Sr含量对4004铝合金铸锭变质效果的研究

研究了Sr加入量分别为0．01％、0．015％、0．02％,变质保温时间分别为60min、80min、100min,对4004铝合金变质效果的影响。结果表明：Sr加入量低于0．015％、变质保温时间小于80min时,合金组织和力学性能均没有达到完全变质状态;Sr加入量0．015％、变质保温时间80min时,4004铝合金变质效果最好,合金组织中的初晶硅转变为细小的圆状或短棒状,共晶硅也由片状或针状转变为纤维状,合金的抗拉强度和伸长率达到最大值193MPa和4．2％;Sr加入量超过0．015％、变质保温时间超过80min时,随着加入量的增加,合金组织开始变得粗大,抗拉强度随着下降。     

Sr复合变质剂对Al—Si合金变质影响的研究

运用正交试验研究Al—10％Sr变质剂对G01铝合金的变质工艺,研究不同变质剂添加量、变质温度、变质时间对变质效果的影响,探索Sr变质剂在Al—Si合金生产中的工艺方法。     

Sr复合变质剂对Al-Si合金变质影响的研究（续）

运用正交试验研究Al-10%Sr变质剂对G01铝合金的变质工艺,研究不同的变质剂添加量、变质温度、变质时间对变质效果的影响,探索Sr变质剂在Al-Si合金生产中的工艺方法。     

Al—Si共晶合金的化学变质剂的概述

介绍了Al-Si共晶合金在生产中的的重要作用,并指出了Al—Si合金变质的原因及意义;研究了各个变质剂在变质处理中的优点和其缺点．分析了变质效果。结果表明：Sr的变质效果比较好,但仍有空洞,故可以采用钠和Sr或者钠、Sr以及稀土复合的变质剂进行变质.     

P、Sr、RE变质对过共晶Al-Si合金组织形态的影响

采用P、Sr、混合RE对含Si量22%～26%的过共晶铝硅合金进行变质处理,利用金相显微镜分析了单一元素变质及复合变质对合金初晶硅和共晶硅组织形态的影响。结果表明,P为初晶硅变质元素,Sr为共晶硅变质元素,RE能同时细化初晶硅和共晶硅;试验发现Sr虽然不能细化初晶硅,但对初晶硅有明显的裂解作用;P和RE复合变质使得初晶硅尺寸减小到25μm,而加入Sr后,由于Sr对初晶硅的裂解作用,使得初晶硅的尺寸减小到15μm,共晶硅大部分呈蠕球杆状或团球状,均匀弥散分布;试验得到了一种初晶硅和共晶硅细化效果均良好的复合变质剂。     

Al-5Ti-1B-4Sr中间合金对Al-8Si合金同时细化和变质效果

采用氟盐法和对掺法成功制备了Al-5Ti-1B-4Sr中间合金,采用X射线衍射(XRD)和扫描电镜(SEM)分析了Al-5Ti-1B-4Sr中间合金的组织及相组成。通过改变Al-5Ti-1B-4Sr中间合金细化变质保温时间,采用微观组织分析和宏观组织分析方法,研究了Al-5Ti-1B-4Sr中间合金对Al-8Si亚共晶铝硅同时细化和变质的效果。研究结果表明,Al-5Ti-1B-4Sr中间合金中含有Al_3Ti相、TiB_2相和Al_4Sr相,Al-5Ti-1B-4Sr中间合金对亚共晶铝硅合金有良好的同时细化变质效果。Al-5Ti-1B-4Sr中间合金可使共晶硅从针状或板片状形貌转变为纤维状或块状。与未变质试样相比,细化变质时间为10 min时,Al-8Si合金中针状或板片状共晶硅显著减少;变质时间超过20 min时,看不到针状或板片状共晶硅存在;当变质时间达到80 min时,部分针状或板片状共晶硅再次出现。随着Al-5Ti-1B-4Sr细化变质保温时间的变化,α-Al的二次枝晶臂间距和共晶团尺寸先减小后增大,细化变质保温时间为30 min时效果最好。Al-5Ti-1B-4Sr中间合金对亚共晶铝硅合金细化变质的孕育期为10~20 min,衰退期为60 min。     

