Y 对8090Al-Li 合金拉伸性能和断裂行为的影响

研究了两种不同 Y 含量对8090Al-Li 合金拉伸性能及断裂行为的影响。实验表明:加入0.1wt-%Y 可在不降低强度的情况下提高合金的塑性,加入0.5wt-%Y 可在不降低塑性的情况下提高合金的强度。在峰值时效条件下,不加 Y 的合金断裂为穿晶韧窝型和沿晶塑性混合方式,并伴有沿晶二次裂纹,加0.1%Y 不改变合金断裂模式,但使沿晶成分减少;加0.5%Y 合金则发生快速剪切断裂。本文从晶粒结构角度对断裂行为提出了解释。     

Mg含量对亚快速凝固Al-Zn-Mg-Cu-Zr合金组织与性能的影响

利用OM,DSC,XRD及SEM等分析方法,研究了Mg含量对亚快速凝固方式铸造Al-Zn-Mg-Cu系合金组织和力学性能的影响。结果表明,提高Mg含量会使合金中非平衡共晶相数量和晶界面积增加,枝晶臂间距减小,晶粒相对细化。Mg含量提高使合金强度得到提高,但塑性下降。合金中Mg含量的增加还导致固溶处理后残余第二相的数量增加并降低均匀化效果。     

Y对8090Al—Li合金拉伸性能和断裂行为的影响

研究了两种不同Ｙ含量对８０９０Ａｌ－Ｌｉ合金拉伸性能及断裂行为的影响。实验表明：加入０．１ｗｔ－％Ｙ可在不降低强度的情况下提高合金的塑性，加入０．５ｗｔ－％Ｙ可在不降低塑性的情况下提高合金的强度。在峰值时效条件下，不加Ｙ的合金断裂为穿晶韧窝型和沿晶塑性混合方式，并伴有沿晶二次裂纹，加０．１％Ｙ不改变合金断裂模式，但使沿晶成分减少；加０．５％Ｙ合金则发生快速剪切断裂。本文从晶粒结构角度对断裂行为提…     

Al-2.55Li-1.01Mg合金的变形与断裂行为研究

本文研究了不同时效状态下Al—2.55Li—1.01Mg合金的变形与断裂行为,并结合显微组织进行了分析。结果表明:在固溶态和短时间时效状态下,合金的断裂主要是共面滑移导致的穿晶断裂;在长时间时效状态下,合金的断裂主要是晶界弱化造成的沿晶断裂。     

时效温度对含准晶相Mg93Zn6Y1合金的组织及性能影响

采用光学显微镜、扫描电子显微镜和X射线衍射及能谱分析,研究了铸态、固溶处理及在不同温度下时效处理的Mg93Zn6Y1合金的显微组织。发现铸态Mg93Zn6Y1合金显微组织主要由α-Mg和I相组成。经过固溶处理后,晶界处准晶相发生熔断,由铸态下的连续网状结构变为颗粒状。在不同的时效温度下,晶界处颗粒状准晶相长大且α-Mg晶内出现颗粒状准晶相。随着时效温度的升高,颗粒状准晶相发生长大,逐渐变为多边形状或鱼骨状。时效温度为300℃时,合金中准晶相大部分以颗粒状均匀分布在基体上。通过硬度及耐腐蚀性能测试,发现时效处理可大幅提高合金的硬度及耐腐蚀性能。其中,时效温度为300℃时效果最佳。     

合金元素对 Al-Li 合金时效行为和力学性能的影响

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。     

时效制度对挤压+锻造工艺路线FGH95粉末高温合金组织和性能的影响

采用不同的时效制度处理热等静压+挤压+等温锻造工艺的FGH95合金,并对处理后合金的显微组织和力学性能进行了系统研究。结果表明,经过双级时效(870℃/1 h,AC+650℃/24 h,AC)和单级时效(760℃/10 h,AC)处理后,合金的晶粒度无明显差异,但γ′相的数量、尺寸及分布存在显著差异。相比于单级时效,双级时效可以更有效地促进晶内γ′相粗化,晶内γ′相平均直径达到78 nm,而单级时效为67 nm;同时,双级时效更有利于M 3B 2等晶间强化相的析出。二者的拉伸强度水平相当,但双级时效合金的持久寿命低于单级时效合金,而其持久塑性要优于单级时效合金。     

