Influence of Process Parameters on Microstructure and Mechanical Properties of Friction-Stir-Processed Mg-Gd-Y-Zr Casting

Mg-10Gd-3Y-0.5Zr (wt pct) casting was subjected to friction stir processing (FSP) at a constant rotation rate of 800 rpm and varied travel speeds of 25, 50, and 100 mm/minute. FSP resulted in the generation of fine-grained microstructure and fundamental dissolution of coarse Mg₅(Gd,Y) phase at the grain boundaries, thereby enhancing the tensile properties significantly at both room and elevated temperatures. The grain size of the FSP samples decreased with the increasing travel speed, whereas the microstructure heterogeneity with the banded structure (onion rings) became evident at a higher travel speed. Tensile elongation of the FSP samples increased as the travel speed increased, whereas the highest strengths were obtained at the medium travel speed of 50 mm/minute. Higher strengths and greater elongations were observed for the FSP samples in the transverse direction (TD) than in the longitudinal direction (LD). After post-FSP aging, the strengths of the FSP samples were increased significantly with the TD and LD exhibiting the same strengths; however, the elongation was decreased remarkably with the TD having higher elongation than the LD. A variation of the tensile properties was discussed in detail based on the microstructure heterogeneity and fracture surfaces.     

Formation Mechanisms and Microstructure Characterization of Al/Al3Ni In-situ Composite by Compound Casting

Metallurgical and Materials Transactions B - The Compound casting method was used to produce an Al/Ni bimetal composite. The mechanisms of formation of the reinforcing intermetallic phases were...     

复合材料Al/Al4C3/Al2O3的组织结构与力学性能

采用机械合金化（ＭＡ）球磨和热压烧结工艺制备了复合材料Ａｌ／Ａｌ４Ｃ３／Ａｌ２Ｏ３，对其组织结构和力学性能进行了研究。结果表明，发育良好的Ａｌ４Ｃ３棒状单晶体和等轴状γＡｌ２Ｏ３均匀分布在铝晶界或晶粒内部，二者体积含量约为６６ｖ％。Ａｌ／Ａｌ４Ｃ３和Ａｌ／Ａｌ２Ｏ３界面洁净，为直接的原子结合，但不存在确定的位向关系。复合材料的室温、高温强度及刚度比粉末冶金纯铝（Ｐ／ＭＡｌ）显著提高。     

6101合金的显微组织特征及性能

通过对6101合金在不同热处理条件下的组织研究,总结分析在不同热处理条件下的合金显微组织特征,及其相应的拉伸性能指标。试验发现,该合金随着热处理温度的升高性能达到一个较高的值,随后随温度的升高合金性能缓慢下降,同时晶粒粗化比较明显,晶粒粗化对合金制品的性能影响较大。     

无压浸渗法制备SiCp/Al复合材料的微观组织与力学性能

采用无压浸渗方法制备了SiC颗粒增强铝基复合材料，研究了材料的微观组织和力学性能。结果表明，复合材料浸渗完全，SiC颗粒分布均匀，无偏聚现象。铸造态复合材料中存在界面反应，经过透射电镜观察和XRD分析确认该界面反应物为MgAl2O4。界面反应的存在提高了润湿性，促进了无压自发浸渗。高温热暴露处理可以提高复合材料的布氏硬度，热暴露处理后的界面反应物呈块状弥散分布，但是反应物的数量略有增加。     

逆相变退火对连铸坯组织和力学性能的影响

 研究了逆相变退火温度对0.1C5Mn钢连铸坯的组织结构和力学性能的影响规律,采用SEM进行组织结构的表征,利用XRD技术分析连铸坯退火后奥氏体含量,并测试了退火试样的力学拉伸性能。试验结果表明,连铸坯退火过程中发生奥氏体逆转变且在较低退火温度下有少量碳化物析出,随着退火温度升高,奥氏体含量先增加后减少,析出物逐渐溶解消失。提高退火温度可以显著提高试验钢的抗拉强度但却降低它的屈服强度,另外随退火温度升高,断后伸长率和强塑积先增高后降低。在625~650℃退火,可以获得20%~25%的伸长率。研究结果说明利用逆转变退火可以大幅度提高中锰钢铸坯的力学性能。     

Improving Microstructure and Mechanical Properties for Large-Diameter 7075 Aluminum Alloy Ingots by a Forced Convection Stirring Casting Process

Metallurgical and Materials Transactions B - A simple process so-called forced convection stirring casting (FCSC) was proposed to prepare large-diameter 7075 Al alloy ingots. The flow behavior,...     

