Papers by Keyword: 3DAP

Abstract: A Zn-added Al-Mg-Si-Cu alloy during aging at 170 °C up to 34 h exhibits an interesting age-hardening effect. Small clusters, enriched in Mg and Si, are present in the sample after 0.25 h aging. The β′′ phase is dominant with the peak hardness of 135 HV after aging of 8 h. A decrease in hardness of the alloy occurs with the aging time increasing to 34 h, due to the coarsening of β′′ phase. It is also found that the Cu-containing L phase co-exists with the β′′ phase at this aging condition. The quantitative solute concentrations of the matrix show that the formation of clusters is consistent with the slight lower contents of Mg, Si and Cu compared with the alloy chemical composition, and the present of β′′ and L phase is associated with the further partitioning of Mg, Si and Cu from the Al matrix into the precipitates. No Zn-rich clusters and precipitates are observed and the Zn concentration in matrix has no significant change during aging for up to 34 h. This result means that the major of Zn remains in the matrix as aging continues.

Abstract: In this work, Al-Mg-Si-Cu alloys for automotive body panels were designed and the related ageing behaviours were discussed in detail to help understand natural ageing and pre-ageing, as well as their influence on the subsequent paint-bake response. The clustering behavior of these Al-Mg-Si-Cu alloys in different ageing conditions was investigated by hardness / yield strength and electrical conductivity testing. The microstructure was investigated by using Electron Backscattered Diffraction (EBSD) technique, along with Scanning Electron Microscopy with Backscattered Electron Detector (BSE). The results show that the paint bake response is strongly influenced by the pre-ageing and natural ageing conditions. Both alloys show serrated yielding in a short natural ageing condition. Immediate high-temperature pre-ageing treatments were found to give a promising hardening response during the subsequent artificial ageing/ paint baking at 170^oC.

Abstract: The precipitation hardened steel 10Ni3MnCuAl after solution heat treatment and aging at 510 °C is investigated by three dimensional atom probe (3DAP). The results show that the Ni, Mn, Al and Cu distribute uniformly in the steel after solution heat treatment, but they form multicomponent precipitates after aging and cause the hardness increase. The concentration ratio between Ni and Al in multicomponent precipitates is roughly 1, while the concentration of Fe decreases, and the distance between concentration peak of Cu and those of Ni and Al becomes wider with the aging time, which is related to the precipitation character of Cu in α-ferrite.

Abstract: The aging hardened plastic mould steel 10Ni3MnCuAl after aging at 510 °C is investigated by scanning electron microscope (SEM), transmission electronic microscope (TEM) and three dimensional atom probe (3DAP). The results show that its microstructure is granular bainite after soluted. Its aging hardening is mainly due to the precipitation of a high density, nanoscale and fully coherent NiAl precipitation with the B2 structure for 4 h. Clusters associated precipitates from 3DAP results show that its aging hardening derives from multicomponent precipitate containing Fe, Ni, Al, Mn and Cu, and concentration of Fe decreases with the aging time, while that of Ni, Al, Mn and Cu are opposite, and the ratio between Ni and Al are roughly 1.

Abstract: The effects of Cu addition on precipitation characteristics in 6082 Al-Mg-Si alloy was investigated by means of DSC、TEM and 3DAP. It was found that addition of Cu has distinct effect on the precipitation and dissolution process of precipitates during heating by DSC measurement, the presence of Cu promotes the formation of GP zone or atomic clusters and accelerates the precipitation of β¢¢ . The precipitation sequence in the 6082 alloy with 0.6%Cu addition is as follows: SSSS atomic clusters/GP-zonesβ¢¢ + Q¢ Q¢.

Abstract: The effect of the copper additions on the heating process and the microstructure of 6082Al-Mg-Si alloys was investigated. The results show that there are four exothermic peaks from 50°C to 450°C in the Al-Mg-Si-0.6%Cu alloys, and the center temperature of every peak is lower than the temperature in the Al-Mg-Si alloys. Based on the observation of transmission electron microscope and three-dimensional atom probe, it is found that the copper reduce the precipitated time and the precipitated temperature of the precipitates. The number of the precipitates in the Al-Mg-Si-0.6%Cu alloys increased.

Abstract: An age-hardenable Cu-2.9%Ni-0.6%Si alloy was subjected to high-pressure torsion. Aging behavior was investigated in terms of hardness, electrical conductivity and microstructural features. Transmission electron microscopy showed that the grain size is refined to ~150 nm and the Vickers microhardness was significantly increased through the HPT process. Aging treatment of the HPT-processed alloy led to a further increase in the hardness. Electrical conductivity is also improved with the aging treatment. It was confirmed that the simultaneous strengthening by grain refinement and fine precipitation is achieved while maintaining high electrical conductivity. Three dimensional atom probe analysis revealed that fine precipitates with sizes of ~20 nm or smaller were formed in the Cu matrix and some particles consist of Ni and Si with no appreciable amount of Cu.

Abstract: Super304H, a Cu-containing 18Cr-9Ni-3CuNbN heat-resisting steel is wildly used as an superheater/reheater tube material for ultra-super-critical (USC) power plants all over the world. It is recognized that the Cu-rich phase is an important strengthening phase for Super304H. However, the detail precipitation behaviour and its strengthening effect are still not very clear. Investigated material was taken from routine production and was aged at 650°C for different times. The precipitation of Cu-rich phase in Super304H was studied by three dimensional atom probe (3DAP) and TEM. Experimental results show that Cu-rich clusters have been formed at very early stage of 650°C aging. The Cu-rich particle images have been clearly caught just after 650°C aging for 5h. The Cu atoms gradually concentrate to Cu-rich particles and the other elements (such as Cr, Ni etc) diffuse away from Cu-rich particles to γ-matrix with the increasing of aging time. The Cu-rich particle size and its density have been determined as a function of aging time. Cu-rich particles still keep nano-size and distribute homogenously in grains even after long time (1,000h) aging, which is one of the most important reasons for keeping good strength of Super304H heat-resistant steel at high temperatures.

Abstract: From the point of view of nitriding treatment(570°C), Cu precipitation is also occurred in the steel containing 1.3mass%Cu at this temperature. In this study, the behavior of nitriding in ultra low carbon steels containing Cr and/or Al and/or V are investigated. The following results are obtained : (1)After nitriding treatment the distribution of vickers hardness(Hv) differs in added nitriding element. (2)Profile of hardness in thickness is resulted from mainly precipitation hardening of nitride. (3)The high fatigue limit of nitrided steel is occurred by residual stress in vicinity of the surface. (4) Nitride precipitation is promoted by Cu precipitation that occurs in early stage of heat treatment.

Abstract: The formation of nanoclusters in the early aging stage is not fully clarified due to their extremely small sizes. To clarify the atomic-scale clustering of solute atoms, a three-dimensional atom probe (3DAP) analysis and a Monte Carlo computer simulation have been conducted together for Al-Zn alloys. The nanoclusters in the alloy aged at room temperature were successfully detected in the obtained 3DAP maps. From these maps the growth behavior of nanoclusters during aging was experimentally examined. In the Monte Carlo simulation, on the other hand, many-body nearest neighbor interactions between atoms and between atoms and a vacancy were taken into account. The Zn concentration of the clusters calculated in the 4-body interaction model best agreed with that obtained experimentally, suggesting the importance of many-body interactions. Therefore, it was confirmed that the combined analysis of 3DAP and the well-constructed Monte Carlo simulation is useful to make clear the nanocluster formation in alloys.