Y/Al-5Ti-1B复合变质对Al-7Si合金微观组织和力学性能的影响

在传统铸造Al-Si合金中存在的粗大树枝晶α-Al相以及针状共晶Si严重割裂基体,显著降低合金的力学性能。为细化Al-Si合金的组织,提升其力学性能,本文使用扫描电镜(SEM)、电子探针(EPMA)、X射线衍射仪(XRD)以及万能材料试验机,研究了不同添加量Y/Al-5Ti-1B变质剂(Al-5Ti-1B均为2%,稀土Y分别为0.05%、0.1%、0.2%、0.3%、0.4%、0.5%,质量分数)对Al-7Si合金微观组织和力学性能的影响,并探究了其对Al-7Si合金的变质机理。实验结果表明,当Al-5Ti-1B含量为2%、稀土Y含量为0.4%时,变质效果最佳,共晶Si由粗大针状变为细小颗粒状,长和宽分别减小至2.7和0.8μm,相较于未经变质处理的Al-7Si合金,减小了90.6%和4.7%。合金抗拉强度由原来的168.1 MPa提升至209.1 MPa,增加了24.4%。同时伸长率从6.23%提升至9.62%,增长了54.4%。此外,合金的断裂方式也从脆性断裂转变为韧-脆混合断裂。

Artificial Neural Network and Fuzzy Logic Based Techniques for Numerical Modeling and Prediction of Aluminum-5%Magnesium Alloy Doped with REM Neodymium

In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).

Investigation of the Laser Powder Bed Fusion Process of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy

Laser powder bed fusion(LPBF)is an advanced manufacturing technology;however,inappropriate LPBF process parameters may cause printing defects in materials.In the present work,the LPBF process of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy was investigated by a two-step optimization approach.Subsequently,heat transfer and liquid flow behaviors during LPBF were simulated by a well-tested phenomenological model,and the defect formation mechanisms in the as-fabricated alloy were discussed.The optimized process parameters for LPBF were detected as laser power changed from 195 W to 210 W,with scanning speed of 1250 mm/s.The LPBF process was divided into a laser irradiation stage,a spreading flow stage,and a solidification stage.The morphologies and defects of deposited tracks were affected by liquid flow behavior caused by rapid cooling rates.The findings of this research can provide valuable support for printing defect-free metal components.

Effect of addition of minor amounts of Sb and Gd on hot tearing susceptibility of Mg-5Al-3Ca alloy

The effects of addition of minor amount of(0.5 wt.%) antimony(Sb) or gadolinium(Gd) and combined addition of Sb and Gd(0.5 wt.%,respectively) on the hot tearing susceptibility(HTS) of Mg-5Al-3Ca alloy were investigated experimentally using a “T-shaped” hot tearing measuring system. Various solidification parameters of the alloys were measured and calculated through thermal analysis experiments. The microstructure, grain size, and morphology of the crack zone were characterized by scanning electron microscopy and electron backscatter diffraction, and the crystal phases of the alloys were analyzed by X-ray diffraction and energy-dispersive X-ray spectroscopy. The results showed that the addition of 0.5 wt.% Gd resulted in the increase in the vulnerable temperature range(Tv) and reduced the eutectic structure content that could participate in feeding, thereby improving the HTS of the alloy. However, addition of 0.5 wt.% Sb or combined addition of Gd and Sb(0.5 wt.%, respectively) to the Mg-5Al-3Ca alloy shortened the Tvand improved the skeleton strength of the alloy, thereby reducing HTS. Moreover, significantly refined structure of Mg-5Al-3Ca-0.5Gd-0.5Sb alloy improved the feeding ability of the eutectic structure, thus the alloy exhibited the lowest HTS.

Effect of Ti on microstructure and properties of electromagnetic stirred Al-18wt.%Mg_(2)Si alloy

By adding different amounts of Ti into the electromagnetic stirred Al-18wt.%Mg_(2)Si alloy,the effect of Ti element on the microstructure and mechanical properties of the alloy was studied.The experimental results show that the microstructure is refined after modification with Ti,which is related to the heterogeneous nucleation of TiAl_(3) particles on theα-Al matrix.With the increase of Ti content and holding time after stirring,the primary Mg_(2)Si phase is refined firstly and then coarsened,and correspondingly,the mechanical properties of the alloy show a trend of increasing at first and then decreasing.When the addition of Ti is 0.5wt.%and the holding time is about 20 min,the refinement effect of primary Mg_(2)Si phase is the most significant and the mechanical properties of the alloy are optimal.

