共查询到19条相似文献,搜索用时 78 毫秒
1.
6000系Al-Mg-Si合金综合力学性能优良,具有比强度高、成型性能好、焊后表面质量高、耐腐蚀性好等特点,目前已经广泛应用于制造汽车车身板材。该系合金为可热处理强化合金,可以通过提高合金的时效响应速度,使合金在时效过程中获得尽可能大的强度提升。目前常用的措施是在合金中添加少量的Zn元素来促进时效析出,但Zn对合金时效析出相稳定性的影响却尚不明确。因此,本工作主要采用第一性原理计算的方法,计算了添加Zn的Al-Mg-Si合金中可能形成的Mg-Si相(包括Mg-Si GP区、β″相)和Mg-Zn相(包括Mg-Zn GP区、η′相)的晶格常数、形成焓。其中Mg2Si1Al3、Mg2Si3Al6、AlMg4Si6、Mg1Si1四种可能的Mg-Si GP区晶胞的形成焓从大到小为Mg2Si1Al3、Mg2... 相似文献
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用显微硬度测试、差示扫描量热法(DSC)和高分辨透射电镜(HRTEM)观察等手段研究了Al-Mg-Si合金人工时效过程中的硬化、组织变化以及早期析出相的演变。结果表明:在170℃时效的合金具有更高的峰值硬度。在时效初期晶内析出高数量密度的溶质原子团簇和GP区,合金的硬度显著提高。在170℃处理4 h后合金的硬度达到峰值,此时晶内析出相以针状β″相为主,β″相与Al基体界面三维共格应变是合金强化的主要原因。同时,晶界析出相呈断续分布状态。随着时效时间的增加β″相开始粗化,晶界析出相的连续程度降低。在过时效阶段晶内析出相的严重粗化和数量密度的降低,使合金的硬度剧烈降低。在时效的初始阶段,合金的析出序列为过饱和固溶体→球形原子团簇→针状GP区→针状β″相。 相似文献
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采用硬度测试和透射电镜研究Sn对不同Mg/Si比Al-Mg-Si合金时效硬化与析出行为的影响。结果表明:添加Sn虽然增加了低Mg/Si比合金峰值时效的析出相密度,但也降低了β″相的析出速度,从而降低了低Mg/Si比合金峰时效前的硬化速度和峰时效硬度。过时效阶段,含Sn合金的高析出相密度提高了低Mg/Si比合金过时效硬度。对于高Mg/Si比合金,添加Sn不仅增加合金的析出相密度,同时也提高了β″相的析出速度,从而增加了合金的硬化速度和峰时效硬度。 相似文献
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采用硬度测试、原位电阻测试及TEM等手段,研究了6101铝合金在175~195℃下时效析出相对相对电阻率(Δρ%)的影响,利用修正的马蒂森定则计算了175℃时不同时效时间析出相对相对电阻率的影响,得到了影响合金力学性能和导电率的温度时间判断依据。结果表明,随着温度的升高,时效初期团簇形成的时间越短,相对电阻率越低,硬度峰值也越低;175℃时效后期,析出相的密度增加,相间距减小,析出相对相对电阻率的影响基本稳定,导电率基本稳定。借助研究结果,确定了以力学性能优先和导电率优先的时效制度175℃/680min和195℃/220min,性能测试显示选取依据合理。 相似文献
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本文通过时效硬化曲线测量、室温拉伸实验以及时效组织的电镜观察,研究了 Li,Cu,Mg 等合金元素对 Al-Li 合金时效行为、显微组织和力学性能的影响。实验结果表明,增加 Li 的含量,提高合金强度,但降低延性。较高的 Cu,Mg 含量促进了 S′相的析出,减少共面滑移,使变形均匀,因而在提高强度的同时改善了合金的延性。 相似文献
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为了改善铝合金的力学性能,利用形变和时效工艺提高Al-3.5Cu-1.5Li-0.12Zr合金的强度和塑性.采用TEM观察和室温拉伸试验等手段,研究了形变量和时效工艺对含钪Al-3.5Cu-1.5Li-0.12Zr合金微观组织与拉伸性能的影响.结果表明,时效前的变形能促进T1(Al2CuLi)相弥散细小析出,显著提高合金强度,使时效峰值提前.合金强度随形变量和时效时间增加而增加,到峰值后,随形变量增加和时效时间的延长,T1相长大粗化,合金强度和塑性降低.该合金合宜的形变量和时效工艺为3.5%预变形和160℃/24 h时效. 相似文献
