Glass and glass-ceramic coatings, versatile materials for industrial and engineering applications

Among various coating systems for industrial and engineering applications, glass and glass-ceramic coatings have advantages of chemical inertness, high temperature stability and superior mechanical properties such as abrasion, impact etc as compared to other coating materials applied by thermal spraying in its different forms viz. PVD, CVD, plasma, etc. Besides imparting required functional properties such as heat, abrasion and corrosion resistance to suit particular end use requirements, the glass and glass-ceramic coatings in general also provide good adherence, defect free surface and refractoriness. Systematic studies covering the basic science of glass and glass-ceramic coatings, the functional properties required for a particular end-use along with the various fields of application have been reviewed in this paper.     

SiC w/BAS复合材料的显微结构及力学性能的研究

本文采用热压烧结法制备出致密的SiCw增强BAS玻璃陶瓷基复合材料．结果表明,BAS基体晶化后获得以钡长石为主晶相和莫来石为次晶相的复相BAS玻璃陶瓷．晶须的加入对BAS基体有显著的强韧化效果,加入30vol％SiCw可使材料的室温抗弯强度和断裂韧性分别由基体的156MPa和1．40MPa·m1/2提高到356MPa和4．06MPa·m1/2．TEM观察结果表明,晶须／基体界面结合良好,无界面反应物和非晶层的存在．断口形貌和压痕裂纹扩展路径的SEM观察结果表明,复合材料的主要增韧机制为裂纹偏转、晶须的拔出和桥接．     

聚酰亚胺/SiO_2杂化膜的微观结构与力学性能

以聚酰亚胺(HQDDA-0DA)为基体,正硅酸乙酯(TEOS)为增强剂,在共溶DMF中,通过溶胶-凝胶法,制备出厚度约为20μm,不同含量SiO2的PI/SiO2杂化膜,用Fr-IR、SEM及万能拉力实验机对膜材料的微观结构和力学性能表征.结果表明,杂化膜中Si-OH和PI存在化学键;10%SiO2含量的杂化膜SiO2颗粒呈卵形镶嵌在PI基体中,取向与膜平行,随着SiO2含量的增加,颗粒尺寸增大,30%SiO2含量的杂化膜中,无机相形成部分的连续结构,并出现团聚;10%SiO2含量的杂化膜强度和模量均为最大,随着SiO2含量的进一步增加的膜的强度与模量均下降.     

SiCw/BAS复合材料的显微结构及力学性能的研究

本文采用热压烧结法制备出致密的SiC_w增强BAS玻璃陶瓷基复合材料．结果表明,BAS基体晶化后获得以钡长石为主晶相和莫来石为次晶相的复相BAS玻璃陶瓷．晶须的加入对BAS基体有显著的强韧化效果,加入30vol％SiC_w可使材料的室温抗弯强度和断裂韧性分别由基体的156MPa和1．40MPa·m^1/2提高到356MPa和4．06MPa·m^1/2．TEM观察结果表明,晶须／基体界面结合良好,无界面反应物和非晶层的存在．断口形貌和压痕裂纹扩展路径的SEM观察结果表明,复合材料的主要增韧机制为裂纹偏转、晶须的拔出和桥接．     

牙科热压技术对新型玻璃陶瓷微观结构和化学稳定性的影响

实验的目的是分析牙科热压技术对新型二硅酸锂玻璃陶瓷微观结构和化学稳定性的影响.对Li2O-SiO2-K2O-Al2O3-Zr02-P2O2玻璃系统进行晶化热处理,应用牙科热压技术制备化学稳定性测试试件.X射线衍射(XRD)分析热压前后玻璃陶瓷的物相组成,扫描电镜(SEM)观察微观结构,根据ISO6872标准测试材料的化学稳定性.结果表明,热压前后玻璃陶瓷的晶相组成均以二硅酸锂(Li2Si2O5)为主,热压后,主峰强度增高,晶体尺寸增大,并且呈现沿热压方向的定向排列趋势.热压前后玻璃陶瓷的化学稳定性均符合ISO6872标准要求,热压组试件对化学腐蚀有较强的抵抗性.牙科热压技术能够改变实验玻璃陶瓷的微观结构,进而提高材料的化学稳定性.     