Influence of elevated Fe,Ni and Cr levels on tensile properties of SSM-HPDC Al-Si-Mg alloy F357

The microstructures and tensile properties of semi-solid metal high pressure die cast(SSM-HPDC) F357 alloys with low and high levels of Fe,Ni and Cr were compared in different temper conditions.ThermoCalc software was used to predict the different intermetallics that can be expected in the alloys,and scanning electron microscopy(SEM) with energy dispersive spectroscopy(EDS) was used to investigate the actual intermetallics that formed.The influence of these intermetallics on tensile properties was quantified.The results show that lower strength is obtained in the alloy with high Fe,Ni and Cr levels.This is attributed mainly to the formation of more π-Al8FeMg3Si6 phase,which removes strengthening Mg atoms from solid solution.Also,the ductility of the high Fe,Ni and Cr levels alloy is decreased significantly due to microcracking of the higher volume fraction π-Al8FeMg3Si6 and Al9FeNi phases.The combination of lower strength and ductility results in a decrease of the quality index of this alloy compared with the alloy with low levels of Fe,Ni and Cr.

Efects of Al-Mn-Ti-P-Cu master alloy on microstructure and properties of Al-25Si alloy

To obtain a higher microstructural refining efficiency,and improve the properties and processing ability of hypereutectic Al-25Si alloy,a new environmentally friendly Al-20.6Mn-12Ti-0.9P-6.1Cu(by wt.%)master alloy was fabricated;and its modification and strengthening mechanisms on the Al-25Si alloy were studied.The mechanical properties of the unmodified,modified and heat treated alloys were investigated.Results show that the optimal addition amount of the Al-20.6Mn-12Ti-0.9P-6.1Cu master alloy is 4wt.%.In this case,primary Si and eutectic Si as well asα-Al phase were clearly refined,and this refining effect shows an excellent long residual action as it can be heat-retained for at least 5 h.After being T6 heat treated,the morphology of primary and eutectic Si in the Al-25Si alloys with the addition of 4wt.%Al-20.6Mn-12Ti-0.9P-6.1Cu alloy changes into particles and short rods.The average grain size of the primary and eutectic Si decreases from 250μm(unmodified)to 13.83μm and 35μm(unmodified)to 7μm;theα-Al becomes obviously finer and the distribution of Si phases tends to be uniform and dispersed.Meanwhile,the tensile properties are improved obviously;the tensile strengths at room temperature and 300 oC reach 241 MPa and127 MPa,increased by 153.7%and 67.1%,respectively.In addition,the tensile fracture mechanism changes from brittle fracture for the alloy without modification to ductile fracture after modification.Modifying the morphology of Si phase and strengthening the matrix can effectively block the initiation and propagation of cracks,thus improving the strength of the hypereutectic Al-25Si alloy.

Characteristics of Faigue Crack Initiation in Ti-5Al-4Sn-2Zr-1Mo-0.7Nd-0.25Si Alloy

The characteristics of fatigue crack initiation in Ti-5AI-4Sn-2Zr1Mo-O.7Nd-O.25Si alloy wereStudied. Two modes Of fatigue crack initiation were found. The Nd-rich phase particles displaybetter resistance to fatigue crack initiation than the matrix at lower stress.

Sb对原位Mg_2Si/Al-5Si复合材料显微组织的影响

研究了Sb含量对Mg2Si/Al-5Si复合材料显微组织的影响。结果表明,随着Sb含量的增加,初生Mg2Si颗粒形貌明显发生了细化,Mg2Si形态由变质前的汉字体和枝晶状变为细小的、均匀分布的颗粒状,Mg2Si体积分数也有所增加。当Sb含量为0·4%时,细化效果达到最佳,由变质前的52μm变为25μm。当Sb含量超过0·4%后,Mg2Si颗粒尺寸开始粗化,因此,过量的Sb对Mg2Si颗粒的细化无益。Sb对Mg2Si颗粒的细化主要由于AlSb引起的异质形核作用,Sb使液相线温度和熔体表面张力σLV降低,对Mg2Si颗粒的细化也具有一定的作用。

Al-5% Ti-1% B对Sr变质Al-13.0 %Si合金组织影响的研究

Sr作为变质剂加入到Al Si合金中能导致共晶硅的形态从粗大的片状 (或称为针状 )转变为细小的纤维状 ,但同时也促进了柱状枝晶的形成。当Al 5%Ti 1%B加入量低于 0 8%时 ,α枝晶有等轴化趋向 ,柱状枝晶的主干长度缩短 ,对共晶硅的形态与尺寸没有显著的影响 ,尽管共晶团尺寸略有下降。但当Al 5%Ti 1%B加入量超过 0 8%后 ,其对Sr变质作用的有害影响显现出来 ,α Al枝晶数量减少 ,出现初晶硅 ,共晶硅尺寸变大。随着加入量进一步增加 ,最终转变为未变质组织。所有的结果表明 :熔体中有效Sr量随着Al 5%Ti 1%B中间合金加入量的增加而降低 。