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通过分析时效期间Cu-Ni-Si合金显微硬度、导电率及微观组织的变化,研究了析出相和再结晶行为的相互作用,以期为该合金多级复合工艺的制定提供参考.研究发现,时效初期析出相对随后的再结晶过程具有强烈阻碍作用.在450、550℃较低温度时效时,合金发生原位再结晶,析出相在其体积分数略微升高或不变的情况下发生粗化;导电率上升趋势为先快后慢并趋于稳定,因而其变化曲线上无峰值出现;显微硬度则由于时效后期析出颗粒粗化,析出强化效果降低而出现峰值.在750℃高温时效时,合金发生不连续再结晶,析出相在体积分数略有降低的情况下发生粗化;导电率先快速上升后缓慢下降,因而出现峰值,而显微硬度由于析出物迅速粗化,一开始就表现为持续下降. 相似文献
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Cu-Cr-Zr-Y合金时效析出行为研究 总被引:8,自引:1,他引:7
研究了时效参数和变形量对 Cu 0. 39Cr 0.11 Zr 0. 41Y 合金性能的影响。结果表明合金经950℃×1h固溶后,在480℃时效可获得较高的导电率和硬度;时效前对合金施以冷变形可以加速时效初期第二相的析出,并显著提高其电导率和硬度,60%变形合金 480℃×2h时效处理后,导电率和显微硬度分别为83.32% IACS 和 161Hv,而固溶后直接时效仅为70.58%IACS和112Hv。微量稀土元素 Y的加入,使Cu 0. 39Cr 0. 11Zr 0. 41Y 合金的显微硬度比 Cu 0.41Cr 0.10Zr合金提高8~10Hv,导电率略有降低。 相似文献
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The impact of pre-shock loading on the precipitation reactions in an Al-Mg-Si alloy (AA6022) was studied by means of differential
scanning calorimetry (DSC), transmission electron microscopy (TEM) and hardness measurements. The samples were solutionized
and quenched in water prior to subsequent shock-loading and aging treatment. The TEM and DSC results show that, while shock-loading
prior to aging facilitated the precipitation of Q ′ and β, no significant effect on β′′ precipitates was observed. The hardness studies indicate that pre-shock loading strengthens
the material by forming a high concentration of microstructural defects, however the resultant mechanical properties of the
shocked sample are comparable to those without shock processing at the peak of aging. It was found that the rate of overaging
is higher in shocked samples, which is in agreement with the DSC and TEM results. 相似文献
12.
