Mertens I Anne | Université de Liège (original) (raw)

Papers by Mertens I Anne

Journal of Materials Engineering and Performance, 2012

Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight... more Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight reduction, but their production can be impaired by the poor wettability of C substrates by Mg. In this study, a new ''liquid'' processing route has been investigated. By making use of the well-known effect of a pre-treatment of the C fibers with an aqueous solution of K 2 ZrF 6 in favoring spontaneous wetting of C with Al, C yarns have been pre-impregnated with Al and the feasibility of further using them as reinforcements in Mg matrix composites has been assessed. More particularly, it has thus been shown that the, under the thermal conditions involved in the process, C fibers did not suffer damage due to chemical reaction with Al, and also that special care should be taken to control the surface condition of the pre-infiltrated yarns.

liquid state methods such as squeeze casting is usually impaired by the poor wettability of C sub... more liquid state methods such as squeeze casting is usually impaired by the poor wettability of C substrates by liquid Mg. As a consequence, solid state processes such as Friction Stir Processing (FSP) appear as very promising alternative C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ductile which is on the other hand capable of precipitation hardening thus allowing for an improvement of the mechanical behaviour after processing.

Materials & Design, 2015

Laser cladding is a metal deposition technique used to fabricate or repair components made from h... more Laser cladding is a metal deposition technique used to fabricate or repair components made from high value metallic alloys. In the present work Ti-6Al-4V deposits with variable thickness are made to assess the use of laser cladding as a repair technology. Both the effect of the building strategy (BS) and the incident energy (IE) on the metallurgical characteristics of the deposits in relation to their complex thermal history have been studying. It is shown that for the configuration consisting in a decreasing track length (DTL) under high IE, a gradient of cooling rate exists that leads to the presence of different phases within the microstructure. Conversely homogeneous microstructures are present either for the configuration with a constant track length (CTL) under high IE, and for the strategy obtained from a DTL under low IE. Depending on the possible heat accumulation the nature of the phases are determined together with hardness maps within the deposits. Some qualification criteria are set prior to tensile tests to selected the adequate candidate-deposit that does not weaken the cladded material when it is stressed. A thermo-metallurgical scheme is proposed that helps in understanding the effect of both the BS and the IE on the microstructure.

Materials Science Forum, 2013

In this study, samples of alloy Ti-6Al-4V have been processed by different additive manufacturing... more In this study, samples of alloy Ti-6Al-4V have been processed by different additive manufacturing techniques in order to compare the resulting microstructure. In all three processes, ultrafast cooling gives rise to strongly out-of-equilibrium microstructures. However, the specificities of the heat flow in each process lead to significant differences as far as the grains orientation and the resulting microstructural anisotropy are concerned.

ISIJ International, 2001

The influence of heat-treating conditions on the retention of carbon-enriched austenite of TRIP-a... more The influence of heat-treating conditions on the retention of carbon-enriched austenite of TRIP-assisted multiphase steel grades containing different amounts of silicon and/or aluminium is investigated. The ensuing mechanical properties resulting from the TRIP ...

ABSTRACT A new solid-state process developed recently on the same principles as Friction Stir Wel... more ABSTRACT A new solid-state process developed recently on the same principles as Friction Stir Welding (FSW), Friction Stir Processing appear as a very promising technique for the production of metal matrix composites and for tailoring materials properties. In the present work, this process has been applied to two different composite systems:(i) magnesium-matrix composites reinforced with carbon fibers, and (ii) copper-matrix composites reinforced with Y2O3 powder. Process optimization and mechanical ...

Journal de Physique IV (Proceedings), 2003

ABSTRACT TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced tr... more ABSTRACT TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilisation of austenite is made possible by the combination of appropriate chemical composition (containing classically high levels of silicon, or, as developed more recently, aluminium) and of a two-step heat treatment comprising an intercritical annealing followed by an isothermal holding in the bainite formation range. A detailed understanding of the effects of Si and Al on the bainite transformation kinetics is thus of primary importance for the optimisation of austenite retention. The present study aims at a better knowledge of the influence of aluminium on the kinetics of the bainite transformation of intercritical austenite, as compared to the effect of silicon. The bainite transformation kinetics was followed by dilatometry in a set of 6 steel grades with varying aluminium and silicon contents. These dilatometry experiments were coupled with a characterisation of the microstructures by X-ray diffraction, SEM and image analysis. Il was shown that aluminium has a less pronounced effect than silicon in retarding the bainite transformation.

Le Journal de Physique IV, 2001

... Moyer and Ansell (1975) showed that the importance of the volume expansion depends on the car... more ... Moyer and Ansell (1975) showed that the importance of the volume expansion depends on the carbon content of austenite. Therefore, we used the relationship proposed by Moyer and Ansell (1975) to estimate the diameter ...

In this work, an evaluation method to calculate the austenite fraction during continuous heating ... more In this work, an evaluation method to calculate the austenite fraction during continuous heating and isothermal annealing from dilatometric data is proposed. By means of a single reference measurement to determine a scaling factor correcting for experimental errors, a ...