熔体超声波处理对Al-5%Si铸锭凝固组织的影响

为了研究超声波对金属熔体凝固过程中的影响,使用Al-5%Si合金进行了实验。在实验中采用几种不同的方法处理金属熔体:不添加除气剂、只添加除气剂、既添加除气剂又进行超声波处理。利用克劳修斯-克拉柏龙方程分析了超声波细化金属铸锭凝固组织的机理。结果表明,除气剂的添加与否对Al-5%Si合金铸锭组织的细化没有影响,铸锭由粗大的柱状晶组织构成;采用合适的超声波处理时间,Al-5%Si合金铸锭的等轴晶获得率大幅度提高,可使整个铸锭组织变为细化的等轴晶组织;超声波振动时间过长将导致铸锭内气孔的增加;根据克劳修斯-克拉柏龙方程,某一强度的超声波引起的压力冲击波作用,导致液相转变为固相,引起了超声波的细晶作用。

Al-5Ti-xCe细化剂制备及对Al-7Si合金组织和冲击性能的改善

试验研究了铈含量对细化剂Al-5Ti-x Ce(x分别为0.3,0.6,0.9)微观组织的影响,以及细化剂Al-5Ti-x Ce对Al-7Si合金组织和冲击性能的影响。结果表明,稀土Ce加入到Al-5Ti合金后,合金基体中的Al3Ti的尺寸明显降低,Al3Ti形状由长条状转变为羽毛状,并随着稀土Ce添加量增加,Al3Ti尺寸进一步降低,当Ce的加入量(质量分数,下同)为0.6%时,Al3Ti尺寸降低至最小,当Ce的添加量增至0.9%时,Al3Ti尺寸不再细化;用不同Ce的添加量的Al-5Ti-x Ce细化剂细化Al-7Si合金,发现随着Al-5Ti-x Ce中Ce的添加量增加,Al-7Si合金中α-Al树枝晶逐渐细化,其中Al-5Ti-0.6Ce细化剂的细化效果最佳;随着Al-5Ti-x Ce中Ce的添加量增加,Al-7Si合金中粗片状的共晶硅逐渐变得细小,其冲击性能随Al-5Ti-x Ce细化剂中铈含量的增加而显著提升,当Al-5Ti-x Ce中Ce的添加量增加到0.9%时,冲击性能不再增加。

离心转速对过共晶铝硅合金Al-19Si-5Mg组织的影响

通过改变离心铸造的转速,获得了内层聚集大量Mg2Si和初晶Si,中层不含Mg2Si和初晶Si,外层含有少量Mg2Si和初晶Si的Al-19%Si-5%Mg合金自生梯度功能复合材料圆筒形零件,分析了该复合材料零件组织分布特征和成型工艺过程及影响因素。实验结果表明:离心转速将明显影响第二相颗粒的分布;离心转速越高,颗粒的偏聚越明显。

高性能Al-5Mg-2Si-xCe合金的制备及其力学性能研究

以Al-5Mg-2Si合金为基体合金,通过掺杂稀土Ce元素对合金进行改性,制备了不同Ce掺量的Al-5Mg-2Si-xCe(x=0,0.2,0.4和0.6)合金。采用XRD、SEM、EDS和力学性能分析等方式,研究了合金的结构、微观形貌和力学性能。结果表明,Al-5Mg-2Si-xCe(x=0,0.2,0.4和0.6)合金主要由α相组合而成,掺杂Ce元素后出现了Al_(8)CeFe_(4)三元含铁相的化合物,说明Ce具有促进β-Fe相转化成α-Fe相Al_(8)CeFe_(4)的作用;不掺杂Ce元素的Al-5Mg-2Si合金的枝晶排列紊乱且尺寸较为粗大,掺入稀土Ce元素后,枝晶的排列得到了明显改善,并且随着Ce掺量的增加,晶粒逐渐细化,分布更为均匀,α-Al的尺寸也逐渐缩小;当Ce掺量为0.4%(质量分数)时,合金的抗拉强度和延伸率均达到最佳,分别为133.70 MPa和1.64%,相比Ce掺量为0时,分别增长了26.49%和115.79%;未掺杂Ce的合金主要为解离断裂,掺入Ce后,合金的断裂方式主要为延晶断裂,且断口处晶粒均较为完整未被拉裂。