Effect of Si on the precipitation behavior of Mg-6Al alloy 总被引:2,自引:0,他引:2
Yizhen Lu Qudong Wang Xiaoqin Zeng Wenjiang Ding Yanping Zhu 《Journal of Materials Science Letters》2001,20(5):397-399
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M.E. Abd El-Azim 《Mechanics of materials : an international journal》1997,25(4):255-261
Incoloy alloy MA956 is an oxide dispersion hardened ferritic stainless steel produced by powder metallurgy. It is used as a candidate material for the high temperature components of gas turbines. This material underwent dynamic strain ageing at 300–400°C and strain rate of 1.2 × 10−3 s−1. The following features of dynamic strain aging were observed: serrated flow at 300 and 400°C, a peak in the ultimate tensile strength normalized by the elastic modules versus temperature curve at 400°C, a plateau in the 0.2% offset yield stress-temperature curve at 300–400°C, a peak in the deformation rate-temperature curve at 300°C and the elongation-temperature plot showed a minimum at 400°C associated with shear fracture and with a minimum in the reduction in area-temperature plot. These features of dynamic strain ageing were discussed in the view of the recent models of dynamic strain ageing. The effect of dynamic strain ageing on the deformation and fracture behavior of this material was discussed. 相似文献
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Effect of magnesium content on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castings 总被引:1,自引:0,他引:1
A study of the effect of magnesium concentration on the ageing behaviour as measured by the hardness of 380 alloy was conducted
for three levels of magnesium, namely 0.06 (base alloy), 0.33 and 0.5 wt%, for water-chilled castings (dendrite arm spacing
∼ 10–15 μm). Differential scanning calorimetry analysis of as-cast samples was carried out to determine the changes in the
reactions of the phases obtained during alloy solidification, employing heating rates of 0.1 and 1.0°Cs−1, up to approximately 700°C. Two heat treatments were applied to the as-cast alloys: T5 comprising ageing at 25 (room temperature),
155, 180, 200 and 220°C, for times up to 200 h, and T6 comprising solution heat treatment at 480 °C or 515°C for 8 h, followed
by quenching in warm water at 60°C, followed by immediate artificial ageing at 155 or 180°C for varying times up to 100h.
The results show that the higher hardness values obtained with T6 treatment can be explained by the excess precipitation of
magnesium-containing phases in the as-solidified alloys. This precipitation could be eliminated under the high cooling-rate
conditions prevalent in die-casting operations so that T5 treatment may be used to replace T6 treatment to produce the same
hardness values. In addition, solution heat treatment in the low-temperature range (480–515°C) is adequate to produce the
required changes in silicon morphology and dissolution of magnesium in the matrix. No significant difference in hardness behaviour
was observed when the magnesium content was increased beyond 0.3 wt%. 相似文献
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The effects of ageing treatments on transformation temperatures, hardness, and precipitation kinetics in a Cu-14.2Zn-8.5Al (wt%) shape-memory alloy were investigated. Quench-ageing treatment temperatures varied from 100 to 500° C with times up to 200 h after the solution treatment. The martensitic transformation temperature, M
s, of the hot-rolled material was decreased from 55 to 51 °C by the solution treatment. The temperature hysteresis (A
f-M
f) was 50° C for the hot-rolled condition, but was reduced to 30° C after the solution treatment. The maximum hardness for material aged at 500° C was lower than that for that aged at 300 or 400° C. The apparent activation energy for hardness increase in this alloy was 110 kJ mol–1, compared with 72 kJ mol–1 for the similar copper-based shape-memory alloy Cu-21.2 Zn- 6.0 Al. The ordering temperatures for B2 and DO3 superlattices were in the neighbourhood of 480 and 260° C, respectively. The tensile ductility and yield strength of this alloy were significantly reduced by the ageing treatment at 400° C. 相似文献
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《Scripta Metallurgica》1984,18(12):1365-1370
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Precipitation behavior of AlMgCu alloy during S phase aging sequence was studied with high resolution transmission electron microscope (HRTEM) and selected area diffraction (SAED) to determine the existence of S″ phase and GPBII zone in the alloy. Fast Fourier transform (FFT) patterns corresponding to GPB zones at different aging stages were observed, and it is revealed that S phase forms instantly after the GPB zone dissolves during aging. Both simulated HRTEM and SAED images illustrate that the S″ phase shows exactly the same characteristics as the S phase does, which is consistent with the experimental observations. A unique phase was also observed, which produced extra diffraction dots near the {012}Al positions in FFT pattern. This phase was once considered to be either S″ phase or GPBII zone, but none of them has been affirmed so far. In this work, it is found that the unique phase is a distorted and rotated S phase and that S″ phase or GPBII zone does not form during the aging. We further show that the S precipitation sequence of the aged AlMgCu alloy should be SSS → Cu–Mg clusters/GPB zone → S′/S(Al2CuMg). 相似文献