高铁含量挤压铸造铝铜合金中富铁相演变及对拉伸断裂行为的影响

采用拉伸性能测试、扫描电镜、透射电镜、深腐蚀、定量金相等技术手段研究了不同Fe含量的挤压铸造铝铜合金中富铁相演变规律及对合金拉伸断裂行为的影响。结果表明:随着Fe含量的增大,合金力学性能急剧下降,这主要是由于针状富铁相逐渐增多,富铁相体积分数的增多及尺寸的增大,同时铝基体里面的强化相减少。汉字状的α-Fe和Al6(Fe Mn)对高铁含量的合金性能危害性不大,这主要是由于汉字状的α-Fe和Al6(Fe Mn)中的枝晶臂与铝基体的界面结合能力更强,同时阻碍拉伸过程中裂纹扩展。而粗大针片状的β-Fe和Al3(Fe Mn)在拉伸过程中容易导致应力集中,成为裂纹的起源,同时在合金凝固过程中阻碍补缩通道形成铸造缺陷,从而恶化合金力学性能。挤压压力可以减少针状富铁相,并使针状富铁相高径比增大,同时细化富铁相尺寸。所有这些因素都能够减少富铁相本身开裂的趋势,同时增大富铁相与铝基体界面的结合力,从而提升合金力学性能。     

挤压铸造Al-5.0Cu-0.6Mn-0.5Fe合金的显微组织和力学性能

采用拉伸性能测试、定量金相分析、扫描电镜等手段研究挤压铸造Al-5.0Cu-0.6Mn-0.5Fe合金的显微组织和力学性能,分析挤压压力对合金的力学性能和显微组织的影响。结果表明:当挤压压力从0增大到75 MPa时,合金的抗拉强度(σb)和伸长率(δ)都显著增加。当挤压压力为75 MPa时,铸态合金的抗拉强度为298 MPa,伸长率达17.6%;经T5热处理后,合金的抗拉强度为395 MPa,伸长率为14.2%。当挤压压力从0增大到75 MPa时,α(Al)二次枝晶间距减小了69%,θ相(Al2Cu)和富Fe相的体积分数略有降低,针状β-Fe相消失,同时晶界处汉字状α-Fe相由连续的汉字状变成分散、细小的骨骼状。     

Mn、Fe质量比对挤压铸造Al-Cu合金组织与性能的影响

研究了不同Mn、Fe质量比和挤压压力对Al-Cu合金显微组织与力学性能的影响,并分析了其作用机理。结果表明,不同w(Mn)/w(Fe)的Al-Cu合金中主要存在4种富Fe第二相,即鱼骨状AlmFe、块状ɑ-Fe和Alm(FeMn)相以及针状β-Fe相;挤压压力为70 MPa时,合金中富Fe相相较于压力为0时更加细小和分散,且合金中针状β-Fe相在w(Mn)/w(Fe)为0.8时基本消失;而挤压压力为0,w(Mn)/w(Fe)为1.6时才基本消失;随着合金中w(Mn)/w(Fe)和挤压压力的增加,富Fe相圆整度提高,但是并不能显著改变合金中鱼骨状富Fe相的尺寸;挤压压力为0,Al-Cu合金在w(Mn)/w(Fe)为1.6时取得力学性能最佳值,而挤压压力为70 MPa时合金的最佳力学性能出现在w(Mn)/w(Fe)为1.2时。     

Si含量对挤压铸造Al-5.0Cu-0.6Mn-0.7Fe合金显微组织和力学性能的影响

采用拉伸性能和硬度测试、光学显微镜、扫描电镜和X射线衍射仪等手段研究不同Si含量对挤压铸造Al-5.0Cu-0.6Mn-0.7Fe合金显微组织和力学性能的影响。结果表明:当挤压压力为0时,随着Si含量的增加,凝固后期形成的富铁相阻止液相补缩,形成缩松组织,导致合金的抗拉强度、屈服强度和伸长率都下降;当挤压压力为75MPa时,随着Si含量增加,缩松组织消失,虽然细小和分散的α-Al15(Fe Mn)3(Si Cu)2相和Al2Cu相数量增多,但Al6(Fe Mn Cu)相消失,有利于晶界强化和阻止裂纹的扩展,使得合金的抗拉强度和屈服强度增加;虽然富铁相数量的增加使得合金伸长率降低,但挤压铸造工艺减缓了伸长率降低的趋势。当挤压压力为75 MPa和Si含量为1.1%(质量分数)时,合金的综合力学性能最好,其抗拉强度为232 MPa,屈服强度为118 MPa,伸长率为12.4%。     

