Ni-7Al-27Mo定向凝固共晶合金组织和性能的研究

作为高温使用的新型合金,Ni-A1-Mo定向凝固共晶合金以其优异的强度和组织稳定性而引起人们的极大兴趣。本文作者叙述了合金的显微组织、相体积百分数、相组成和aMo纤维相的尺寸和分布,研究了拉晶速度对合金的显微组织和拉伸强度的影响,研究了在1100℃经100h等温处理对合金显微组织和持久性能的影响。     

NiAl/Cr(Mo)-Hf 合金的高温变形行为

研究了铸造及热等静压 (HIP)处理后的两种NiAl/Cr(Mo) Hf合金的微观组织 ,分析发现合金主要由NiAl相和Cr(Mo)相以及铪固溶体和Heusler相组成。对合金的高温变形行为和断裂特征进行研究 ,结果表明该合金具有良好的高温压缩性能 ,并运用线性回归方法计算了应力指数n和变形激活能Q。     

Al-La过共晶合金的组织特征及力学性能

采用真空熔炼方法,在石墨铸型中制备了过共晶合金Al-30%La、Al-35%La和Al-40%La试样,研究了它们的组织形貌特征和力学性能,发现过共晶合金Al-30%La、Al-35%La和Al-40%La中的枝晶是不连续的,其中Al-35%La中的Al11La3是周期性双相枝晶。力学性能测试结果表明,过共晶合金Al-30%La、Al-35%La和Al-40%La的抗拉强度较低,但抗压强度较高,并具有一定的相对压缩率(7.06%~15.11%);由硬度测试结果可知,随La含量的增加,Al-La合金的硬度随之增大,但合金Al-35%La的硬度呈现出一个低谷。     

定向凝固LaB6-(Ti,Zr)B2共晶的组织与性能

采用激光区熔技术制备了La B6-(Ti,Zr) B2共晶复合材料,对共晶复合材料的微观组织形貌、力学性能和热电子发射性能进行了系统的研究。结果表明,通过区熔技术获得的复合材料增强相为全固溶体;随着凝固速率从V=8mm/h增加到V=200mm/h,(Ti,Zr) B2纤维非常规整、均匀的排列在La B6基体中,且纤维的直径和共晶间距逐渐减少、面密度逐渐增大。当V=200mm/h,La B6-(Ti,Zr) B2共晶复合材料的维氏硬度为18.4 GPa;断裂韧性呈现出各向异性,在垂直和平行纤维的方向上,断裂韧性值分别为4.5 MPa.m1/2和2.5 MPa.m1/2,垂直于纤维方向上复合材料优异的断裂韧性归因于裂纹的桥连机制;采用二极管原理对复合材料的热电子发射特性测试发现:当阳极温度从1400℃增大到1600℃时,最大电流密度分别为4.86 A/cm2、10.13 A/cm2、19.21A/cm2,对应的功函数分别为2.92 e V、2.76 e V、2.65 e V。     

探析熔体过热处理对亚共晶Al-Si合金凝固特性和组织的影响

文章将亚共晶Al-Si合金为研究对象,分析熔体过热处理对其凝固特性与组织的影响,在实验室配制Al-Si合金,对其进行熔体过热处理实验,分析不同实验条件下,Al-Si合金的凝固组织变化。     

循环热处理对定向凝固DZ417G高温合金组织和力学性能的影响

研究了镍基定向凝固高温合金DZ417G经多次循环热处理后的微观组织、力学性能和断裂方式的变化规律.随着循环热处理次数的增加,基体上较大的γ'强化相的数量降低,弥散的γ'相间距减小,合金室温硬度随之提高,900℃抗拉强度略微增大,拉伸塑性在3次循环热处理后有所下降.合金在980℃、216 MPa条件下的持久寿命随循环热处理次数的增加而延长,但循环热处理超过4次后,合金的持久寿命迅速下降.     