Microstructure and mechanical properties of as-deposited and heat-treated additive manufactured 9Cr steel

Wire arc additive manufacturing technology has been applied to fabricate 9Cr ferritic/martensitic steel. The steel is widely used in the power industries because of good performances. The effects of different heat treatment conditions on microstructure, hardness, tensile properties, and Charpy impact toughness were investigated. The results show that the microstructure of the as-deposited condition consists of untempered lath martensitic with high strength and low toughness. It was found that heat treatment can change the microstructure characteristics. Moreover, samples after heat treatment have been observed with high elongation and impact toughness but relatively low hardness and tensile strength. The better combination of strength, ductility and microstructure were obtained for the normalising temperature of 1323?K and tempering temperature of 1033?K.     

Microstructure evolution and mechanical properties of friction stir welded FeCrNiCoMn high-entropy alloy

To investigate the microstructural development and mechanical properties of friction stir welded high-entropy alloy, the stirring process and the air cooling period were separated for discussion. The texture component developed from A* {111}<112> to A {111}<110> in the stirring stage, and finally changed to B {112}<110> in the subsequent air cooling stage caused by the multiple mechanisms including discontinuous dynamic recrystallization, continuous dynamic recrystallization, static recovery and selected grain growth. This work also demonstrated that the static recovery and the selected grain growth during the air cooling stage remarkably deteriorated the microstructure and mechanical properties which is produced during the stirring stage, and it cannot be neglected when investigating the microstructure transformation and mechanical properties during the friction stir welding.     

电磁铸造5182铝合金锭的组织与性能研究

采用电磁铸造技术铸造了易拉罐用5182变形铝合金，采用光学显微镜和扫描电镜分析了其显微组织，而且对其进行了均匀化处理和对比实验。结果表明，电磁铸造锭有更加良好的内部组织和优良的力学性能，电磁铸造试样的硬度大约是普通连续铸造试样的两倍，疲劳性能是普通连续铸造铸锭的3倍，电磁铸造铸锭还有良好的耐磨性，电磁铸造锭的优良性能得宜于电磁搅拌的作用使整个铸锭获得均匀细小的晶粒组织，电磁铸造技术是一种无模铸造技术，它依靠电磁力约束液体金属成型，液体金属不与铸模接触，铸锭表面光滑如镜；相反，普通连续铸造锭表面因存在振动痕和亚表面偏析等铸造缺陷，力学性能大大降低。     

超声振动作用下镁-钢焊缝组织演变及力学性能研究

本文旨在通过引入超声振动辅助,实现镁合金和镀锌钢的可靠连接,扩大镁-钢复合构件应用范围。本文在镁合金与镀锌钢的TIG熔钎焊过程中引入超声波振动,并通过金相显微镜、扫描电镜、硬度计和拉伸机等设备对镁-钢接头微观组织和力学性能进行检测,研究超声波功率对镁合金/镀锌钢接头质量的影响。实验结果表明:超声波振动辅助焊接工艺可以有效改善镁/钢接头的焊缝成形,消除接头熔焊区域的气孔等缺陷。研究表明:在焊接过程中引入1 000 W功率进行超声振动后,接头熔焊区的平均晶粒尺寸由初始的51 μm下降到23.2 μm,晶粒细化效果显著;超声振动辅助焊接工艺改善了接头钎焊区反应层的形态,使钎焊区MgZn反应层厚度更均匀,并可以提高接头熔焊区的显微硬度;当超声波功率为1 000 W时,接头力学性能达到3 735 N,相比未施加超声波振动的接头(3 270 N),力学性能提高了14.2%。超声振动辅助工艺可以有效改善镁/钢焊缝的显微组织,提高接头力学性能,实现镁/钢异种金属的可靠连接。     

Enhancement of mechanical properties of a soft magnetic Fe-based metallic glass

In this study, the effect of non-isothermal partial crystallisation on microstructure, and mechanical and magnetic properties of (Fe_0.9Ni_0.1)₇₇Mo₅P₉C_7.5B_1.5 BMG was investigated. Microstructural characterisations revealed that there was a phase separation in the as-cast BMG. Formation of nano-crystalline phases first occurred in the separated amorphous phase during initial stages of crystallisation process and then continued in the matrix phase. The nanocrystalline/amorphous matrix composite exhibited higher mechanical and magnetic properties compared to those of the as-cast BMG.     

