Autonomous Repair Mechanism of Creep Damage in Fe-Au and Fe-Au-B-N Alloys

The autonomous repair mechanism of creep cavitation during high-temperature deformation has been investigated in Fe-Au and Fe-Au-B-N alloys. Combined electron-microscopy techniques and atom probe tomography reveal how the improved creep properties result from Au precipitation within the creep cavities, preferentially formed on grain boundaries...

Thermal-history dependent magnetoelastic transition in (Mn,Fe)2(P,Si)

The thermal-history dependence of the magnetoelastic transition in (Mn,Fe)2(P,Si) compounds has been investigated using high-resolution neutron diffraction. As-prepared samples display a large difference in paramagnetic-ferromagnetic (PM-FM) transition temperature compared to cycled samples. The initial metastable state transforms into a lower...

Moment evolution across the ferromagnetic phase transition of giant magnetocaloric (Mn,Fe)2(P,Si,B) compounds

A strong electronic reconstruction resulting in a quenching of the Fe magnetic moments has recently been predicted to be at the origin of the giant magnetocaloric effect displayed by Fe2P-based materials. To verify this scenario, x-ray magnetic circular dichroism experiments have been carried out at the L edges of Mn and Fe for two typical...

High-resolution X-ray diffraction investigation on the evolution of the substructure of individual austenite grains in TRIP steels during tensile deformation

The martensitic transformation behaviour of the metastable austenite phase in low-alloyed transformation-induced plasticity (TRIP) steels has been studied in situ using high-energy X-ray diffraction during deformation. The austenite stability during tensile deformation has been evaluated at different length scales. A powder diffraction analysis...

Tuning the phase transition in transition-metal-based magnetocaloric compounds

Neutron-diffraction experiments on the (Mn,Fe)2(P,Si)-type compounds have shown a site preference of Si atoms in the hexagonal structure. The degree of ordering of Si depends on the Si/P ratio, while it is independent of the Mn/Fe ratio. The ferromagnetic-paramagnetic magnetoelastic transition is closely related to the size of the magnetic...

Position-dependent shear-induced austenite– martensite transformation in double-notched TRIP and dual-phase steel samples

While earlier studies on transformation-induced-plasticity (TRIP) steels focused on the determination of the austenite-to-martensite decomposition in uniform deformation or thermal fields, the current research focuses on the determination of the local retained austenite-to-martensite transformation behaviour in an inhomogeneous yet carefully...

Taming the first-order transition in giant magnetocaloric materials

Large magnetically driven temperature changes are observed in MnFe(P,Si,B) materials simultaneously with large entropy changes, limited (thermal or magnetic) hysteresis, and good mechanical stability. The partial substitution of B for P in MnFe(P,Si) compounds is found to be an ideal parameter to control the latent heat observed at the Curie...

Self healing by Cu precipitation in deformed Fe-Cu-B-N-C

Steels are among the most widely used construction materials as their mechanical properties can be tuned over a very wide range of desired combinations of strength formability and other properties. However, when exposed for long times to high temperatures steel components can exhibit premature and low-ductility creep fracture, which arises from...

Self healing by Cu precipitation in deformed Fe-Cu-B-N-C

Steels are among the most widely used construction materials as their mechanical properties can be tuned over a very wide range of desired combinations of strength formability and other properties. However, when exposed for long times to high temperatures steel components can exhibit premature and low-ductility creep fracture, which arises from...

Enhancing the creep life of steels by self-healing through dynamic in-service precipitation

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Effect of carbon on copper precipitation in deformed Fe-based alloys studied by positron annihilation spectroscopy

The role of deformation-induced defects and carbon addition on the copper precipitation during aging at 550 oC is investigated in high-purity Fe-Cu-B-N-C alloy samples by Coincidence Doppler Broadening. In samples with 0% and 8% cold pre-strain, the influence of tensile pre-deformation on the precipitation kinetics of copper is studied. The...

High/low-moment phase transition in hexagonal Mn-Fe-P-Si compounds

Using high-resolution neutron diffraction measurements for Mn-rich hexagonal Mn-Fe-P-Si compounds, we show that the substitution of Mn for Fe on the 3f sites results in a linear decrease of the Fe/Mn(3f) magnetic moments, while the Mn(3g) magnetic moments remain constant. With increasing temperature, the Mn(3g) magnetic moments show almost no...

Positive muon spin rotation and relaxation measurements on the ferromagnetic superconductor UGe2 at ambient and high pressure

Results of a detailed investigation of the ferromagnetic superconductor UGe2 using positive muon spin rotation and relaxation techniques are presented. The pressure and temperature dependences of the frequencies and related spin-spin relaxation rates show that the transition from the weakly to the strongly polarized magnetic (WP-SP) phases is...