AE42和Mg-Al-RE-Ca合金的压入抗蠕变性能

用压入蠕变的方法研究了AE42合金和在AE41合金中加入0．4％-1．2％Ca的（质量分数，下同）Mg-Al-RE-Ca合金的抗蠕变性能，并利用光学显微镜，XRD和SEM（带EDS）对合金蠕变前后的组织结构进行了分析。结果表明：随着Ca添加量的提高，Mg-Al-RE-Ca合金的压入抗蠕变性能也不断提高，Mg-Al-RE-Ca合金在150℃和175℃时的压入抗蠕变性能优于AE42合金。压入蠕变前后的组织结构分析表明：AE42合金中Al11Nd3相在高温下不稳定会分解，造成抗蠕变性能下降：而在稀土含量相对少的Mg-Al-RE-Ca合金中，形成热稳定性好的Al2Ca，改善了合金的抗蠕变性能。     

Mg-4Al-RE-0．8Ca-0．8Si合金压入蠕变性能研究

用自制的装置对Mg-4Al-RE-0.8Ca-0.8Si(AECS410808)合金进行压入蠕变试验,用OM、SEM和EDS等方法对合金实验前后的组织成分进行分析.结果表明,AECS410808合金的稳态蠕变速率随温度或压力的增加而增大.稳态阶段的蠕变速率的对数lnε分别与应力的对数lnσ和温度倒数1/T均有较好的线件关系.在不同温度和应力条件下,合金的应力指数和蠕变表观激活能相差不大,其均值分别为n=3.04和Q=30.06 kJ/mol.AECS410808合金在稳态蠕变阶段的蠕变机制为晶界滑移主导的位错粘滞运动.合金中的Ca溶入β-Mg17Al12相中,提高了β的熔点,弥散分布的Mg2Si的枝臂伸入与其相邻的α-Mg晶粒内部,对晶粒产生了良好的钉扎作用,阻碍了晶界的滑移和佗错的运动,从而提高了合金的抗蠕变性能.     

添加Ca对Mg-4Sn合金组织演变和蠕变性能的影响（英文）

通过压入蠕变试验,研究Ca添加量(最高达4%,质量分数)对Mg-4Sn合金的显微组织和蠕变性能的影响。压入蠕变试验的操作温度为445⁴75K,归一化应力(σ/G,σ为应力;G为剪切模量)为0.0225⁰.035。利用光学显微镜和扫描电子显微镜对样品的显微组织进行研究。结果表明,Ca的加入量大于2%(质量分数)可抑制较不稳定Mg Sn2相的形成,从而使晶界处形成热稳定性较高的Ca-Mg-Sn相和Mg2Ca,提高Mg-4Sn合金的抗蠕变性能。根据压入蠕变试验所得的应力指数(6.04相似文献   

热处理状态对GH4698合金盘件组织和蠕变性能影响研究

开展了GH4698盘件后续热处理对盘件显微组织和蠕变性能影响研究以及GH4698盘件标准热处理下750 ℃的全阶段蠕变行为研究.试验结果表明:GH4698盘件标准热处理后的显微组织由晶内两种尺寸的球状γ'相和碳化物组成.增加第四段热处理后,显微组织有所变化,晶内小γ'相尺寸有所增加,晶界γ'相贫化区的宽度明显减小,晶界颗粒状碳化物析出更加完善.四段热处理后对GH4698盘件在750 ℃/382 MPa下的蠕变极限有利.GH4698合金750 ℃全蠕变曲线以及俄原型机盘件蠕变性能对比表明,GH4698合金在750 ℃稳态蠕变阶段较短,盘锻件的显微组织和晶粒度的不均匀会造成蠕变性能较大波动,合理的蠕变性能验收条件应为700 ℃/412 MPa/100 h下残余应变≤0.2%.     

AZ81镁合金压入蠕变性能

采用自制装置对AZ81镁合金进行压入蠕变实验,通过建立稳态压入蠕变本构模型分析合金的蠕变机制,利用扫描电镜(SEM)和X射线衍射(XRD)等方法研究合金蠕变前后的组织和成分。结果表明:压铸AZ81合金在稳态蠕变阶段的应力指数n为2.08,蠕变激活能QC为87.26 kJ/mol;蠕变诱导β相首先由非连续方式析出,到达一定程度后连续析出;沿晶界析出的β相导致合金抗蠕变性能降低;蠕变温度越高,基体和析出相的晶粒尺寸越大;压铸AZ81合金的压入蠕变机制为晶界扩散主导的位错交滑移运动。     

Mg和半固态加工对A356合金显微组织和抗蠕变性能的影响

研究Mg和半固态加工对A356合金蠕变性能的影响。结果表明：位错攀移控制的蠕变是占主导地位的蠕变机制,它不会受到半固态加工以及进一步添加 Mg 的影响。Mg 提高合金的抗蠕变性能主要是由于在枝晶间区域形成大量汉字型的 Mg2Si。半固态加工的样品表现出比铸造样品更好的抗蠕变性能,这是由于 Mg 在α(Al)相中显著溶解所致堆垛层错能的减少而导致的。     

低铌新锆合金的抗蠕变性能

通过对低铌新锆合金板材的蠕变性能数据和变形亚结构的分析,探讨了低铌新锆合金的蠕变过程及其抗蠕变性能.结果表明,①工业规模生产的1.4 mm厚的Zr-1Sn-0.3Nb-0.3Fe-0.1Cr合金板,在400℃,3种应力(117 MPa,137 MPa,157 MPa)条件下,200 h的蠕变,第2阶段的时间-应变关系分别为:117 MPa时,ε=0.24676 0.0189t(R=99.9%);137 MPa时,ε=1.95822 0.03417t(R=99.8%);157 MPa时,ε=6.17578 0.15793t(R=98.0%).②低铌新锆合金的蠕变速率远低于Zr-4合金.     

