无碳化物贝氏体钢 (CFB):第二部分
双辊铸轧镁合金的机械性能
选择性激光烧结 (SLS):第二部分
DataPLUS 模块提供上万种金属材料和非金属材料的腐蚀数据、焊接性能、尺寸与公差信息以及涂层信息。 点击这里了解更多。
Total Materia New Application Launch! 2021年1月14日
Total Materia New Application Launch! 2021年2月10日
Total Materia New Application Launch! 2021年3月10日
在使用Total Materia几个月之后,以及深刻体验过所有潜在功能之后,我非常感谢你们的卓越工作和持续稳定的升级服务。 Total Materia始终是用来达成这一目的唯一工具。
M. Manfredini Bonfiglioli Industrial Gearmotors 博洛尼亚, 意大利
我们的目标很简单,就是让 Total Materia成为全球工程师在材料领域的首选一站式解决方案
Prof. Dr. Viktor Pocajt, CEOKey to Metals AG
A study of age hardening of three commercial purity Al-Cu-Mg alloys shows that the formation of Cu-Mg clusters coincides with the rapid hardness increase during natural ageing. It is also shown that the yield strength can be accurately described by a model incorporating modulus hardening originating from the difference in modulus between Al and Cu-Mg clusters and solution strengthening.
The second rapid hardening reaction is smaller than the first one and this is likely to be due to the tendency for recovery at the aging temperature. These aging times correspond to: immediately after the rapid hardening, at the end of the hardness plateau and peak hardness, respectively.
Since solutes are uniformly distributed in the matrix after aging for 1 min, the initial rapid hardening cannot be attributed to the homogenous precipitation of GPB zones or to a uniform dispersion of Cu-Mg co-clusters. However, evidence for Cu-Mg co-clusters is observed after 60 min aging at 200°C and GPB zones are clearly observed by the 3DAP after 480 min at 200°C. This indicates that GPB zones are readily detectable by the 3DAP when present in the matrix, and we therefore conclude that there are no GPB zones formed after the initial rapid hardening.
Furthermore, the results indicated that the formation of GPB zones is associated with the onset of the second stage of hardening. The GPB zones observed in these alloys are thought to evolve from the Cu-Mg co-clusters through a continuous growth process similar to that involving Mg-Ag co-clusters observed recently in Al-Cu-Mg-Ag alloys and that involving Mg-Si co-clusters in Al-Mg-Si alloys.
Wilson and Partridge reported that the dislocation loops and helices formed during quench lower the nucleation barrier of the S phase particles and cause the precipitation of the S phase in the early stage of aging. This suggests that solute atoms rapidly diffuse to the dislocations during aging, where nucleation of the S phase occurs rapidly.
Since the dislocations also act as vacancy sinks, the number of the quenched-in vacancies would decrease significantly in the matrix phase, thereby retarding the kinetics of homogeneous or uniform precipitation of GPB zones in the matrix. This would seem to explain the very long incubation period preceding GPB zone formation. It is noteworthy that in many age hardenable aluminum alloys, GP zones usually precipitate spontaneously in uniform dispersions after brief aging treatments.
The retarded kinetics of the zone formation in the present Al-Cu-Mg alloys may be accounted for by the rapid annihilation of the quenched-in vacancies. The existence of the wide PFZ near the heterogeneously nucleated S precipitates indicates a depletion of solute and vacancies near the dislocations and is interpreted as further evidence for a preferred solute-dislocation affinity.
As mentioned above, the 5% deformation on the rapidly hardened specimen caused further rapid hardening at 150°C and this strongly suggests that solute-dislocation interaction is one of the main reasons for the rapid hardening. The occurrence of plastic instabilities in the deformation of Al-Mg alloys is well known to relate to the tendency of Mg atoms to diffuse to dislocations, producing a dynamic strain aging effect.
Recently, Chinh et al. also reported this effect in dilute binary Al-Cu alloys in the as-quenched condition. These results support the proposal that a solute-dislocation interaction can influence significantly the mechanical properties of aluminum alloys.
While the present results indicate that a solute-dislocation interaction causes the first stage of strengthening, rather than a uniform dispersion of Cu-Mg co-clusters, it is also clear that such clusters do form during the later stages of the aging sequence. Moreover, the presence of a uniform dispersion of Cu-Mg co-clusters was detected prior to the observation of GPB zones and it is almost certain that these clusters evolve into GPB zones as they grow in size and increase in order. The formation of these microstructural constituents produces the second stage of hardening.
Room temperature age hardening mechanisms of commercial purity Al-1.2Cu-1.2Mg-0.2Mn and Al-1.9Cu-1.6Mg-0.2Mn (wt%) alloys were studied by hardness testing, DSC, isothermal calorimetry and 3DAP analysis. In the two alloys, hardening at room temperature occurs between about 0.5h and 20h at room temperature, and subsequently hardness remains constant.
3DAP analysis showed that after a short time of natural ageing Cu-rich clusters are present, and on further room temperature ageing Cu-Mg clusters form. During the room temperature hardening, the density of clusters increases and the Cu:Mg ratio in the clusters approaches unity. DSC and isothermal calorimetry shows that the formation of Cu-Mg clusters coincides with a substantial exothermic heat release.
The microstructural analysis shows that the formation of Cu-Mg clusters coincides with the rapid hardness increase during natural ageing. The kinetics of cluster formation is analysed, and the results indicate that, even though the kinetics of Cu-Mg cluster formation will involve detailed 29 atomistic interactions, it can be described well as a classical nucleation and growth process.
It is also shown that the yield strength (converted from hardness data) of these two alloys can be accurately described by a model incorporating modulus hardening originating from the difference in modulus between Al and Cu-Mg clusters and solution strengthening.
The following conclusions have been reached:
2. No evidence for the presence of solute clusters has been obtained immediately after the rapid hardening reaction. The co-clustering of Cu and Mg was observed towards the end of the hardness plateau and these clusters are thought to evolve into GPB zones during the second stage of the age-hardening process. Thus, the initial rapid hardening is not caused from uniformly dispersed clusters of solute.
3. A further rapid hardening reaction was observed when the rapidly hardened specimen was re-aged after deformation. This indicates that the rapid hardening is related to a solute-dislocation interaction. We propose that solute segregation to the existing dislocations causes dislocation locking due to a solute-dislocation interaction and that this is the origin of the initial rapid hardening.
Date Published: Sep-2010
输入搜索词:
搜索项
全文 关键字
标题 摘要
本文属于一系列文章。点击下面的链接,你可以看到有关这个话题的更多文章。
Heat treatment diagrams are available for a huge number of materials in the Total Materia database.
Heat treatment diagrams covering hardenability, hardness tempering, TTT and CCT can all be found in the standard dataset.
To select materials by special properties, you can use the special search check boxes in the Advanced Search module.
To define the search criteria, all you have to do is select the country/standard of interest to you from the ‘Country/Standard’ pop-up list and to check ‘Heat Treatment Diagram’ box, situated in the Special Search area of the form in the lower part of the Advanced Search page.
Click Submit.
After selecting the material of interest to you, click on the Heat Treatment link to view data for the selected material. The number of heat treatment records is displayed in brackets next to the link.
All available heat treatment information will then be displayed for the chosen material.
For you’re a chance to take a test drive of the Total Materia database, we invite you to join a community of over 150,000 registered users through the Total Materia Free Demo.