Microstructure and Mechanical Properties of Ductile Cast Iron in Lost Foam Casting with Vibration

The microstructures and mechanical properties of the ductile cast iron （DI） specimens obtained by lost foam casting （LFC） with and without vibration were investigated. The results indicate that the number of the graphite nodule increases from 175 mm 2 of the specimens produced by LFC without vibration to 334 mm^-2 of the specimens produced by LFC with vibration, and the thickness of the ferrite shell increases. Meanwhile, the amount of the carbides decreases in the specimens produced by LFC with vibration and the granule structure then forms. These are mainly attributed to the ＂crystal shower＂ caused by the vibration. In addition, the tensile strength and elongation of DI specimens produced by LFC with vibration are improved due to the dispersion-strengthening of refined carbide and Dearlite colonv, uniform distribution of the graphite nodule, and increase of the amount of dimples and tearing edges.     

液态反应合成Mg-Li-MgO/Mg_2Si复合材料的组织与性能

用ＤＴＡ对ＳｉＯ２ 与ＭｇＬｉ 合金反应合成复合材料的热力学进行了研究, 证明反应能够进行。检测结果表明反应生成的粒子尺寸细小且分布均匀。复合材料的强度、硬度、弹性模量明显提高; 该复合材料的延伸率低于基体合金, 但仍可达到较高水平（ ＞ ４％） , 高于Ａｌ２Ｏ３ 及ＳｉＣ纤维增强复合材料。     

锆和钪对Al-Mg铸造合金组织和力学性能的影响

通过金相显微镜、拉伸力学性能测试、XRD等手段研究了在铸造Al-Mg合金中添加不同含量的钪和锆后合金的铸态组织。结果表明,合金添加钪和锆后,明显减小了枝晶网胞尺寸,细化了晶粒。当锆和钪的添加量分别为0.2%、0.4%时,铸造Al-Mg合金组织具有良好的综合性能。     

CrMnN(WC)抗磨蚀复合涂层的组织与性能

利用光学显微镜、透射电镜并通过磨蚀和拉伸试验研究了ＣｒＭｎＮ（ＷＣ）涂层的显微组织、微观结构与力学性能。结果表明：其显微组织为初晶微组织为初晶奥氏体和共晶体，其共晶体主要为奥氏体的Ｃ或Ｂ的体例物；涂层与基体的结合强度为４３６．７６ＭＰａ，涂层的磨蚀失重率为１１．１９ｍｇ／ｈ。     

高温合金GH150氩弧焊接头的组织和力学性能

用金相分析和微型剪切试验等方法研究了高温合金ＧＨ１５０焊接接头各区域的微观组织和力学性能分布特性。该焊接接头中的熔合区组织和力学不均匀性最为严重，是该焊接接头最薄弱的部位。     

Microstructure and Properties Analysis of Laser Welding and Laser Weld Bonding Mg to Al Joints

Laser welding and laser weld bonding (LWB) Mg to Al joints were obtained in different welding parameters. The penetrations and microstructures of these kinds of joints changed with the increasing of pulse laser power density. Both laser welding and LWB Mg to Al joints with the best properties were obtained in conductive welding mode. In laser welding Mg to Al joint, several intermetallics formed at the bottom of the fusion zone, where some cracks were generated. In laser weld bonding Mg to Al joint, the decomposition of the adhesive caused a baffle effect on the diffusion between the Mg and the Al. The intermetallics formed in the middle of the fusion zone, and the thickness of Mg₁₇Al₁₂ layer was approximately 10 to 20 μm and the Mg₂Al₃ layer was less than 5 μm, which influenced the property of the joint less.     

Microstructure and Mechanical Properties of Modified M2 High-Speed Steel by Adding La2O3 in the Electroslag Casting Process

An electroslag casting method is used to add rare-earth La to M2 high-speed steels by adding La₂O₃ into the molten slag. The effects of the La content on the microstructure and mechanical properties of M2 high-speed steel are studied. The results show that rare-earth La is effectively added to steel by taking advantage of the decomposition of La₂O₃. The rare-earth La partially modifies the pre-existing oxide and sulfide inclusions into small and spherical rare-earth oxysulfide inclusions. By adding an appropriate amount of La, the as-cast iron dendrite matrix and coarse eutectic carbides can be refined, the carbide content is reduced, the carbide network is broken, and the decomposition of M₂C into M₆C and MC is promoted. After heat treatment, the network breaking and spheroidalization of the carbides are further facilitated, and the carbide content is reduced. The impact toughness and bending strength of the studied samples are improved by modifying the inclusions and optimizing the microstructure.     

Effect of Rare Earths on Mechanical Properties and Microstructure of TiCN/Al2O3 Ceramics

The effects of Y on mechanical properties and microstructure of TiCN/Al2O3 ceramics were studied in details. The experimental results show that the mechanical properties and microstructure can be improved by adding rare earth in TiCN/Al2 O3 ceramics, flexural strength and fracture toughness of the composites increased when Y is doped by 18.99% and 18.58% than those of the matrix, respectively. Microstructure of cracks extension was observed through SEM and TEM. The mechanics of particles bridge, cracks branch and cracks deflection are enforced obviously during the processes of cracks extension because strong interfaces and weak interfaces coexist, so manifold mechanics of enforcement of toughness act upon together to increase fracture toughness of TiCN/Al2 O3 doped with Y.