挤压铸造对过共晶Al-Si-Cu-Mg合金组织与性能的影响

研究了比压对挤压铸造Al-17.5Si-4Cu-0.5Mg-0.1Mn合金的显微组织和力学性能的影响规律。结果表明,在压力下凝固时,合金的显微组织发生明显改善,力学性能大幅提高。且在一定压力范围内,随着挤压力的增加,α(Al)枝晶明显细化,枝晶间距减小,共晶Si相、Al2Cu相等强化相尺寸减小,力学性能提高;但当挤压铸造比压达到850 MPa时,合金的硬度和强度反而略有下降。与此同时,合金的伸长率却随着挤压铸造比压的增大持续升高。因此,比压为670 MPa时,挤压铸造Al-17.5Si-4Cu-0.5Mg-0.1Mn合金获得较好的组织与性能。     

挤压铸造Al-5.0Cu-0.8Mg-0.5Fe合金的组织及性能

采用金相组织观察、扫描电镜、拉伸性能测试等手段,研究了挤压铸造Al-5.0Cu-0.8Mg-0.5Fe合金的组织演变和力学性能。结果表明,当挤压压力从0增大到75 MPa时,合金的力学性能得到显著提高,这主要是由于挤压压力有利于Al-Cu合金中汉字状AlmFe相的形成,抑制针状β-Fe相的形成,同时显著细化富Fe相,减少铸造缺陷。当挤压压力为75MPa时,铸态下合金抗拉强度为258 MPa,伸长率为8.5%,经T6热处理后,其抗拉强度为432 MPa,伸长率为6.7%。     

Fe含量对挤压铸造Al-3.5Mg-0.8Mn合金组织性能的影响

采用拉伸和硬度测试、扫描电镜和X射线衍射仪等手段,研究了不同Fe含量对挤压铸造Al-3.5Mg-0.8Mn合金显微组织和力学性能的影响。结果表明,Fe能改善合金的力学性能,合金中只存在Al₆(FeMn)相。合金的抗拉强度和屈服强度随着Fe含量的增加而增大,伸长率随着Fe含量的增加而降低,原因是随着Fe含量增加,硬脆的Al₆(FeMn)相增多。在挤压压力为75MPa和Fe含量为0.5%时,合金的综合力学性能最佳,其抗拉强度为252MPa,屈服强度为128MPa,伸长率为28%。     

再生铸造Al-Cu合金中富Fe相形态及控制研究现状

Fe是铝合金中的有害杂质元素,废铝再生时Fe将不断累积,控制富Fe相的危害是促进废铝回收和高效利用的关键环节。综述了铸造Al-Cu合金中富Fe相的研究现状,包括富Fe相的类型以及富Fe相的控制方法。结果表明,在AlCu合金中富Fe相的形貌与种类取决于不同的合金成分以及铸造工艺条件,其存在形式主要是针状β-Fe,Al3(FeMn)以及汉字状的α-Fe、AlmFe、Al6(FeMn)相。针状β-Fe被认为是热处理过程中最稳定的富Fe相,其他富Fe相将在热处理过程中发生固态相变,最终转变成β-Fe。改变富Fe相形态是控制富Fe相的有效方式,主要方法包括中和变质、改变熔铸工艺和施加外场作用,但是无法从根本上解决富Fe相增多对铝合金的危害。开发更加有效的中和变质剂或者高效、经济的除Fe技术是未来的发展方向。铸造Al-Cu合金中富Fe相的研究主要集中于重力铸造条件下的,而对于超声波、压力等特种条件下富Fe相的研究将受到重视。     