TI-6Al-4V合金置氢-除氢组织与力学性能

为研究除氢处理对置氢钛合金组织与性能的影响,对Ti-6Al-4V合金在不同参数条件下进行了置氢与除氢处理,采用光学显微镜分析了置氢-除氢处理过程中Ti-6Al-4V合金微观组织的演化规律,通过室温拉伸试验研究了置氢-除氢处理后Ti-6Al-4V合金的力学性能,探讨了Ti-6Al-4V合金置氢-除氢组织与力学性能之间的相...     

Microstructure and mechanical properties of Mg-Al-Zn alloy under a low-voltage pulsed magnetic field

Effect of a low-voltage pulsed magnetic field on the solidified microstructure and mechanical properties of Mg-Al-Zn alloy has been investigated. When the low-voltage pulsed magnetic field is applied during solidification, the as-cast microstructure is significantly refined and α-Mg is modified from developed dendrite to fine rosette. This morphology modification is caused by the accumulation of Joule heat on the dendrite tip. The yield strength is improved with the application of the low-voltage pulsed magnetic field under normal casting and semi-continuous casting conditions. The ultimate tensile strength is decreased slightly under normal casting condition due to the occurrence of plenty of shrinkage under the low-voltage pulsed magnetic field. The shrinkages are removed and the yield strength and ultimate tensile strength are increased under semi-continuous casting condition with low-voltage pulsed magnetic field.     

反应溅射Ti-Al-Si-N纳米晶复合薄膜的微结构与力学性能

采用Ar、N2和SiH4混合气体反应溅射制备了一系列不同Si含量的Ti-Al-Si-N薄膜，并采用EDS、AES、XRD、TEM和微力学探针研究了薄膜的微结构和力学性能。结果表明通过控制混合气体中SiH4分压可以方便地获得不同Si含量的Ti-Al-Si-N纳米晶复合薄膜。当Si含量达到3．5％(原子分数)时，薄膜中出现TiSix界面相，造成(Ti，Al)N晶粒细化，使薄膜力学性能得到提高，硬度和弹性模量的最高值分别为36．0GPa和400GPa。进一步提高Si含量，薄膜的力学性能逐渐降低。     

新型Ti-650合金电子束焊接头组织及性能研究

采用电子束对新型耐650 ℃使用的高温钛合金板材进行焊接,并进行1 000 ℃/1 h/AC+700 ℃/4 h/AC的退火处理,研究了接头的组织、硬度分布,母材和接头的拉伸性能和持久性能.结果表明,接头组织由α相、少量β相、以及大量细小的再结晶α相构成.接头中母材、热影响区和焊缝的显微硬度值比较均匀,介于440~490HV之间.室温条件下,母材和接头的抗拉强度均高于1 000 MPa,延伸率均介于7%~10%;650 ℃拉伸,母材抗拉强度达到了750 MPa,延伸率最高达20%;接头的抗拉强度在700 MPa以下,延伸率在10%~14%之间.接头与母材的持久断裂均是由孔洞聚集形成微裂纹,在力的作用下不断扩展,直至最终断裂.而接头中柱状晶的晶界促进了裂纹的扩展,所以母材的持久寿命和应变优于接头.根据结果分别得出了650 ℃下接头和母材应力与寿命的关系式.     

800MPa级冷轧耐候双相钢连续冷却相变及组织性能研究

为了探索一种800 MPa级冷轧耐候双相钢的连续冷却转变规律及退火后组织性能变化,利用For-master-FⅡ全自动相变仪及连续退火模拟实验机,进行了连续冷却转变(CCT)曲线的测定及连续退火实验.结果表明:实验钢的过冷奥氏体在很低的冷却速度(0.5℃/s)下即可发生马氏体转变,而珠光体转变较少.当冷速为80℃/s时,仅发生马氏体转变;退火后实验钢显微组织中的马氏体呈带状分布,经最优工艺退火后实验钢的显微组织为多边形铁素体(79%)+块状马氏体(16%)+细小的残余奥氏体(5%),残余奥氏体主要分布于马氏体晶粒内部或铁素体的晶界处;实验钢屈服强度为387 MPa,抗拉强度为863 MPa,延伸率为18%,强塑积达到15534.     

