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In this work, the creep behaviour of β-Sn single crystals having different growth directions under different peak indentation test loads (10, 20, 30, 40, and 50 mN) was investigated at room temperature during indentation tests. It was found that a ‘nose’ appears in the unloading segment of the applied indentation test load–penetration depth curve. When a ‘nose’ occurs, the apparent unloading stiffness Su, defined as dP/dh, is negative and the reduced modulus can no longer be calculated from the Oliver–Pharr method (Oliver and Pharr 1992 J. Mater. Res. 7 1564). The ‘nose’ disappears when the load hold before unload is lengthened. The correction term due to the creep is the ratio of indenter displacement rate at the end of the load hold to unloading rate (Feng and Ngan 2002 J. Mater. Res. 17 660; Tang and Ngan 2003 J. Mater. Res. 18 1141). Besides, the effect of creep on contact-depth measurement is considered. Removal of creep effects in both contact-area and contact stiffness measurement leads to satisfactory prediction of the dynamic hardness (Hd) and reduced modulus in β-Sn single crystals. The experimental results reveal that the measured hardness values exhibit a peak-load dependence, i.e. an indentation size effect (ISE). Such peak-load dependence is then analysed using the Meyer law, the Hays–Kendall approach, the proportional specimen resistance (PSR) model, the modified PSR (MPSR) model, and the Nix–Gao model. As a result, the modified PSR model is found to be the most effective one for Hd determination of β-Sn single crystals.

In this paper, analysis and interpretation of mechanical property measurements of β-SiAlON ceramic were reported. Indentation microhardness of β-SiAlON ceramic was measured using the Knoop and Vickers indenters. The analysis of the Vickers indentation microhardness data reveals the reverse indentation size effect that is the apparent microhardness increases with increasing applied indentation test load. However, the Knoop indentation microhardness data exhibit indentation size effect that is the apparent microhardness increases with decreasing applied test load. The experimental Knoop microhardness data was analyzed using Meyer's law, elastic-plastic deformation model, proportional specimen resistance model, and Hays-Kendall's model. As a result, modified proportional specimen resistance model is found to be the most effective one for the load-independent (H LI ) microhardness determination of the SiAlON ceramic. It was seen that different models used to analyze the data obtained from the Vickers indentation do not give the same intrinsic hardness value. We also present the calculation of the Young modulus, E, of the β-SiAlON ceramic.

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In this study, some mechanical properties of borided and unborided four steels were investigated. Boronizing of steels was performed by powder pack method at 1210 K for 4 h. The hardness of borides, boride layer thickness and room temperature tensile properties were measured and it was observed that hardness and tensile properties strongly depend on chemical composition of steels. In addition, the effect of a notch on impact behavior was examined by conducting the Charpy tests on borided and unborided steels. The greatest notch toughness was found for a steel AISI 316 with a microstructure consisting of different C, Ni and Cr chemical composition compared to AISI 1040, 1045 and 4140 steels.