Tensile and Fracture Properties of Cast and Forged Composite Synthesized by Addition of Al-Si Alloy to Magnesium

Cast Mg-Al-Si composites synthesized by addition of Al-Si alloy containing 10, 15, and 20 wt pct of Si, in molten magnesium, to generate particles of Mg₂Si by reaction between silicon and magnesium during stir casting has opened up the possibility to control the size of these particles. The microstructure of the cast composite consists of relatively dark polyhedral phase of Mg₂Si and bright phase of β-Al₁₂Mg₁₇ along the boundary between dendrites of α-Mg solid solution. After hot forging at 350 °C, the microstructure has changed to relatively smaller sizes of β-Al₁₂Mg₁₇ and Mg₂Si particles apart from larger grains surrounded by smaller grains due to dynamic recovery and recrystallization. Some of the Mg₂Si particles crack during forging. In both the cast and forged composite, the Brinell hardness increases rapidly with increasing volume fraction of Mg₂Si, but the hardness is higher in forged composites by about 100 BHN. Yield strength in cast composites improves over that of the cast alloy, but there is a marginal increase in yield strength with increasing Mg₂Si content. In forged composites, there is significant improvement in yield strength with increasing Mg₂Si particles and also over those observed in their cast counterpart. In cast composites, ultimate tensile strength (UTS) decreases with increasing Mg₂Si content possibly due to increased casting defects such as porosity and segregation, which increases with increasing Mg₂Si content and may counteract the strengthening effect of Mg₂Si content. However, in forged composite, UTS increases with increasing Mg₂Si content until 5.25 vol pct due to elimination of segregation and lowering of porosity, but at higher Mg₂Si content of 7 vol pct, UTS decreases, possibly due to extensive cracking of Mg₂Si particles. On forging, the ductility decreases in forged alloy and composites possibly due to the remaining strain and the forged microstructure. The initiation fracture toughness, J _IC , decreases drastically in cast composites from that of Mg-9 wt pct. alloy designated as MA alloy due to the presence Mg₂Si particles. Thereafter, J _IC does not appear to be very sensitive to the increasing presence of Mg₂Si particles. There is drastic reduction of J _IC on forging of the alloy, which was attributed to the remaining strain and forged microstructure, and it is further lowered in the composites because of cracking of Mg₂Si particles. The ratio of the tearing modulus to the elastic modulus in cast composites shows a lower ratio, which decreases with increasing Mg₂Si content. The ratio decreases comparatively more on forging of cast MA alloy than those observed in forged composites.     

Study of the Specifics of Liquid-Phase Oxidation of Aluminum Melt to Obtain an Aluminum Matrix Composite

Metallurgist - The paper describes theoretical studies and presents the results of practical experiments related to the production of aluminum matrix composites by internal oxidation. According to...     

高温合金表面激光熔铸镍基合金涂层的组织与耐磨性能

研究了高温合金ＧＨ３３表面激光熔铸镍基合金涂层的组织和耐磨性能。结果表明,基材对涂层合金的稀释作用较小;涂层与基材之间形成良好的冶金接合;涂层基体组织为γ－Ｎｉ枝晶,枝晶间为γ－Ｎｉ、Ｍ２３（ＣＢ）６、Ｎｉ３Ｂ、Ｃｒ２Ｂ、ＣｒＢ、ＷＣ等;涂层耐磨性能的平均值较基材提高４倍以上。     

Development of the Production Technology of Cast Aluminum Matrix Composite by Alumina Strengthening Phase Synthesis in an Aluminum Melt

Russian Journal of Non-Ferrous Metals - Currently, critical components and assemblies made of traditional materials do not always meet the increased requirements of designers and service...     

离心铸造自生初晶Si局部增强铝基复合材料活塞的组织与性能

离心铸造过共晶Al-18Si-4Mg合金,获得了自生初晶Si颗粒局部增强铝基复合材料活塞毛坯。检测了复合材料活塞的组织、硬度及耐磨性的分布规律。结果表明,在离心力的作用下,初晶Si颗粒偏聚于活塞的顶部和环槽区,而裙部为共晶组织;增强层具有较高的硬度和良好的耐磨性。     

铝合金/Q235钎剂涂层钢板异种金属CMT焊接分析

采用CMT(Cold Mental Transfer,冷金属过渡焊)焊接技术,分别对5083铝合金和6061铝合金与Q235钎剂涂层钢板进行焊接实验。采用NOCLOCK+30%Zn粉的钎剂配方和相同的焊接工艺参数,对焊缝界面组织的SEM和EDS观察分析,研究不同母材对铝合金/钢异种金属焊接的影响。结果表明:采用该钎剂配方可以基本满足铝合金/钢异种金属焊接的要求;铝母材中镁含量越高,得到的接头性能越差。     

等离子熔覆镍基合金及复合材料涂层的组织与性能研究

利用等离子表面熔覆工艺,在钢基表面获得了与基体呈冶金结合的镍基合金涂层、镍基+镍包碳化钨等涂层。利用光学电镜、扫描电镜以及能谱分析了上述涂层的组织及成分;采用维氏硬度计测定了涂层的维氏硬度;并比较了上述几种涂层的磨损性能。试验结果表明:等离子熔覆Ni基+30%镍包碳化钨的组织及性能优于其它涂层。     

铝合金表面磁屏蔽层的制备及性能

研究了在ZL102合金表面用等离子喷涂和有机树脂粘结法制备低频磁屏蔽防护层，对有机防护层与基体的结合力及各自的防护能力进行了测试。     

Improvement in the Environmental Resistance to Oxidation and Surface Properties of Simple Carbon Steel Using Aluminum Coating

In the present work, using a new approach, Fe?CAl intermetallics were formed on the surface of a low-carbon steel (ST52) in order to study its effects on the oxidation, hardness and abrasive behavior. The samples were welded with gas tungsten arc welding technique using an aluminum?Ciron powder (stoichiometry ratio of 1:1) as filer. The microstructural evolutions of coated samples were then characterized using scanning electron microscopy and X-ray diffraction techniques. Besides, hardness and abrasion tests were carried out to study the abrasive behavior of coated layer. The resistance to hot oxidation of coated samples were evaluated by heating to 500, 600 and 700?°C and holding for 2?h. The results show that Fe₃Al and aluminum?Ciron carbide (FeAlC_0.65) were formed on surface of samples. The formation of these phases resulted in increase in the hardness and oxidation resistance, while no improvement on the wear resistance was observed.     