Microstructure and mechanical properties of barium aluminosilicate glass-ceramic matrix composites reinforced with SiC whiskers

BAS glass-ceramic composites reinforced with different volume fractions (0, 10, 20, 30, 40 vol%) of SiC whiskers were successfully fabricated by a hot-pressing method. The microstructure, whisker/matrix interface structure, phase constitution and mechanical properties of the composites have been systematically studied by means of SEM, TEM, XRD techniques as well as three-point bending tests. It was demonstrated that the incorporation of SiC whiskers could significantly increase the flexural strength and fracture toughness of BAS glass-ceramic matrixes. The celsian seeds can effectively promote the hexacelsian-to-celsian transformation in BaAl₂Si₂O₈. The active Al₂O₃ added to the BAS matrix obviously reduced the amount of SiO₂ in the matrix and formed needle-like mullite. The high temperature strengths of the composites were also investigated.     

Mechanical and environmental factors in the cyclic and static fatigue of a machinable glass-ceramic

The effects of environment on cyclic and static fatigue behaviour were investigated with a machinable glass-ceramic and its original glass. Tests were conducted at ambient temperatures in three environments, i.e. moist air, distilled water and kerosene, and an indentation/bending technique was used. The results indicate that cyclic loading increases crack growth rates of glass-ceramic in all the three environments, but it just has a negligible effect on the original glass. The two materials were very sensitive to the amount of water in the test environment. For static fatigue of the glass-ceramic, both the slopes of da/dt-K_eff curves and their position along the abscissa varied with the environments, but under other conditions, only the position varied.     

Microstructure and mechanical properties of precipitation-hardened cast high-entropy superalloys

ABSTRACT

Recent studies indicated that precipitation-hardened high-entropy alloys (HEAs) possess outstanding properties. It is difficult to obtain substantial precipitated particles for HEAs at the as-cast condition. In this paper, cast precipitation-hardened high-entropy superalloys (HESAs) Ni_48?x Co₁₈Cr_10.5Fe_9.3Al_9.7Ti_4.5Mo _x (at.-%, x?=?1, 2, 3) were designed and prepared. All HESAs possess a high-entropy matrix and a fine γ′ particles structure. HESAs have higher ultimate tensile strength and elongation at room temperature than conventional Ni-based superalloys and close yield strength. All HESAs possess high compressive strength at elevated temperature. At 850?°C, the strengths of all alloys are higher than 800?MPa. Solid solution strengthening and precipitation strengthening were discussed. Precipitation strengthening has the greatest contribution to yield strength.     

受阻酚AO-80/NBR/PVC交联复合材料的结构与动态力学性能

在丁腈橡胶(NBR)/聚氯乙烯(PVC)共混基体中添加了受阻酚AO-80, 制备了AO-80/NBR/PVC交联复合材料, 并研究了其微观结构和动态力学性能。扫描电镜、 透射电镜的结果证明, 大部分AO-80溶解在NBR/PVC基体中, 少量的AO-80以亚微米尺寸的微粒分散于基体中; X射线衍射、 差示扫描量热分析(DSC)结果证明, AO-80在基体中处于非晶态。DSC、 动态热机械分析的结果表明, AO-80与基体之间形成了很强的分子间作用力, 使材料的玻璃化温度大幅度上升。同时, AO-80/NBR/PVC交联复合材料的损耗因子tanδ-温度T曲线只有一个单峰, 与纯的NBR/PVC交联橡胶相比, 随着AO-80用量增加, tanδ峰明显向高温移动, 并且峰值由0.96增加到1.56。AO-80/NBR/PVC交联复合材料呈现明显的拉伸取向, 具备优异的力学强度, 具有很好的实用价值。