高温钼合金的蠕变性能与显微组织

德国一家金属专业研究所与奥地利Plansee公司合作对粉末冶金工艺生产的纯钼和TZM合金进行了高温蠕变行为和显微组织结构的研究。目的在于预测粉末冶金纯钼和TZM合金的变形特性，通过对结构的定量测定找出蠕变试验结果与显微组织演变的相关关系，同时建立2mm厚的Mo和TZM板材（这种板材已实现了工业化规模的生产）的有关蠕变性能资料。这些资料将会对认识这2种材料提供更全面的信息，从而能继续开发出一种既有很高的高温强度又具有极好的蠕变性能的钼合金。     

Ca和Sr对AE41合金压蠕变行为的影响

采用自制实验装置研究了ca和Sr对AE41(Mg-4A1-RE)合金高温压蠕变行为,并利用XRD和SEM对合金压蠕变前后的组织进行了分析.结果表明:在150℃和100 MPa条件下,添加一定量的Ca和Sr后合金的稳态蠕变速率和总蠕变量均小于AE41合金,改善了AE41合金的抗蠕变性能.铸态AE41合金由a-Mg基体和AI11Nd3相组成.在高温蠕变条件下,针状AI11Nd3相不稳定易发生分解,导致AE4l合金抗蠕变能力下降.在AE41合金中加入Ca和Sr后,针状Al11Nd3逐渐被Al2Ca、Al4Sr及少量的Al2Nd代替.分布在晶界的Al2Ca和Al4Sr有很高的热稳定性,提高了合金的抗蠕变性能.     

Ca对AE41合金压蠕变行为的影响

采用自制的实验装置研究了Ca对AE41(Mg-4Al-RE)合金压蠕变行为的影响,并利用光学显微镜、XRD和SEM(带EDX)对合金压蠕变前后的组织进行了分析.结果表明:在150℃、100 MPa条件下,随着Ca含量的增加,AEX(Mg-Al-RE-Ca)合金的第一阶段的压蠕变量、稳态蠕变速率及总蠕变量不断减小,抗蠕变性能不断提高.铸态AE41合金由α-Mg基体和Al11Nd3相组成.在高温蠕变条件下,因针状Al11Nd3相不稳定易发生分解,导致AE41合金抗蠕变能力下降.在AEAI合金中加人Ca后,针状Al11Nd3逐渐被Al2Ca和Al2Nd代替.分布在晶界的Al2Ca相有很高的热稳定性,提高了AEX合金的抗蠕变性能.     

Mechanical properties and microstructures of hot extruded AE42 alloy with addition of zinc

Mechanical properties and microstructures of AE42 magnesium alloy with addition of Zn and subjected to hot extrusion at 370 ℃ and an extrusion ratio of 8：1 were investigated. The results show that for the AE42 alloy, the addition of Zn can obviously improve its elongation as well as the ultimate tensile and yield strengths below 150 ℃. The addition of Zn can refine the mierostructure of the AE42 alloy, and result in the precipitation of Mg17Al12 and MgZn2 phases. Due to the addition of Zn to the AE42 alloy, the amount of Al11RE3 phase decreases, while the Al11RE3 phase becomes short rod-shaped from acicular and block, and distributes along the grain boundaries, which will have a stronger effect on the tensile properties of the alloy at elevated temperature. In addition, with the presence of MgZn2 precipitates, the sliding of grain boundaries is restrained and the strength of the alloy gets enhanced.     

Evolution of microstructure and hardness of AE42 alloy after heat treatments

The AE42 magnesium alloy was developed for high pressure die casting (HPDC) from low-aluminum magnesium alloys. In this alloy the rare earth (RE) elements were shown to increase creep resistance by forming Al_xRE_y intermetallics along the grain boundaries. The present work investigates the microstructure of squeeze cast AE42 magnesium alloy and evaluates its hardness before and after heat treatments. The change in hardness is discussed based on the microstructural observations. Some suggestions are given concerning future design of alloy compositions in order to improve high temperature creep properties even further. It is shown that the microstructure of the squeeze-cast AE42 alloy is stable at high temperature 450 °C. The subsequent solution and ageing treatments have a limited effect on the hardness. The weak age-hardening is attributed to the precipitation of small amount of Mg₁₇Al₁₂-phase with the use of about 0.7 wt.% aluminum. The heat treatment to achieve a maximum increase in the hardness is: solution treatment at 450 °C for 5–10 h followed by an ageing treatment at 190–220 °C for about 5 h.     

