Ca对共晶Al-Si合金磷变质效果的影响

利用金相和电子探针微量分析仪(EPMA)等手段研究了共晶Al-Si(ZL109)合金熔体中Ca对Al-Si合金变质效果的影响.结果表明:合金中的Ca能使P变质失效,甚至出现类似Na变质处理的效果.分析表明:Ca能与合金熔体中的P形成比AIP更稳定的CaxPy化合物,从而抑制了P变质作用的发挥;C2Cl6精炼可使CaxPy化合物分解,重新形成AlP,从而使P变质效果得以恢复.     

钠盐与Al-10Sr在Al-Si合金复合变质处理中的交互作用

通过钠盐与Al-10Sr中间合金两种变质剂的复合添加,研究了Na与Sr对Al-Si合金的复合变质,以及两种变质剂之间的相互影响。结果表明,Na和Sr在合金中同时存在对共晶硅具有协同变质作用;但是钠盐与Al-10Sr中间合金两种变质剂的复合使用会导致Na和Sr的吸收率发生变化,其中钠盐的存在会导致Sr的含量和吸收率大幅下降,而Sr的存在促进了Na的吸收,分析认为这是由于钠盐与Sr发生了反应而导致的。合金中Na与Sr的含量共同决定了变质效果,对于含Si为9%的Al-Si系合金,用10×10~(-4)%~12×10~(-4)%Na与48×10~(-4)%~87×10~(-4)%Sr复合添加使用能够获得较好的变质效果。     

冷却速率和锶加入量与共晶硅变质等级相关性

通过光学显微镜和扫描电镜考察了冷却速率及Sr加入量对亚共晶Al-Si合金中共晶Si形貌变化的影响.Boltzman方程对共晶Si变质等级关系曲线拟合结果表明:随着冷却速率提高,共晶Si完全变质所需要的临界Sr量减少,共晶Si的变质等级与Sr的加入量高度相关,相关系数R2大于0.99.可以推断,在正常铸造条件下,存在变质...     

细化变质对亚共晶Al-Si合金熔体结构的影响

在分析二元亚共晶Al-Si合金熔体结构,以及Al、Si、Ti、Sr等主要组元物性特点的基础上,利用电子理论论述了细化和变质对亚共晶Al-Si合金熔体结构的影响。细化和变质过程可归结为活性元素Ti、Sr分别与熔剂Al原子和溶质Si原子之间的电子交换,从不同角度提高了熔体结构的均匀性,不仅改善合金熔体结构,而且相互抑制衰退。     

锶变质铝硅合金吸氢问题的研究及其精炼方法

Al-Si合金的加Sr变质工艺已从实验室进入实际生产应用,但增氢问题是Sr变质的主要缺点。本文探讨了Sr变质Al-Si合金增氢的原因,发现这些氢不是由于变质处理过程中Al-Sr中间合金与大气中水汽反应而产生的,而是Al-Sr中间合金本身含有大量的氢。质谱分析结果表明,Al-Sr中间合金中存有SrH化合物。各种精炼方法的比较试验表明,对Sr变质处理后的ZL102合金用多孔吹头通工业氩气精炼,除氢效果明显,对变质有效期影响较小,是一种较理想的精炼方法。     

直流电处理对加Sr变质的Al-Si合金显微结构的影响

对加Sr变质的Al-Si合金熔体进行了直流电处理,用扫描和透射电镜研究了加Sr变质与直流电熔体处理对共晶硅生长形态的影响。结果表明,加Sr变质的共晶硅呈条状或纤维状,经直流电熔体处理后,共晶硅变为圆球状,其颗粒尺寸在0.02～0.25μm范围内。     

Mg对共晶Al-Si合金磷变质效果的影响

研究结果表明,经过磷变质处理的共晶Al-Si合金中加入1.2%的Mg后,磷变质效果变差,甚至出现类似钠变质处理的特征.分析认为:Mg能与合金熔体中P形成比AlP更稳定的化合物,抑制了磷变质作用的发挥;在加入Mg再进行变质处理的情况下,变质效果良好.     