Journal of Materials Engineering and Performance, 2012

Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight... more Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight reduction, but their production can be impaired by the poor wettability of C substrates by Mg. In this study, a new ''liquid'' processing route has been investigated. By making use of the well-known effect of a pre-treatment of the C fibers with an aqueous solution of K 2 ZrF 6 in favoring spontaneous wetting of C with Al, C yarns have been pre-impregnated with Al and the feasibility of further using them as reinforcements in Mg matrix composites has been assessed. More particularly, it has thus been shown that the, under the thermal conditions involved in the process, C fibers did not suffer damage due to chemical reaction with Al, and also that special care should be taken to control the surface condition of the pre-infiltrated yarns.

liquid state methods such as squeeze casting is usually impaired by the poor wettability of C sub... more liquid state methods such as squeeze casting is usually impaired by the poor wettability of C substrates by liquid Mg. As a consequence, solid state processes such as Friction Stir Processing (FSP) appear as very promising alternative C fabric stacked between two sheets of either the ductile Mg alloy AZ31B, or of the less ductile which is on the other hand capable of precipitation hardening thus allowing for an improvement of the mechanical behaviour after processing.

Materials & Design, 2015

Laser cladding is a metal deposition technique used to fabricate or repair components made from h... more Laser cladding is a metal deposition technique used to fabricate or repair components made from high value metallic alloys. In the present work Ti-6Al-4V deposits with variable thickness are made to assess the use of laser cladding as a repair technology. Both the effect of the building strategy (BS) and the incident energy (IE) on the metallurgical characteristics of the deposits in relation to their complex thermal history have been studying. It is shown that for the configuration consisting in a decreasing track length (DTL) under high IE, a gradient of cooling rate exists that leads to the presence of different phases within the microstructure. Conversely homogeneous microstructures are present either for the configuration with a constant track length (CTL) under high IE, and for the strategy obtained from a DTL under low IE. Depending on the possible heat accumulation the nature of the phases are determined together with hardness maps within the deposits. Some qualification criteria are set prior to tensile tests to selected the adequate candidate-deposit that does not weaken the cladded material when it is stressed. A thermo-metallurgical scheme is proposed that helps in understanding the effect of both the BS and the IE on the microstructure.

Materials Science Forum, 2013

In this study, samples of alloy Ti-6Al-4V have been processed by different additive manufacturing... more In this study, samples of alloy Ti-6Al-4V have been processed by different additive manufacturing techniques in order to compare the resulting microstructure. In all three processes, ultrafast cooling gives rise to strongly out-of-equilibrium microstructures. However, the specificities of the heat flow in each process lead to significant differences as far as the grains orientation and the resulting microstructural anisotropy are concerned.

ISIJ International, 2001

The influence of heat-treating conditions on the retention of carbon-enriched austenite of TRIP-a... more The influence of heat-treating conditions on the retention of carbon-enriched austenite of TRIP-assisted multiphase steel grades containing different amounts of silicon and/or aluminium is investigated. The ensuing mechanical properties resulting from the TRIP ...

ABSTRACT A new solid-state process developed recently on the same principles as Friction Stir Wel... more ABSTRACT A new solid-state process developed recently on the same principles as Friction Stir Welding (FSW), Friction Stir Processing appear as a very promising technique for the production of metal matrix composites and for tailoring materials properties. In the present work, this process has been applied to two different composite systems:(i) magnesium-matrix composites reinforced with carbon fibers, and (ii) copper-matrix composites reinforced with Y2O3 powder. Process optimization and mechanical ...

Journal de Physique IV (Proceedings), 2003

ABSTRACT TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced tr... more ABSTRACT TRIP-assisted steels show enhanced mechanical properties thanks to the strain-induced transformation of retained austenite to martensite (TRIP effect). Stabilisation of austenite is made possible by the combination of appropriate chemical composition (containing classically high levels of silicon, or, as developed more recently, aluminium) and of a two-step heat treatment comprising an intercritical annealing followed by an isothermal holding in the bainite formation range. A detailed understanding of the effects of Si and Al on the bainite transformation kinetics is thus of primary importance for the optimisation of austenite retention. The present study aims at a better knowledge of the influence of aluminium on the kinetics of the bainite transformation of intercritical austenite, as compared to the effect of silicon. The bainite transformation kinetics was followed by dilatometry in a set of 6 steel grades with varying aluminium and silicon contents. These dilatometry experiments were coupled with a characterisation of the microstructures by X-ray diffraction, SEM and image analysis. Il was shown that aluminium has a less pronounced effect than silicon in retarding the bainite transformation.

Le Journal de Physique IV, 2001

... Moyer and Ansell (1975) showed that the importance of the volume expansion depends on the car... more ... Moyer and Ansell (1975) showed that the importance of the volume expansion depends on the carbon content of austenite. Therefore, we used the relationship proposed by Moyer and Ansell (1975) to estimate the diameter ...

In this work, an evaluation method to calculate the austenite fraction during continuous heating ... more In this work, an evaluation method to calculate the austenite fraction during continuous heating and isothermal annealing from dilatometric data is proposed. By means of a single reference measurement to determine a scaling factor correcting for experimental errors, a ...