Zn/Mg比及时效温度对Al-Zn-Mg-Cu系合金析出行为的影响

采用热力学模拟软件中的铝合金模块研究了Al-Zn-Mg-Cu系合金中不同Zn/Mg比及时效温度对析出相GP区及η'相的析出规律的影响。结果表明,GP区含量随Zn/Mg比的增加而降低,低温时效能够促进GP区的形成;而η'相含量随Zn/Mg比的增加略微降低,时效温度对η'相含量影响不大;与120℃相比,合金在160℃时效时η'相含量达到6.5%的时间缩短16 h;在相同温度下时效时,随Zn/Mg比的增加,η'相含量达到6.5%的时间先缓慢增加,当Zn/Mg比大于2.91时则快速增加。合金的淬火敏感性随Zn/Mg比的增加有所降低;随Zn/Mg比从2.46提高到3.20,GP区和η'相的鼻尖温度分别从150℃和330℃降低到140℃和320℃;临界冷却速率随Zn/Mg比的增加而逐渐降低。     

Si对Al-Mg-Cu合金时效析出行为的影响

向不同镁含量的Al-Mg-Cu合金中添加Si元素,研究Si对该合金时效强化行为的影响,并在此基础上探究自然时效处理对合金后续人工时效行为的影响.研究结果表明,在2.0％Mg的基础上添加0.15 wt％Si可以显著增强合金的人工时效强化效果,但是合金强度随Si含量的进一步增加而增加的幅度较小;Si对合金的时效强化效果是由...     

循环温度场作用下时效态TC4合金的拉伸性能及组织

对时效状态不同的ＴＣ４合金在７７￣６２３Ｋ间进行了热循环试验，测定了热循环前后的拉伸性能。结果表明：热循环１０００次后，近峰时效态合金的强度下降，过时效态合金的强度变化最小，而塑性均显著下降。合金中的位错密度、层错和形变孪晶的数量增多。在热循环过程中α相内激活的位错以｛０１１０｝〈２１１０〉型为主，激活的孪晶以｛１０１１｝型为主。     

Microstructure and fatigue properties of Mg-to-steel dissimilar resistance spot welds

The structural application of lightweight magnesium alloys in the automotive industry inevitably involves dissimilar welding with steels and the related durability issues. This study was aimed at evaluating the microstructural change and fatigue resistance of Mg/steel resistance spot welds, in comparison with Mg/Mg welds. The microstructure of Mg/Mg spot welds can be divided into: base metal, heat affected zone and fusion zone (nugget). However, the microstructure of Mg/steel dissimilar spot welds had three different regions along the joined interface: weld brazing, solid-state joining and soldering. The horizontal and vertical Mg hardness profiles of Mg/steel and Mg/Mg welds were similar. Both Mg/steel and Mg/Mg welds were observed to have an equivalent fatigue resistance due to similar crack propagation characteristics and failure mode. Both Mg/steel and Mg/Mg welds failed through thickness in the magnesium sheet under stress-controlled cyclic loading, but fatigue crack initiation of the two types of welds was different. The crack initiation of Mg/Mg welds was occurred due to a combined effect of stress concentration, grain growth in the heat affected zone (HAZ), and the presence of Al-rich phases at HAZ grain boundaries, while the penetration of small amounts of Zn coating into the Mg base metal stemming from the liquid metal induced embrittlement led to crack initiation in the Mg/steel welds.     