金锡共晶合金细小全层片结构凝固组织研究

采用成分微调和熔体温度过热处理手段研究了二者对金锡共晶合金凝固组织和加工性能的影响。研究表明:通过成分微调并结合适当熔体温度处理,可以消除合金凝固组织中的ζ’-Au5Sn初生相。在一定的过热温度范围内,适当提高熔体处理温度有利于共晶层片团的细化,获得了一种细小全层片结构(ζ’-Au5Sn+δ-AuSn)的共晶凝固组织,共晶层片间距约为0.07μm。在成分微调后并结合适宜的熔体温度处理,本工作得到的最佳共晶层片团平均尺寸约为4μm。可以预期这种细小全层片结构的金锡共晶合金凝固组织具有优异的加工性能。     

超音速气雾化过共晶Al-Si合金粉末特性及组织

利用超音速气雾化法制备过共晶Al-Si快凝合金粉末。对合金粉末形貌特征、组织结构及相组成进行研究,表明合金粉末细小均匀,组织主要颗粒状Si相和针状金属间化合物Al9FeSi3组成,而且尺寸比较细小,分布也较均匀。     

Al-Ni-Y三元合金定向凝固组织及高温压缩性能研究

本文选取96.5 at%Al-2.6 at%Ni-0.9 at%Y三元合金,进行下拉式定向凝固实验,研究同一温度梯度下,不同拉伸速率对凝固组织的影响,以及定向凝固后合金的高温压缩性能。实验结果表明:Al-Ni-Y三元合金定向凝固后获得了同一方向生长的组织。合金定向凝固后,高温压缩时峰值应力都遵循着一定的变化规律。     

强塑性变形对亚共晶Al-Mg_2Si合金组织及力学性能的影响

Al-Mg-Si合金中,Mg_2Si作为增强相往往以粗大的汉字状或骨骼状形态分布在晶界处,割裂了基体致使合金的强度和韧性都较差,所以为了提高合金材料的强度和韧性,需要改变Mg_2Si在基体中的大小、形貌、分布,使其尽量细小弥散分布在基体中,使合金的综合性能有更好的提高。本文针对一种高Mg_2Si含量的亚共晶Al-10.86Mg_2Si伪二元合金,在铸态合金中添加0.8%Sb元素以细化Mg_2Si共晶相,改善Mg_2Si增强相的分布,采用等通道转角挤压(ECAP)技术来细化Mg_2Si增强相和Al基体,制备出强度更高、韧性更佳、性能更好的Al-Mg-Si合金。     

Significant Improvement of Mechanical Properties in NiAl-Cr(Mo)/Hf Alloy by Suction Casting and Subsequent Hot Isostatic Pressing

The NiAl-28Cr-5.5Mo-0.5Hf eutectic alloy was prepared by the suction casting (SC) technique and subsequent hot isostatic pressing (HIP) treatment, and tested for compressive strength and fracture behavior in the temperature range of 300 to 1373 K. The microstructure of suction-cast alloy is characterized by fine interlamellar spacing, large area fraction of eutectic cell, and fine Heusler (Ni₂AlHf) phase distributed semicontinuously at the cell boundaries. After HIP treatment, Ni₂AlHf phase at the cell boundaries is transformed into Hf solid solution phase and distributed homogeneously within the NiAl matrix. Compared with the conventionally cast alloy, the room-temperature compressive strain and elevated temperature strength of suction-cast alloy are enhanced markedly after HIP treatment. The reason is that the HIP treatment causes Hf solid solution phase to distribute homogeneously and then strengthens the NiAl matrix.

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Effect of Pulsed Magnetic Field on Microstructure and Mechanical Properties of Eutectic Al-Si Alloy

Pulsed magnetic field (PMF) processing has been employed for refining the microstructure of eutectic (Al-12.4Si) Al-Si alloy in the current study. The effect of PMF on microstructure and mechanical properties of eutectic Al-Si alloy was studied. The results show that the morphology of primary α-Al was refined from coarse columnar dendrites to fine equiaxed dendrites by PMF treatment. Fine short rod-like or rounded particle-like eutectic silicon was formed during solidification of eutectic Al-Si alloy treated by PMF. PMF treatment reduced the size of eutectic silicon from 49 to 2.3 μm in length, and the width from 3.1 to 0.6 μm. The aspect ratio of eutectic silicon was also reduced by PMF treatment from slightly less than 16 to slightly less than 4. The ultimate tensile strength and elongation of eutectic Al-Si alloy with PMF treatment at room temperature were about 201 MPa and 8.8 pct, respectively, which were increased by 47 and 73 pct, respectively, compared with the eutectic Al-Si alloy without PMF treatment.     

