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Chapter VIII Micro-hardness studies…
values increased for different additive values [43]. According to Patel and
Arora [44], Vickers hardness increases as load increases for strontium tartrate
crystals. Apart from this, the variation of Knoop hardness with load and the
orientation of strontium tartrate crystals was studied by Joseph [45]. However,
there are recent studies on the temperature and dwell time effect on hardness
[46] and hardness variation across bulk metallic glass [47].
Almost three decades back the micro-hardness studies on KDP
crystals were reported by Kishan Rao and Sirdeshmukh [48], Joshi and
Antony [49] as well as by Joshi et al [50] and Anbukumar et al [51]. Kishan
Rao and Sirdeshmukh [48] have found two different values of hardness for
normal to (100) and (001) planes, which are 1.43 GPa and 1.29 GPa,
respectively. Joshi and Antony [49] as well as Joshi et al [50] have studied
dependence of hardness on indentation load and anisotropy of (100) and
(011) planes of KDP crystals. They also indicated the presence of crack
patterns around the indentation mark; which were found to be dependent on
the indenter orientation [50]. Anbukumar et al [51] have measured Vickers
micro-hardness on (100) planes of KDP within the load range from 5 to 50 g
and found the variation of hardness from 1.77 to1.57 GPa. They have also
observed that the indentation increased with increase in applied load.
Micro-hardness studies on (100) face of gel growth KDP and ADP
crystals are reported by Sengupta and Sengupta [52]. They observed slip
lines on the (100) face of ADP crystal at corners of the impression mark.
However, the micro-crack were observed around the indentation on (100) face
of KDP crystals from 10 g load, which spread out as the load increased. The
Vickers micro-hardness decreased as applied load increased for both crystals
and the work hardening coefficient was less than 2, which indicated the soft
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