimen kept in the boiling water (Fig. 3 (c)).

0.3

Milled 24 hours Al with 33% rock salt

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Milled 24 hours Boiled in water

Al with 33% rock salt

Al as received

Boiled in water Al as received

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Strain

0.15

Stress (MPa)

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0.1

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Strain rate (/s)