Zr-Sr复合变质对高硅Mg-Si-Zn镁合金组织的影响

为了改善高硅Mg-Si-Zn合金的性能,通过实验添加元素Sr、Zr,对Mg-Si-Zn合金进行单一和复合变质.分析了Mg_2Si初生相和共晶Mg_2Si的形貌与尺寸,研究了高硅Mg-4Si-4Zn合金的组织变化规律.结果表明:Sr可将Mg-4Si-4Zn合金中粗大的初生Mg_2Si枝晶变为规则的块状,树枝晶尺寸由长90～130μm,宽50～70μm变为对角线长度为20～50μm,复杂汉字状的共晶Mg_2Si变质为细小的棒状;Sr在凝固过程中通过在Mg_2Si表面占位来阻碍其生长,当Sr加入量超过0.75%后合金组织中出现Mg_xSr_ySi_z相,使Sr变质效果下降.经过Zr-Sr复合变质,Mg-4Si-4Zn镁合金初生Mg_2Si相形貌由不规则状转变为对称的六边形状,具有尖锐棱角的初生相逐渐减少,当Zr添加量达到0.9%时,变质效果最好,Mg_2Si相最为圆整.     

ZL101合金锶变质效果及热处理工艺的改进

对现场生产的ZLl01合金铸件材质进行了全面分析，针对存在的产品成分不准，变质效果不好，力学性能不合格的问题，通过改进合金的锶变质工艺和热处理工艺，改善了合金的组织和性能，达到了对材料的成分、性能的各项要求。     

稀土Nd对铸造铝硅合金变质作用的长效性及重熔性研究

以稀土元素Nd为变质剂,采用金属型铸造工艺制备铸造铝硅合金ZL101,并通过金相显微镜、扫描电镜、布氏硬度计和电子万能试验机研究变质时间及重熔次数对合金显微组织和力学性能的影响.结果表明,稀土Nd对合金具有较好的变质作用,并具有长效性和重熔性,变质6h及重熔4次后合金中的共晶硅组织仍呈小片状的变质状态,且合金硬度及拉伸性能均未受明显影响.变质不同时间及重熔不同次数的合金拉伸试样均为解理断裂.     

不同变质剂对Al—Si—Mg—Cu合金组织及性能的影响

铸造铝合金的变质处理是生产中广泛采用的工艺过程。目前工业上采用的变质剂以Na为主,但是这在工艺上存在着一系列至今无法克服的缺点,如变质有效期短,具有腐蚀性等等。因此,人们正在广泛探索新的变质剂,如RE、Sr和Sb等。但就目前看到的资料,这些研究大都注重对铸态下组织形态     

Study on Improving Solidification Structure of Rare Earth Al-Si Alloys with Electropulse Acting on Liquid Alloy

Electropulse modification (EPM) process, a new physical field method for improving the solidification structure of metals was introduced.Different from other research, EPM is only acting pulse current on melt under liquid state.The solidification structure of Al-Si alloys, A1-Cu alloys,cast iron and steel can be modified obviously with this method: the solidification structure of ZL101 alloy presented the Na and Sr modification and the mechanical properties were enhanced; a large number of primary silicon appeared in the microstructure of ZL109 alloy; the equiaxed grain zone was expanded and the grains were fined in Al-5.0wt% Cu alloy; the graphitization took place in solidification process of molten cast iron; the grain sizes of solidification structure of T8 steel were reduced significantly and the shape of steel pearlites also changed; the equiaxed grain zone increased to 88% from original untreated 19%, the equiaxed grains were fined and the intercrystalline crack was avoided in concasting billet by continuously treating liquid electrical sheet steel in tundish.Effects of rare earths on casting Al-Si alloys were also summarized.The method of modifying the solidification structure of rare earth Al-Si alloys with EPM in producing the alloys was proposed.     