定向凝固Fe-6.5%Si合金显微组织的EBSD分析

采用定向凝固方法制备了Fe-6.5%Si实验合金板,并进行了金相观察、X射线衍射分析,EBSD分析和磁性测定。结果表明,合金板由沿定向凝固方向（100）生长的粗大柱状晶所组成,柱状晶的平均截面直径约为3mm,柱状晶之间绝大部分为大角晶界,其余为少量小角晶界和重位点阵晶界。合金板具有强的立主织构并显示出优良的磁性能,其矫顽力只有3．45A／m,小于其他方法制备的Fe-6.5%Si合金。     

Influence of Growth Rate on Eutectic Spacing,Microhardness, and Ultimate Tensile Strength in the Directionally Solidified Al-Cu-Ni Eutectic Alloy

Metallurgical and Materials Transactions B - In this work, the mechanical properties of the Al-Cu-Ni eutectic alloy, Al-32.5 wt pct Cu-1 wt pct Ni, were investigated in terms of...     

Microstructure Formation and Mechanical Properties of AZ31 Magnesium Alloy Solidified with a Novel Mechanical Vibration Technique

A novel mechanical vibration for refining microstructure is reported where vibration energy was directly exerted into a molten alloy by a vibrating horn, and the vibrating horn was melted during vibration. Effects of vibration intensity and melt superheat on the microstructure and mechanical properties of AZ31 magnesium alloy were investigated. It is confirmed that the melting of the vibrating horn could effectively extract the superheat and latent heat from the interior of the molten alloy, leading to rapid cooling during the initial stage of solidification, and the cooling rate is strongly dependent on the vibration acceleration and melt superheat. This study showed that it was difficult to refine the solidified microstructure when the treated alloy was kept in the full liquid state within the entire vibrating duration. A significantly refined microstructure was obtained by applying mechanical vibration during the nucleation stage, and a globular microstructure could form in a few seconds after solidification. When the molten alloy was treated from 920 K to 903 K (647 °C to 630 °C), with increasing vibration acceleration from 2.5 to 19 m s^?2, the coarse dendritic microstructure of the produced AZ31 billets transformed into a well-refined, reasonably uniform, and non-dendritic one, and mechanical properties were improved significantly. Moreover, the mechanisms of microstructure formation are discussed.     

Effect of Ag Content on the Microstructure and Crystallization of Coupled Eutectic Growth in Directionally Solidified Al-Cu-Ag Alloys

A series of coupled eutectic growths along the univariant eutectic groove in the ternary Al-Cu-Ag alloy was studied to investigate the effect of Ag on the microstructure and crystallization of directionally solidified Al-Cu-Ag alloys. The results indicated that the eutectic morphology and orientation relationship (OR) between eutectic phases were modified as the Ag content in the Al-Cu-Ag alloys increased. At a lower growth velocity (R ≤ 1 μm/s), a banded structure formed and the interlamellar spacing decreased with the increasing Ag content. At a higher growth velocity (R ≥ 3 μm/s), the eutectic cell spacing decreased with increasing Ag content. Increasing the Ag content in the Al-Cu-Ag alloys enhanced the enrichment of the Ag solute in the liquid ahead of the quenched liquid/solid interface. In addition, increasing the Ag content in the Al-Cu-Ag alloys promoted the transformation from a “Beta 6” OR to an “Alpha 4” OR between eutectic phases. Modifications of the eutectic morphology and the OR during directional solidification were attributed to the enrichment of Ag content at the solid/liquid interface and the changes in the interfacial energy due to the increase in Ag solubility in the α-Al phase.