RE对挤压铸造AlSi7Cu4MgMn合金组织和性能的影响

研究了不同RE(Ce、La混合稀土)含量对挤压铸造AlSi7Cu4MgMn合金组织、力学性能及铸造性能的影响。结果表明,RE可提升合金铸造性能,大幅度提高合金成形的良品率。不含RE时,AlSi7Cu4MgMn合金微观组织由α-Al基体、共晶Si相、块状α-Fe相、小块聚集状Al_2Cu相及其他强化相组成;添加适量RE后,块状Fe相转变为短棒状形态,Al_2Cu相细化并形成Al_xCu_4Mg_5Si_4复杂相;过量RE添加会导致合金中富Fe相聚集长大,恶化合金性能。添加0.25%的RE时合金力学性能最佳,抗拉强度为430MPa,屈服强度为392MPa,伸长率为6.8%。     

高压和锰添加对流变挤压成形过共晶Al-Si合金富铁相和力学性能的影响（英文）

研究高压和锰添加对流变挤压成形Al-14Si-2Fe合金富铁相和力学性能的影响。首先,将半固态合金熔体进行超声振动处理,然后挤压成形。结果显示,当挤压力为0 MPa时,无超声挤压成形的Al-14Si-2Fe-(0.4,0.8)Mn合金铸态组织中的富铁相主要由粗大β-Al_5(Fe,Mn)Si相、δ-Al_4(Fe,Mn)_3Si_2相和骨骼状α-Al_(15)(Fe,Mn)3Si_2相组成。在流变挤压成形下,富铁相首先被超声振动细化,然后压力下的凝固使其尺寸进一步减小。在α相的形成过程中发生包晶反应。当合金成分相同时,流变挤压成形试样比无超声挤压成形试样的抗拉强度高;当成形工艺相同时,Al-14Si-2Fe-0.8Mn合金比Al-14Si-2Fe-0.4Mn合金的抗拉强度高。     

Influence of high pressure and manganese addition on Fe-rich phases and mechanical properties of hypereutectic Al−Si alloy with rheo-squeeze casting

The influence of high pressure and manganese addition on Fe-rich phases (FRPs) and mechanical properties of Al?14Si?2Fe alloy with rheo-squeeze casting (RSC) was investigated. The semi-solid alloy melt was treated by ultrasonic vibration (UV) firstly, and then formed by squeeze casting (SC). Results show that the FRPs in as-cast SC alloys are composed of coarse β-Al₅(Fe, Mn)Si, δ-Al₄(Fe, Mn)Si₂ and bone-shaped α-Al₁₅(Fe, Mn)₃Si₂ phases when the pressure is 0 MPa. With RSC process, the FRPs are first refined by UV, and then the solidification under pressure further causes the grains to become smaller. The peritectic transformation occurs during the formation of α phase. For the alloy with the same composition, the ultimate tensile strength (UTS) of RSC sample is higher than that of the SC sample. With the same forming process, the UTS of Al?14Si?2Fe?0.8Mn alloy is higher than that of Al?14Si?2Fe?0.4Mn alloy.     

Effect of Mn on Fe containing phase formation in high purity aluminium

In this study, the effect of varying Mn additions on Fe phase formation in high purity Al and its corresponding effect on the resulting mechanical properties have been investigated. Thermodynamic simulations have shown that in the Al–Fe–Mn ternary system two intermetallic phases (namely Al₆(Fe,Mn) and Al₁₃Fe₄) form. Findings indicated that a relatively high amount (>1 wt-%) of Mn was required to achieve Al₆(FeMn) phase formation which was congruent with experimental results. Both the Al–Fe and Al–Fe–Mn phases observed displayed fibre/platelet type morphologies and were found to exist at α-Al grain/cell boundaries. Results indicate that the Fe phases coarsen with increasing Mn content. In the Al–Fe system the Mn addition improves yield strength (YS) and ultimate tensile strength (UTS) but reduces elongation beyond the reduction resulting from the Fe addition. The further decrease in elongation with Mn was attributed to the increase in volume fraction of the intermetallic phases.     