Al-Si合金共晶形核与生长机制研究

Al-Si二元共晶反应发生在凝固后期,共晶(团)晶粒的形核、生长都直接影响缩松、热裂等缺陷的形成、杂质元素及化合物的分布等。对Al Si10.5亚共晶合金进行Sr变质,对未变质与变质合金进行微观组织观察和EBSD分析,并对未变质合金进行热分析。结果表明:无论变质与否,共晶在初生枝晶上形核和在枝晶间异质上形核的这两种情况都存在,并且Sr对初生α-Al有明显的变质效果,富Fe相可能对共晶Si相形核有较大影响。     

Sr/P变质处理对挤压铸造Al-17.5Si合金组织与性能的影响

研究Sr和P变质对挤压铸造Al-17.5Si合金组织与力学性能的影响。试验结果显示:挤压铸造对过共晶Al-17.5Si合金的组织产生了显著的影响,共晶组织明显细化,初生Si相的数量减少并细化,同时力学性能显著提高。Sr变质后的Al-17.5Si合金在压力下凝固,共晶Si相进一步细化,变为十分细小的纤维状,合金的抗拉强度和伸长率比重力铸造分别提高了59%和328.7%。当P变质处理Al-17.5Si合金挤压铸造成形后,合金组织中却出现了大量的粗大初生Si相颗粒,使得合金的力学性能呈现了降低的趋势。由此确定,挤压铸造过共晶Al-Si合金的最佳变质处理为Sr变质,P变质不适用于挤压铸造成形的过共晶Al-Si合金。     

微量元素对铸造Al-Si合金中Sr变质行为的毒化效应

铸造Al-Si合金在生产、使用、回收及再生过程中往往添加、积累了一定量合金化元素和杂质元素。某些微量元素(Ca、B、Bi、Sb、RE等)往往会和Sr反应形成复杂金属间化合物,减少了参与变质的Sr的含量,降低了Sr的变质效果。Sr在加入到不同合金中,首先要中和微量元素对Sr变质共晶Si的毒化效应,即只要熔体中Sr的含量足够高,仍能够产生良好的变质效果。     

Effects of strontium and boron interactions in Al-7Si alloys

Effects of boron and strontium combined treatment on the microstructure of hypoeutectic Al-7Si alloy have been studied.Experimental results show that strontium has no significant effect on the grain refinement efficiency of boron and the eutectic silicon modification efficiency is not only related to the strontium content but also related to the boron content in the Al-7Si alloy melt.There is a negative interaction between boron and strontium that results in the formation of a strontium-boron-aluminum containing compound,which reduces the effective strontium level and decreases the eutectic silicon modification efficiency substantially.The refinement and modification mechanisms remain unchanged after the combined addition of strontium and boron,Based on the experimental results,a model for assessing the modification level in the Al-Si alloy melts after combined addition of boron and strontium was presented.     

Effects of individual and combined additions of phosphorus, boron and cerium on primary and eutectic silicon in an Al-30Si alloy

The modification of silicon in an Al-30Si alloy was studied using optical microscopy, electron probe micro-analysis, transmission electron microscopy and differential scanning calorimetry. It is found that phosphorus master alloys combined with boron master alloys have good modification effect on primary silicon but no evident modification effect on eutectic silicon, while boron combined with cerium has good modification effect on eutectic silicon. The results of differential scanning calorimetry show that phosphorus, boron or cerium addition and their combined addition have different undercooling effects on eutectic silicon. Many scholars thought that AlP particles were the nuclei of eutectic silicon when phosphorus was enough in the alloy. Our results show that β-(Al,Si,Fe) can still be the nucleus of plate-like eutectic silicon while AlP is the nucleus of primary silicon when there is enough phosphorus in the melt. In addition, the mechanism about the modification was also discussed.     

