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Papers by Hanis Ayuni Mohd Yusof

Acta Materialia, 2016

The role of boron in conferring the grain boundary character in a new polycrystalline superalloy ... more The role of boron in conferring the grain boundary character in a new polycrystalline superalloy suitable for power generation applications is considered. One boron-free and three boron-containing variants are studied using a suite of high resolution characterisation techniques including atom probe tomography (APT), high resolution secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The primary effect of boron addition is the suppression of Cr-rich M23C6 carbide and the formation instead of the Cr-rich M5B3 boride. The SIMS analysis indicates that the boride particles are distributed fairly uniformly along the grain boundaries, of length up to 500 nm along the grain boundary. The substantial majority of the boron added resides in the form of these M5B3 borides; some boron segregation is found at the γ′/M5B3 interfaces but interfaces of other forms-such as γ/γ′, γ/M5B3, γ/MC and γ′/MCshow no significant segregation. Creep testing indicates that the optimum boron content in this alloy is 0.05 at.%.

Defect and Diffusion Forum, 2009

It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate... more It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate than the conventional boronizing process (CB). This process was conducted on duplex stainless steel (DSS) which exhibit superplasticity. The study concentrated on the effect of strain rate and compression strain on SPB. The process was conducted under four different strain rates and three diferent strains condition. Boronizing was successfully conducted with the best result obtained under the high strain rate range of 5 x 10-5 s-1 to 1 x 10-3 s-1 which is associated with the superplastic region. Through SPB, movement of atoms into the specimen was highly accelerated by the grain boundary sliding process leading to a formation of thick and hard boronized layer in extraordinarily short period of time.

Materials Science and Engineering: A, 2011

MATEC Web of Conferences, 2014

Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons f... more Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons for its effect and the optimum quantities which need to be added are not well understood. Recently, some of the authors have developed a new corrosion-resistant single crystal superalloy for power generation applications which has a good balance of mechanical properties and resistance to environmental degradation. Here, this same alloy system is studied but in the polycrystalline state with additions of boron and carbon. The influence of boron on creep behaviour has been quantified and rationalised, with an emphasis on the grain boundary phase transformations which occur. NanoSIMS is utilised to investigate the segregation of boron at grain boundaries, with SEM used to characterise the effect of boron on the precipitation of Cr 23 C 6 type carbides at grain boundaries. When the boron content increases, the agglomeration of M 23 C 6 carbides at grain boundaries is inhibited. Uniformly distributed discrete M 23 C 6 carbides are observed at higher boron content, whereas a deleterious film of M 23 C 6 along the grain boundaries arises as the boron concentration is reduced. Boron promotes also the formation of γ layers at the grain boundaries.

The role of boron in conferring the grain boundary character in a new polycrystalline superalloy ... more The role of boron in conferring the grain boundary character in a new polycrystalline superalloy suitable for power generation applications is considered. One boron-free and three boron-containing variants are studied using a suite of high resolution characterisation techniques including atom probe tomography (APT), high resolution secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The primary effect of boron addition is the suppression of Cr-rich M 23 C 6 carbide and the formation instead of the Cr-rich M 5 B 3 boride. The SIMS analysis indicates that the boride particles are distributed fairly uniformly along the grain boundaries, of length up to 500 nm along the grain boundary. The substantial majority of the boron added resides in the form of these M 5 B 3 borides; some boron segregation is found at the g 0 /M 5 B 3 interfaces but interfaces of other forms e such as g/g 0 , g/M 5 B 3 , g/MC and g 0 /MC e show no significant segregation. Creep testing indicates that the optimum boron content in this alloy is 0.05 at.%.

Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons f... more Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons for its effect and the optimum quantities which need to be added are not well understood. Recently, some of the authors have developed a new corrosion-resistant single crystal superalloy for power generation applications which has a good balance of mechanical properties and resistance to environmental degradation. Here, this same alloy system is studied but in the polycrystalline state with additions of boron and carbon. The influence of boron on creep behaviour has been quantified and rationalised, with an emphasis on the grain boundary phase transformations which occur. NanoSIMS is utilised to investigate the segregation of boron at grain boundaries, with SEM used to characterise the effect of boron on the precipitation of Cr23C6 type carbides at grain boundaries. When the boron content increases, the agglomeration of M23C6 carbides at grain boundaries is inhibited. Uniformly distributed discrete M23C6 carbides are observed at higher boron content, whereas a deleterious film of M23C6 along the grain boundaries arises as the boron concentration is reduced. Boron promotes also the formation of γ' layers at the grain boundaries.