Effects of ultrasonic vibration and manganese on microstructure and mechanical properties of hypereutectic Al–Si alloys with 2%Fe

The effects of ultrasonic vibration (USV) on the microstructure and mechanical properties of Al–17Si–2Fe–2Cu–1Ni (mass %) alloys with 0.4% or 0.8% Mn were studied. The results show that the average grain size of primary Si in the alloys treated by USV could be refined to 21–24 μm, whether with or without P modification. The P addition has no further refinement effect on the primary Si in the case of the combined use of USV with P addition. Without USV, the alloy with 0.4%Mn contains a large amount of long needle-like β-Al₅(Fe,Mn)Si phase and coarse plate-like δ-Al₄(Fe,Mn)Si₂ phase. Besides, the alloy with 0.8% Mn contains a small amount of coarse dendritic α-Al₁₅(Fe,Mn)₃Si₂ phase. With USV treatment, the Fe-containing compounds in the alloys are refined and exist mainly as δ-Al₄(Fe,Mn)Si₂ particles with average grain size of about 18 μm, and only a small amount of β-Al₅(Fe,Mn)Si phase is remained. With USV treatment and without P modification, the ultimate tensile strengths (UTS) of the alloys containing 0.4% and 0.8% Mn are 271 MPa and 289 MPa respectively at room temperature, and the UTS are 127 MPa and 132 MPa at 350 °C. The Brinell hardness of the alloys are 131 HB and 139 HB respectively. It is considered that the modified morphology and uniform distribution of the Fe-containing intermetallic compounds and the primary Si phases, which are caused by USV process, are the main reasons for the increase of the tensile strength and hardness of these two alloys.     

Bulk amorphous FC20 (Fe–C–Si) alloys with small amounts of B and their crystallized structure and mechanical properties

The addition of a small amount (0.4 mass%) of B to a commercial FC20 cast iron was found to cause the formation of an amorphous phase in melt-spun ribbon and cast cylinders with a diameter of up to 0.5 mm. The structure of a melt-spun B-free FC20 alloy consisted of α-Fe, γ-Fe and Fe₃C. The effectiveness of additional B is presumably due to the generation of attractive bonding nature among the constituent elements. The amorphous alloy ribbon exhibits a high tensile strength of 3480 MPa and good bending ductility. The annealing causes the formation of an amorphous phase containing α-Fe particles with a size of about 30 nm. The mixed phase alloy exhibits an improved tensile strength of 3800 MPa without detriment to good ductility. With further increasing temperature, the mixed amorphous and α-Fe structure changes to α-Fe+Fe₃C+graphite through the metastable structure of α-Fe+Fe₃C. The structure after annealing for 900 s at 1200 K has fine grain sizes of about 0.5 μm for α-Fe, 0.3 μm for Fe₃C and 1 μm for graphite. The graphite-containing alloy exhibits high tensile strength of 1200–2000 MPa and large elongation of 5–13%. The high tensile strength and good ductility were also obtained for the 0.5 mm cylinder annealed at 1200 K. The good mechanical properties are due to the combination of fine subdivision of crack initiation sites by the homogeneous dispersion of small graphite particles and the dispersion strengthening of Fe₃C particles against the deformation of the α-Fe phase. The synthesis of the finely mixed α-Fe+Fe₃C+graphite alloys having good mechanical properties by crystallization of the new amorphous alloy in the melt-spun ribbon and cast cylinder forms is encouraging for the future development of a new Fe-based high-strength and high-ductility material.     