Modification mechanism of hypereutectic Al-Si alloy with P-Na addition

1　INTRODUCTIONAsastructuralmaterialhavingmanymeritssuchashighfrictionresistance ,highheatresistanceandlowexpansioncoefficient[13] ,hypereutecticAl Sial loyhasbeenattractingattentionofmanyresearchers .However ,forthehypereutecticAl Sialloysproducedwithtraditionalcasting process ,thereareusuallymanycoarseSiparticlesinthematrix ,whichleadtolowtensilestrength ,poorturning propertiesandroughsurfaceaftermechanicalworking[4 ] .Thepre viousresearches[5,6 ] indicatedthat ,forparticulatere inforc…     

Modification of Al-Si alloys: Microstructure,thermal analysis,and mechanisms

In aluminum-silicon cast alloys, the shapes of the silicon phase and the general solidification pattern can be changed by the cooling conditions and by minor additions to the melt. The minor additions either cause modification (sodium, strontium, and other metals) or refine the primary silicon in hypereutectic alloys (phosphorus and elements of Group V-B). Detailed examination of the modified microstructures and analysis of cooling curves are compatible with a modification mechanism involving growth rather than nucleation kinetics.     

Effect of phosphorus and heat treatment on microstructure of Al-25%Si alloy

It is known that phosphorus can refine the primary silicon and heat treatment can spheroidize the eutectic silicon. This paper presents an optimal combination of heat treatment processes and P refinement on hypereutectic Al-Si alloy. The optimal P addition amount, and the solution and aging temperatures for Al-25%Si alloy were obtained through the orthogonal experiment, and their modification effects were discussed. The results show that P addition has the greatest modification effect, followed by aging temperature, and the modification effect of solution temperature is the least. The optimized modification parameters are: addition of 0.6% P, solution at 540 oC and aging at 160 oC . In addition, the cooling curve, superheating and hardness of the alloy were also analyzed.     

Bi和Sr改性Al-7Si-0.4Mg合金显微组织的影响(英文)

研究单独添加Bi和联合添加Bi与Sr在不同凝固条件下对Al-7Si-0.4Mg合金中共晶硅结构的影响。结果表明:添加Bi对共晶硅有细化作用,其细化能力随着Bi质量分数(在<0.5%范围内)的增加而增强。当Bi添加到Sr改性的合金中时,为了得到充分的共晶硅改性,较高的Sr/Bi质量比(至少0.45)是必要的。     

添加Ce与P+Sr复合变质对高硅耐热铝合金组织与性能的影响

研究了添加Ce与P+Sr复合变质对Al-21Si-1．5Cu-0．5Mg-2．5Fe合金显微组织与性能的影响。结果表明:添加1．5％Ce使粗大针状铁相消失,形成富Ce富Fe的鱼骨状相;P+Sr复合变质可使初晶硅平均尺寸由70 mm细化到20mm,共晶硅平均截线长降到2．1 mm,合金室温抗拉强度比未变质前提高21．5％,与P+Sr+Ce复合变质的Al-21Si-1．5 Cu-1．5Ni-2．5Fe-0．5Mg合金相当。     

Sr变质对AlSi6Mg2半固态铝合金组织和性能的影响

利用电磁搅拌装置制备半固态浆料，研究了Sr变质对AlSi6Mg2半固态合金微观组织和力学性能的影响。结果表明：加入0．02％-0．04％Sr，不仅能够改善共晶硅形貌，而且对Mg2Si也有一定的变质作用，使合金的性能明显改善，特别是塑性提高了1倍以上。     

电磁搅拌Al—24%Si合金的显微组织

在常规凝固条件下,Al-24%Si过共晶合金中的初生Si为粗大的板片状,经过激烈的电磁搅拌,初生Si得到明显细化,分布均匀,绝大部分初生Si呈球团状或块状;搅拌功率越大,初生Si越细小和圆整,P变质可以强化电磁搅拌效果,在电磁搅拌条件下,Al-24%Si过共晶合金中的初生Si得以细化和球团化的主要原因是：电磁搅拌引起合金熔体对初生Si的机械破碎,摩擦作用,抑制初生Si择优生长作用,促进初生Si熟化和变质细化作用。     

INFLUENCES OF TRACE ADDITIONS OF STRONTIUM AND PHOSPHORUS ON ELECTRICAL RESISTIVITY AND VISCOSITY OF LIQUID Al-Si ALLOYS

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