镁的氢化反应对氢化燃烧合成储氢合金Mg2NiH4纯度的影响

本文主要通过改变在镁氢化反应温度的保温时间,研究不同合成压力、合成温度下,中间反应-镁的氢化反应对氢化燃烧合成Mg2NiH4的影响.初步探讨了镁的氢化反应与燃烧合成Mg2Ni反应及其氢化反应的内在联系.研究结果表明:镁的充分氢化在促进Mg-Ni燃烧合成反应的同时有效地提高了Mg2Ni的氢化活性,这一结果为工业化低压合成纯Mg2NiH4提供了可行途径,但在低温下仅延长镁的氢化时间,产物中少量的Ni很难消除.     

Effect of High‐Energy Ball Milling on Mechanical Properties of the Mg–Nb Composites Fabricated through Powder Metallurgy Process

New biocompatible and biodegradable Mg–Nb composites used as bone implant materials are fabricated through powder metallurgy process. Mg–Nb mixture powders are prepared through mechanical milling and manual mixing. Then, the Mg–Nb composites are fabricated through cold press and sintering processes. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of Mg–Nb composites are investigated. The mechanical milling process is found to be effective in reducing the size of Mg and Nb particles, distributing the Nb particles uniformly in the Mg matrix and obtaining Mg–Nb composite particles. The Mg–Nb composite particles can be bound together firmly during the sintering process, result in Mg–Nb composite structures with no intermetallic formation, lower porosity, and higher mechanical properties compared to composites prepared through manual mixing. Interestingly, the mechanical properties of manually mixed Mg–Nb composites appear to be even lower than that of pure Mg.

     

Role of secondary phase in microstructural stability of as-extruded Mg–Sn–Ca at high temperature

The microstructural stability in three as-extruded Mg alloys (Mg–0.6Ca, Mg–1.9Sn and Mg–1.9Sn–0.6Ca) at high temperature (673?K) is studied by optical microscope (OM), scanning electron microscopy (SEM), and its effect on the mechanical properties is tested by tensile test. The grain size of Mg–1.9Sn–0.6Ca alloy is retained at high temperature, while grains in Mg–0.6Ca grow at some degree and in Mg–1.9Sn they coarsen seriously. Additionally, the tensile strength of Mg–1.9Sn–0.6Ca is also most thermally stable. The outstanding microstructural and mechanical stability of as-extruded Mg–1.9Sn–0.6Ca alloy is attributed to the strong pinning effect of stable CaMgSn secondary phase. The poor performances of Mg–0.6Ca and Mg–1.9Sn are due to the dissolution of Mg₂Ca and Mg₂Sn particles, respectively.     

Mg/NiTi复合材料的制备及阻尼性能

采用Mg粉的无压熔渗法制备Mg/NiTi复合材料以提高多孔NiTi合金的强度和阻尼性能。通过OM、SEM、EDS和XRD分析Mg/NiTi复合材料的显微组织结构,采用压缩实验分析其抗压强度、吸能能力,采用热机械分析仪分析其内耗和存储模量。结果表明:经Mg粉无压熔渗后,多孔NiTi合金的孔隙被Mg填充,其孔隙率由原来的50.38%下降至5.6%,且Mg与NiTi合金的界面结合良好。多孔NiTi合金主要由B2奥氏体相和B19'马氏体相及少量Ni₃Ti相和NiTi₂相组成;Mg/NiTi复合材料除增加了熔渗的Mg相外,还新生成了Mg₂Ni相。Mg的渗入未改变多孔NiTi合金相变行为,但提高了相变温度。Mg/NiTi复合材料的抗压强度可达554 MPa,较多孔NiTi合金提高了61%,压缩断裂方式也由多孔NiTi合金的孔壁崩塌断裂转变为Mg/NiTi复合材料的剪切断裂。Mg/NiTi复合材料的吸能较多孔NiTi合金有大幅提高。同时,Mg/NiTi复合材料的内耗值有所增加,而存储模量大幅提高,整体呈现出更佳的阻尼性能。      

CNT-reinforced AlSi10Mg composite by selective laser melting: microstructural and mechanical properties