稀土元素Ce对Sr变质的Al-5Si铝合金焊丝含氢量和焊缝气孔率的影响

通过减压凝固法、固态测氢法和X射线检测分别研究了稀土元素Ce对Sr变质的Al-5Si铝合金焊丝熔体吸氢倾向、焊丝合金含氢量和焊缝气孔率的影响。结果表明,单独添加0.02%(质量分数)的Sr时,Al-5Si合金焊丝含氢量和焊缝气孔率显著增加。当向含0.02%Sr的Al-5Si合金中添加0%~0.05%(质量分数)的Ce时,Al-5Si-0.02Sr-xCe合金焊丝含氢量随着Ce含量的增加而降低,并在Ce含量为0.05%时达到最低值0.07 mL/(100 g Al),较Al-5Si-0.02Sr合金焊丝降低了81.6%。进一步增加Ce的含量至0.1%,合金焊丝含氢量基本不变。随Ce含量的增加,焊缝的气孔率与合金焊丝含氢量的变化趋势基本一致,而且对于Ce含量大于等于0.05%的焊丝,其焊接形成的焊缝接头无气孔。Ce的添加对焊接接头的拉伸性能几乎没有影响,但是明显提高了焊接接头的弯曲性能。

Sr对Sb变质Mg-5Sn-1.5Al-1Zn-1Si合金组织的影响

用重力铸造法制备Sb及Sr＋Sb联合变质Mg-5Sn-1.5Al-1Zn-1Si合金,再进行不同的固溶处理,研究Sr对Sb变质Mg-5Sn-1.5Al-1Zn-1Si合金组织的影响。结果表明：Sb和Sr＋Sb联合变质均可以使初生Mg2Si和Mg2（Si,Sn）颗粒发生不同程度的球化,而Sr＋Sb联合变质比Sb单变质具有更好的细化和球化效果;Sr＋Sb联合变质后,共晶Mg2Si和Mg2（Si,Sn）相由汉字状变为细小近似球形或多边形颗粒状;Sb变质Mg-5Sn-1.5Al-1Zn-1Si合金在较低固溶温度和较短保温时间下即可使大部分Mg17Al12相和部分Mg2Sn相固溶到基体中,而Sr＋Sb联合变质合金组织中,Mg17Al12和Mg2Sn依然清晰可见,未完全溶解的Mg17Al12相发生球化,均匀的分散在基体中;Sr＋Sb联合变质Mg-5Sn-1.5Al-1Zn-1Si合金固溶温度要比Sb单变质时略高一些,但对固溶时间的影响并不明显。

除气剂和超声波对Al-5%Si铸锭除气的影响

研究除气剂和超声波对A l-5%S i合金铸锭除气的影响。分析不添加除气剂也不超声波处理、只添加除气剂不超声波处理、即添加除气剂又超声波处理情况下,铸锭的组织和除气效果。结果表明,采用合适的超声波振动处理,可显著地降低铸锭内的含气量。

Ce对Mg-14Al-5Si合金组织及性能的影响

针对耐热镁合金需求,以Mg-14Al-5Si合金为研究对象,向合金中加入Ce元素细化合金显微组织,从而提高合金力学性能。利用OM、SEM以及EDS对合金的显微组织及合金的成分进行观察分析,利用硬度计和万能电子试验机检测合金的布氏硬度及伸长率、抗拉强度、屈服强度。结果表明:Ce添加量为1.5%时,合金显微组织细化效果最佳,Mg2Si相平均尺寸由改性前的45.87μm变为6.07μm,粗大连续网格状的共晶β-Mg17Al12相也得到细化,甚至部分变为孤岛状分布。此时合金力学性能达到最佳,硬度为145 HB,抗拉强度为149 MPa,屈服强度为92 MPa,伸长率为3.91%。同时在Ce添加量为2%的合金中发现白色杆状的CeSi2化合物。

超声处理对Al-5Si合金除气效率的影响

考察了超声处理对Al-5Si合金除气效率的影响,对超声除气的机理进行了分析。研究发现,恰当的超声处理时间对合金有良好的除气效果;当超声处理时间为60〜120s时,铸锭的除气效果比较理想,密度和除气率最大值分别达到2.6613 g/cm^3和69.0%;同时,超声处理可使共晶Si颗粒变得分散和均匀;采用C2Cl6除气剂-超声联合处理可在短时间内达到良好除气效果,具有很高的除气效率。

Si元素对钛合金热稳定性影响研究

在不同温度下对3种不同Si含量的Ti-Si二元合金进行100h的热暴露实验,并通过力学性能表征其热稳定性,研究了Si元素对钛合金热稳定性的影响。结果表明,在实验条件下,Si元素的加入提高了合金的抗拉强度,Si含量越高,强度提升幅度越大;在热暴露过程中,当热暴露温度高于450℃时,Ti-Si合金的抗拉强度呈下降趋势,经500℃/100 h热暴露处理后表现出最差的热稳定性,其中Ti-0.4Si合金的伸长率降低至28.0%。Si元素扩散与偏聚形成的Ti_(5)Si_(3)是影响Ti-Si合金热稳定性的主要因素。