Indentation

About: Indentation is a research topic. Over the lifetime, 13002 publications have been published within this topic receiving 340476 citations.

Local mechanical properties of the 6061-T6 aluminium weld using micro-traction and instrumented indentation

Abstract: The local mechanical properties of a weld zone, in a 6061-T6 aluminium alloy subjected to the modified indirect electric arc technique have been studied. The mechanical properties of the base metal, the weld metal and the heat affected zone were determined by means of usual and instrumented indentation testing, as well as micro-traction testing. To analyse the heat input effect resulting from the welding process, the evolution of the weld zone size was evaluated by means of classical indentation under a constant applied load. The results were presented using a Vickers hardness map representation. This allows monitoring exact hardness variation while leading to the identification of the different zones of the welded joint. Instrumented indentation testing was carried out to determine the local mechanical properties, such as the yield stress, the bulk modulus and the strain-hardening exponent. Obtained results are compared to those derived from tensile tests conducted on micro-specimen cuts taken from the weld zone. It was observed that yield stress values are directly comparable for indentation and micro-traction experiments. As for the elastic properties, no comparison was possible since the bulk modulus is measured by indentation, whereas it is the Young's modulus by tensile test. The micro-traction testing seems to be more sensitive to represent the work hardening of a material since the corresponding exponent is found to be constant by instrumented indentation.

The effect of the substrate on the mechanical properties of tin coatings

Abstract: TiN coatings are commonly used in industry to impart improved friction and wear performance. It is widely recognised that the substrate plays an important role in determining the mechanical properties and wear resistance of such coatings. TiN coatings are usually applied to hard tool steels where there is substantial load support from the substrate. However, there are many applications where it may be desirable to apply the coatings to substrates with lower hardness or stiffness values than the conventional, hard tool-steel substrates that are commonly used. Coatings can still be effectively used in these applications. However, it is then critical to understand the transitions between where the deformation is contained solely in the coating and where it is a combination of coating/substrate properties that are important in determining the overall mechanical response of the system. This paper therefore reports on a systematic investigation of the effect of the substrate on the mechanical response using a range of mechanical testing techniques. A TiN coating was deposited using ion-assisted PVD onto a number of substrates with differing combinations of modulus and hardness [i.e. a range of Young's modulus (E) to yield stress (Y) E/Y ratios]. The mechanical properties of these coatings have been investigated using nanoindentation, microindentation and scratch testing, and the deformation was observed using scanning electron microscopy. In the microindentation tests, nested cracks were observed around the indentations. In the nanoindentation tests, the indentation response was found to be plasticity-dominated, with little evidence of cracking. The scratch tests showed that the scratch response was controlled by plastic deformation in the substrate, and that the friction coefficient increased as the depth of penetration into the sample increased. For the coatings here, it was observed that the indentation depth/coating thickness ratio required for the deformation to be contained within the coating was less than the usual t/10 ratio.