Carbon nanotube (CNT)-AlSi10Mg composites were fabricated by selective laser melting (SLM). The influence of CNTs on the density, microstructure, and strength of SLM CNT-AlSi10Mg composites was investigated. The addition of CNTs over 0.1?wt-% significantly damaged the density due to the high surface energy of the CNTs. The network Si eutectic had no significant difference in either the SLM AlSi10Mg alloy or the CNT-AlSi10Mg composite. Reserved CNTs with a short scale were observed in the SLM CNT(0.5?wt-%)-AlSi10Mg composite. The ultimate tensile strength of the 0.05?wt-% CNT-AlSi10Mg composite was 441.2?±?0.9?MPa, which was higher than that of AlSi10Mg alloy. The grain boundary strengthening played an important role in the reinforcement of CNT-AlSi10Mg composite because of the refined grain.     

Mg2Si薄膜的磁控溅射制备及表征

采用直流磁控溅射的方法在Si(100)衬底上制备了Mg2Si外延半导体薄膜。通过XRD和FESEM对Mg2Si薄膜的晶体结构和表面形貌进行了表征,分析了溅射功率对Mg2Si薄膜制备的影响,得到了Mg2Si薄膜在不同溅射功率下的外延生长特性。结果表明,在Si(100)衬底上,Mg2Si薄膜具有(220)的择优生长特性,并且在50~80W的溅射功率范围内,随着溅射功率的增加,Mg2Si外延薄膜的衍射峰强度逐渐增强。     

Wetting and adhesion at Mg/MgO interfaces

The wetting of (100), (110), and (111) MgO single crystals by molten Mg was studied in a flowing Ar atmosphere at 1073 K using an improved sessile drop method. The results show that the contact angle and work of adhesion are mildly dependent on MgO substrate orientation. However, the work of separation calculated by density functional theory shows a sequence of (100) < (110) < (111). This discrepancy was explained by a model considering the possible effects of evaporation and deposition of Mg at the substrate surface on the interfacial adhesion. For Mg on the clean MgO surfaces, the adhesion consists primarily of Mg–O ionic bonds with some Mg–Mg metallic bonds. In addition, a small amount of covalent bonds are present in the metal slab adjacent to the Mg/MgO (110) and Mg/MgO (111) interfaces. The different work of separation at three interfaces depends on the strength and amounts of Mg–O and Mg–Mg bonds as well as on the surface free energy of respective planes. For the MgO surfaces pre-deposited by a monolayer of Mg atoms, the interfaces are dominated by the Mg–Mg bonds, thus mitigating the effect of substrate orientation on the wettability and adhesion.     

Mg2Si／Si异质结的制备

采用射频磁控溅射和低真空退火方法制备Mg2Si／Si异质结,首先在n型Si（111）衬底上沉积Mg膜,经低真空退火形成Mg2Si／Si异质结,Mg膜厚度约为484nm,退火后形成的Mg2Si薄膜厚度约400nto,利用xRD和sEM分别研究了Mg2Si薄膜的晶体结构和表面形貌,霍尔效应结果表明,制备的Mg2Si薄膜呈现n型导电特性。     

Ca3-xMg2+xNi13合金的储氢性能

为了弄清Mg含量对Ca3Mg2Ni13型化合物结构参数和储氢性能的影响,利用X射线衍射研究了Ca3-xMg2+x,Ni13(x=0.5,1.0和1.5)合金的相结构,并采用Sieverts型设备测量了其P-C-T曲线.研究表明,Mg在Ca3Mg2Ni13型化合物中的最大固溶度接近于Ca1.5Mg<,3.5>Ni13合金中的Mg含量.固溶的Mg含量增加导致化合物点阵常数减小,这可以有效地改善吸放氢热力学性能,其中Ca2Mg3Ni13吸、放氢的焓变分别为-28,30 kJ/mol H2.此外,Ca2Mg3Ni13在吸放氢循环过程中不发生氢致非晶化和氢致分解,因而具有良好的循环稳定性.