The Effect of Alloying Elements on the Microstructure of Al-5Fe Alloys

The effects of adding Cr, Mn, and Zr on the microstructure of Al-5Fe alloys has been studied by metallographic analysis, scanning electron microscopy, x-ray diffraction analysis, and differential thermal analysis. It has been found that the effects of the different elements on the microstructure of ferro-aluminum intermetallics in Al-5Fe alloys are not alike. Addition of Cr in Al-5Fe alloys dissolves only into AlFe intermetallics, resulting in the morphology of the AlFe phases being changed with increasing Cr content. Cr is a favorable nucleating agent for encouraging metastable Al _x Fe (x = 4.6 to 5.0) phase formation. Adding Mn in Al-5Fe alloys may stabilize the metastable Al₆Fe phase, helping the primary phase field of Al₇Cr diminish or even disappear and forcing Cr to dissolve into AlFe phases. Adding Zr does not refine the primary AlFe intermetallics. Al₃Zr particles in Al-5Fe alloys will occupy the growing spaces of ferro-aluminum phases and indirectly hinder the growth of Fe-bearing phases.     

Design of ultrafine eutectic-dendrite composites with enhanced mechanical properties in Fe-based alloy

The effect of Mn content on the evolution of microstructure and the enhancement of mechanical properties in Fe-Nb-Mn hierarchical composites consisted of ultrafine eutectic and primary dendrite has been studied by using X-ray diffractometry, scanning electron microscopy, transmission electron microcopy and compression test. Fe-11Nb-5Mn hierarchical composite consisted of α′-Fe dendrite and urtrafine α′-Fe + Fe₂Nb eutectic, and exhibited a reasonably good combination of mechanical properties, i.e. yield strength of 1283 ± 10 MPa and compressive plastic strain of 7.75 ± 5%, while Fe-11Nb-15Mn composite consisted of ?-Fe dendrite and ?-Fe + Fe₂Nb eutectic structure with some retained γ phase, and exhibited a far better combination of mechanical properties, i.e. higher yield strength of 1462 ± 10 MPa and larger compressive plastic strain of 11.28 ± 2%. The origin for the simultaneous enhancement of high strength and large plastic strain is attributed to ?-Fe martensite formation and strain-induced martensitic transformation from ? to α′ during deformation.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> particles on the microstructure and sliding wear of 7075 Al alloy manufactured by squeeze casting method

Aluminum (Al) alloy 7075 reinforced with Al₂O₃ particles was prepared using the stir casting method. The microstructure of the cast composites showed some degree of porosity and sites of Al₂O₃ particle clustering, especially at high-volume fractions of Al₂O₃ particles. Different squeeze pressures (25 and 50 MPa) were applied to the cast composite during solidification to reduce porosity and particle clusters. Microstructure examinations of the squeeze cast composites showed remarkable grain refining compared with that of the matrix alloy. As the volume fraction of particles and applied squeeze pressure increased, the hardness linearly increased. This increase was related to the modified structure and the decrease in the porosity. The effect of particle volume fraction and squeeze pressure on the dry-sliding wear of the composites was studied. Experiments were performed at 10, 30, and 50 N with a sliding speed of 1 m/s using a pin-on-ring apparatus. Increasing the particle volume fraction and squeeze pressure improved the wear resistance of the composite compared with that of the monolithic alloy, because the Al₂O₃ particles acted as load-bearing constituents. Also, these results can be attributed to the fact that the application of squeeze pressure during solidification led to a reduction in the porosity, and an increase in the solidification rate, leading to a finer structure. Moreover, the application of squeeze pressure improved the interface strength between the matrix and Al₂O₃ particles by elimination of the porosity at the interface, thereby providing better mechanical locking.     

A eutectoid phase transformation for the primary intermetallic particle from Alm(Fe,Mn) to Al3(Fe,Mn) in AA5182 alloy

The size and morphology evolution of the primary intermetallic particles in a DC-cast AA5182 alloy during homogenization at 470 and 520 °C has been studied. A eutectoid phase transformation of the primary particles Al_m(Fe,Mn) → Al₃(Fe,Mn) + Al is observed by field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). After the transformation, Al_m(Fe,Mn) particles become a lamellar mixture of Al₃(Fe,Mn) and Al, which is believed to be beneficial to the break-up of the large primary particles during hot rolling. The transformation mechanism and the transformation kinetics have been studied. During isothermal treatment at 520 °C, the fractional transformation rate is mainly controlled by nucleation. At 470 °C, the phase transformation is controlled by both nucleation and growth of Al₃(Fe,Mn) in Al_m(Fe,Mn) phase.