The effect of Sr and Fe additions on the microstructure and mechanical properties of a direct squeeze cast Al-7Si-0.3Mg alloy

This article describes the results of an investigation into the microstructure and mechanical properties of a gravity die cast and direct squeeze cast LM25 alloy (Al-7Si-0.3Mg-0.3Fe). The direct squeeze cast LM25 alloy has superior mechanical properties compared to the gravity die cast LM25 alloy, especially with regard to ductility, which is increased from ∼1.7 pct for the gravity die cast LM25 alloy to ∼8.0 pct for the direct squeeze cast LM25 alloy in the T6 heat-treated condition. This increase in ductility is due to (1) the removal of porosity, (2) a decrease in Si particle size, and (3) a refinement of the Fe-Si-aluminide particles. High cooling rates in direct squeeze casting result in quench modification of the Si particles, such that chemical modification with Sr or Na may not be required. In addition, direct squeeze casting is more tolerant of Fe impurities in the alloy, due to the formation of smaller Fe-Si-aluminide particles than those in gravity die cast material. The direct squeeze cast LM25+Fe alloy (Al-7Si-0.3Mg-1.0Fe) has a ductility of ∼6.5 pct, compared to that of ∼0.5 pct for the gravity die cast LM25 + Fe alloy in the T6 heat-treated condition. This increase in tolerance to Fe impurities can lead to a substantial reduction in manufacturing costs due to (1) reduced raw-material costs, (2) reduced die sticking, and (3) improved die life.     

A study of the influence of mischmetal additions to ai-7si-0.3mg (lm 25/356) alloy

This article deals with the effect of 0.25-1.5 wt pct mischmetal (MM) addition on the mechanical properties, microstructure, electrical conductivity, and fracture behavior of cast Al-7Si-0.3Mg (LM 25/356) alloy. Modification of eutectic silicon by MM is compared with strontium modification in terms of microstructure, mechanical properties, and fading behavior. Loss of magnesium encountered on holding the molten alloy and its resultant effect on mechanical properties of alloys modified with MM and Sr are compared with those in the unmodified alloy.     

A356合金力学性能的工艺研究

叙述了金属锶对A356合金的变质处理，采用复合净化工艺，型腔多点冷却等技术措施，明显提高A356铝合金的力学性能。研究得出一个比较成熟的A356铝合金复杂零件的生产工艺，可供广大材料工作者借鉴。     

The effect of na and Sr modification on surface tension and volumetric shrinkage of A356 alloy and their influence on porosity formation

Modification of the eutectic Si in Al-Si foundry alloys by adding strontium or sodium is, unfortunately, accompanied by an increase of porosity in the casting. In an attempt to understand the nature of this problem, this study used a sessile-drop method to investigate the effect of Sr and Na on surface tension and volumetric shrinkage, two probable causes of porosity occur-rence. The addition of 0.01 wt pct Sr and 0.005 wt pct Na to A356 alloy decreases the surface tension of the liquid by about 19 and 10 pct, respectively, and may increase the volume shrink-age by about 12 pct. These changes to surface tension and volumetric shrinkage promote the early formation of the pores during solidification and give the availability of a longer period of growth prior to complete solidification, resulting in a larger pore size. The effect of surface tension on the pores is more significant than volumetric shrinkage. Although the predicted pore diameter increases with lower surface tension or higher volumetric shrinkage, these two effects alone do not seem able to completely account for the observed increase in porosity that is associated with modification.     

亚共晶Al-Si合金的Sr变质处理工艺

对亚共晶Al-Si合金进行Sr变质处理,试验结果表明:变质处理能使合金的组织细化,力学性能得到提高。