Microstructural modification and mechanical property improvement in friction stir zone of thixo-molded AE42 Mg alloy

Thixo-molded AE42 Mg alloy was friction stir welded, and the soundness of joints was evaluated, together with the microstructure evolution and mechanical properties in friction stir zones. According to X-ray radiography, the optimum FSW condition range of AE42 alloy exists between AZ61 and AZ31 alloys, and it seems that the optimum welding condition range increases with decreasing Al content in the Mg alloys. There are mainly two kinds of compounds in the thixo-molded AE42 alloy, and FSW has little influence on the grainy Al₁₀RE₂Mn₇ compound, but it has great influence on Al₁₁RE₃ phase, which is changed from lamellar eutectic to small particles after welding. Furthermore, the average diameter of Al₁₁RE₃ particles in SZ decreases with increasing the traveling speed at constant rotation speed due to less heat input. The hardness in SZ is higher than that in BM, and tensile strength and elongation are both improved after welding because the stirring refines and uniforms the microstructure and intermetallic compounds.     

稳定化热处理对Zn-10Al-2Cu-0.02Ti合金组织及蠕变行为的影响

采用扫描电子显微镜、透射电镜、电子探针以及X射线衍射物相分析等技术手段,对稳定化热处理前后Zn-10Al-2Cu-0.02Ti合金的显微组织进行观察,通过室温恒载荷拉伸、慢应变速率拉伸实验研究合金组织变化及其对合金室温蠕变行为的影响.结果表明:经过稳定化热处理((350℃,30 min,水冷)+(100℃,12h, 空冷)),后合金中的α+η层片状组织的减少,胞状和粒状组织增多;与挤压态合金相比,经过稳定化热处理后的Zn-10Al-2Cu-0.02Ti合金的抗蠕变性能显著提高,其稳态蠕变速率降低了96.9％.     

The effect of creep aging on localized corrosion resistance of AA2060 alloy

The influence of creep aging at varied stresses on the localized corrosion behavior of AA2060 has been studied in this paper. Samples were subjected to stress free aging (SFA) and creep aging (CA) under two stress levels, after which tensile tests and intergranular corrosion (IGC) tests were carried out. The corrosion morphology and depth were examined using optical microscope. Compared with SFA, CA can enhance the mechanical properties and increase the IGC resistance of Al–Cu–Li alloy but high-stress CA would intensify the intragranular corrosion penetration in the first 25 hr of aging time. The microstructure observation results show that dislocations introduced by CA provide favorable nucleation sites for T1 precipitates in the grain and impede the growth of T1 precipitates at grain boundary. Therefore, the potential difference between the grain interior and grain boundary can be reduced compared to that for the SFA. The mechanism by which CA affects the corrosion resistance of Al–Cu–Li alloys, as is essential to understand and optimize the creep aging process, has been proposed by considering the effect of creep-deformation-induced dislocations.     

ZL107合金的高温静态蠕变和循环蠕变

研究了不同热处理状态的ZL107合金在107℃的高温静态蠕变和循环蠕变的行为。结果发现：峰时效下，合金的蠕变抗力强于过时效状态下材料的蠕变抗力。 循环蠕变时材料表现出蠕变减速现象。经峰时效处理的ZL107合金在循环蠕变中表现出较静态蠕变低的激活能，用非热空位机制进行了解释，而经过时效处理的ZL107合金表现出高的激活能，滞弹性机制起了重要作用。     

热处理对DZ125定向凝固合金组织结构与蠕变行为的影响

通过不同条件蠕变性能测试及组织形貌观察,研究了热处理对DZ125合金的组织结构演变和蠕变行为的影响规律。结果表明,铸态合金的枝晶间区域存在较多放射状的共晶组织,在枝晶间和枝晶干处部分γ′相呈蝶形形态且γ′相尺寸具有较大差异。铸态合金的共晶组织及γ′相在固溶过程中被溶解,并在随后的冷却过程中类菱形的细小γ′相自γ基体中析出;一次时效期间,类菱形的细小γ′相发生钝化并长大直至转变成立方体形态;二次时效期间,γ′相的尺寸基本不变,但立方度增加,合金的组织结构为γ′相以共格方式自γ基体中析出。在热处理过程中基本消除了合金中的共晶组织,并提高了γ′相的立方度,但并未消除合金中的组织不均匀性,枝晶干区域的立方γ′相尺寸细小,而枝晶间区域的立方γ′相尺寸粗大,并且合金在980 ℃具有良好的抗蠕变性能。     

Compressive creep behavior of Mg-Sn binary alloy

Mg-Sn based alloy is one of the potential alloys for application at elevated temperature.The compressive creep behavior of ageing-treated Mg-xSn(x=3%,5%) alloys was investigated at the temperatures of 423 and 473 K and the stresses from 25 MPa to 35 MPa.When the tin content varies,the ageing-treated Mg-xSn alloys show quite different creep resistance,which are mainly attributed to the size and distribution of Mg_2Sn phases in the ageing-treated Mg-xSn alloys.The calculated value of stress exponent, n=6.3...