QUENCH-HARDENING EFFECTS ON VICKERS AND KNOOP MEASURES OF D-AHT CRYSTALS

Ammonium-hydrogen-d-tartrate (d-AHT) crystals are grown by slow chemic al reaction in silica gel. The quench hardness study of the crystals w as carried out on the cleavage plane (010) from room temperature (308 K) to 383 K. Their Knoop hardness and Vickers hardness have been compa red. For all applied loads and quenching temperatures, the Vickers har dness was found to be greater than the Knoop hardness. In the high loa d range (HLR), the hardness is found to be independent of the applied load. The average hardness, (H) over bar, in HLR is related to the que nching temperature, T-Q, through <(H)over bar T-Q(k)> = constant, wher e exponent k = -0.5.