熔体冷却速度对稀土Y变质A356铝合金微观组织及拉伸性能的影响

对不同熔体冷却速度所制备稀土Y变质A356铝合金的显微组织及拉伸性能进行了研究。结果表明,随着熔体冷却速度的降低,初晶α-Al晶粒变得粗大且分布凌乱,其二次枝晶间距增大;共晶硅由颗粒状、纤维状转变为片状、针状;合金的拉伸性能显著下降,拉伸断口由韧性断裂向脆性断裂转变。稀土Y对熔体冷却速度较敏感,需在较大的熔体冷却速度下才能使共晶硅按变质形态生长。     

SiC颗粒自增粘熔体发泡法制备泡沫铝铸锭的组织及其特征分析

通过SiC颗粒自增粘熔体发泡法工艺制备得到泡沫铝基材料的铸锭;对制得的泡沫铝铸锭进行各个层面上不同部位的平均孔径和平均孔隙率的测定,得到了铸锭内部的孔隙率和孔径在铸锭径向和高度方向上的变化规律;并且讨论和研究了熔体未发泡区域的形成原因,得到了熔体直接发泡法制备泡沫材料时气孔的形成过程模型。     

Al-5 Ti-1 B细化剂对7075铝合金组织与性能的影响

研究了Al-5 Ti-1 B细化剂对7075铝合金组织与性能的影响。结果表明：添加微量的Al-5 Ti-1 B细化剂可使7075铝合金的铸态组织从粗大的枝晶细化为细小均匀的等轴晶,随着Al-5 Ti-1 B细化剂添加量的逐渐增加,7075铝合金的晶粒平均直径逐渐减小,抗拉强度和伸长率逐渐提高。当添加0．3％的Al-5Ti-1B细化剂时,7075铝合金被细化为平均直径44．7μm的等轴晶,抗拉强度和伸长率分别提高至311 MPa和4．1％,与未添加Al-5 Ti-1 B细化剂相比,7075铝合金的晶粒平均直径下降了64．3％,抗拉强度和伸长率分别提高了13．1％和45．4％。     

提高铝合金强度的技术途径和方法

介绍了铝合金的强化的位错机制,论述了铝合金强化的技术途径和方法,并进一步研究了高强铝合金的发展趋势。     

Ti-5Al-2.5Sn合金粉末热等静压压坯的致密化行为及性能

粉末冶金近净成形工艺能够制备性能要求高、结构复杂的钛合金构件.将洁净Ti -5Al -2.5Sn预合金粉末封装在低碳钢材料制造的包套中,采用热等静压进行了粉体的致密化,研究了粉末在热等静压过程中的致密化行为.由于包套对热等静压压力的屏蔽效应,致密化过程后观察到了粉末/包套体的不均匀变形;通过有限元仿真也预测到包套对包套...     

逐步熔融凝固法工艺参数对金属基复合材料性能的影响

采用逐步熔融凝固法制备了WC-65Mn复合材料,用扫描电子显微镜观察试样的微观形貌和组织结构,并用IMAGETOOL软件分析不同试样的扫描图像,定量测定增强相WC颗粒的分布状况,同时测量材料的抗弯强度和硬度.研究证明电源功率和模具下降速率对增强相WC颗粒的分布状况和力学性能有重要的影响.电源功率应在5.5~7.5kW之间,模具下降速度为8~10mm/min.     

A Comparison of the Use of Ultrasonic Melt Treatment and Mechanical Vibration in the Manufacture of Al5Si5Zn Alloy Feedstock for Thixoforming

Metallurgical and Materials Transactions B - The use of physical agents when casting aluminum alloys has proven to be an effective route for grain refinement and avoids the inconvenience of...     

350kA大型预焙铝电解槽原铝质量波动的原因及对策

从原铝中杂质的构成和来源等方面作了分析，提出了控制原材料质量、改善优化电解槽原铝生产工艺技术参数和加强原铝质量考核等措施，取得了满意的效果。     

滴定法联合快速测定镍硼合金中的硼和铝

试样用过氧化钠熔融,用热水浸取熔融物,在乙醇存在下,加热煮沸驱除过氧化氢,定容后,过滤铁、镍、锰等沉淀与硼、铝分离,移取部分滤液分别测定硼、铝量。测定方法简便、快速,测定结果令人满意,硼的相对标准偏差≤0.74%,铝的相对标准偏差≤2.89%。     

NiCoCrAlY合金粉体形态及粒度分布对超音速等离子喷涂制备合金涂层氧化行为的影响研究

以不同粒度分布的四种NiCoCrAlY合金粉体为原料,采用最新开发出的高效能超音速等离子喷涂技术制备合金涂层。分别对合金涂层进行＂1000℃、8h预氧化＋1100℃、100h氧化＂及直接＂1100℃、120h＂高温氧化试验。对喷涂及氧化试验后的涂层进行SEM观察及EDX分析,结果表明：四种合金涂层在形成过程中,均发生了...