In this work, SPB of duplex stainless steel (DSS) under compression method is studied with the ob... more In this work, SPB of duplex stainless steel (DSS) under compression method is studied with the objective to produce ultra hard and thick boronized layer using minimal amount of boron powder and at a much faster boronizing time as compared to the conventional process. SPB is conducted under dual compression methods. In the first method DSS is boronized using a minimal amount of boron powder under a fix pre-strained compression condition throughout the process. The compression strain is controlled in such a way that plastic deformation is restricted at the surface asperities of the substrate in contact with the boron powder. In the second method, the boronized specimen taken from the first mode is compressed superplastically up to a certain compressive strain under a certain strain rate condition. The process in the second method is conducted without the present of boron powder. As compared with the conventional boronizing process, through this SPB under dual compression methods, a much harder and thicker boronized layer thickness is able to be produced using a minimal amount of boron powder.► Superplastic boronizing. ► Dual compression method has been developed. ► Hard boride layer. ► Bulk deformation was significantly thicker the boronized layer. ► New data on boronizing could be expanded the application of DSS in industries.

In this work, a further study on boronizing using compression method called superplastic boronizi... more In this work, a further study on boronizing using compression method called superplastic boronizing (SPB) was conducted. This process was conducted on duplex stainless steel (DSS) that exhibited superplasticity. Efforts were being put in obtaining ultra hard surface through SPB by focusing on the boron powder particle size. The microstructure, hardness, and layer thickness of the boronized materials were investigated. Comparison using as-received DSS with coarse microstructure also was performed. The overall results from the study showed that the SPB process can produced a very hard surface of close to 4000 HV and significantly improved the surface properties of the DSS.

It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate... more It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate than the conventional boronizing process (CB). This process was conducted on duplex stainless steel (DSS) which exhibit superplasticity. The study concentrated on the effect of strain rate and compression strain on SPB. The process was conducted under four different strain rates and three diferent strains condition. Boronizing was successfully conducted with the best result obtained under the high strain rate range of 5 x 10 -5 s -1 to 1 x 10 -3 s -1 which is associated with the superplastic region. Through SPB, movement of atoms into the specimen was highly accelerated by the grain boundary sliding process leading to a formation of thick and hard boronized layer in extraordinarily short period of time.

Acta Materialia, 2016

Defect and Diffusion Forum, 2009

Materials Science and Engineering: A, 2011

MATEC Web of Conferences, 2014

The role of boron in conferring the grain boundary character in a new polycrystalline superalloy ... more The role of boron in conferring the grain boundary character in a new polycrystalline superalloy suitable for power generation applications is considered. One boron-free and three boron-containing variants are studied using a suite of high resolution characterisation techniques including atom probe tomography (APT), high resolution secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). The primary effect of boron addition is the suppression of Cr-rich M 23 C 6 carbide and the formation instead of the Cr-rich M 5 B 3 boride. The SIMS analysis indicates that the boride particles are distributed fairly uniformly along the grain boundaries, of length up to 500 nm along the grain boundary. The substantial majority of the boron added resides in the form of these M 5 B 3 borides; some boron segregation is found at the g 0 /M 5 B 3 interfaces but interfaces of other forms e such as g/g 0 , g/M 5 B 3 , g/MC and g 0 /MC e show no significant segregation. Creep testing indicates that the optimum boron content in this alloy is 0.05 at.%.

Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons f... more Boron is used as a grain boundary strengthener in the nickel-based superalloys, but the reasons for its effect and the optimum quantities which need to be added are not well understood. Recently, some of the authors have developed a new corrosion-resistant single crystal superalloy for power generation applications which has a good balance of mechanical properties and resistance to environmental degradation. Here, this same alloy system is studied but in the polycrystalline state with additions of boron and carbon. The influence of boron on creep behaviour has been quantified and rationalised, with an emphasis on the grain boundary phase transformations which occur. NanoSIMS is utilised to investigate the segregation of boron at grain boundaries, with SEM used to characterise the effect of boron on the precipitation of Cr23C6 type carbides at grain boundaries. When the boron content increases, the agglomeration of M23C6 carbides at grain boundaries is inhibited. Uniformly distributed discrete M23C6 carbides are observed at higher boron content, whereas a deleterious film of M23C6 along the grain boundaries arises as the boron concentration is reduced. Boron promotes also the formation of γ' layers at the grain boundaries.

It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate... more It was reported that superplastic boronizing process (SPB) provides a much faster boronizing rate than the conventional boronizing process (CB). This process was conducted on duplex stainless steel (DSS) which exhibit superplasticity. The study concentrated on the effect of strain rate and compression strain on SPB. The process was conducted under four different strain rates and three diferent strains condition. Boronizing was successfully conducted with the best result obtained under the high strain rate range of 5 x 10 -5 s -1 to 1 x 10 -3 s -1 which is associated with the superplastic region. Through SPB, movement of atoms into the specimen was highly accelerated by the grain boundary sliding process leading to a formation of thick and hard boronized layer in extraordinarily short period of time.