Effect of neodymium on primary silicon and mechanical properties of hypereutectic Al-15%Si alloy

The mechanical properties of hypereutectic Al-Si alloys are mainly determined by size and morphology of the primary silicon phase. So, optical microscopy (OM) and X-ray diffraction (XRD) were adopted to study affection of Nd on primary silicon of hypereutectic Al-15%Si alloy in this paper. The results of OM showed that pure Nd could effectively refine primary silicon of hypereutectic Al-15%Si alloy. When Nd addition was 0.3%, the average size of primary silicon reduced from 20-40 μm of initial sample to 10-20 μm of modified sample. XRD pattern showed that no new phase was formed after Nd modification. The results of mechanical properties test showed that whole properties of modified samples were significantly improved. Tensile strength increased about 32.6% from 147 MPa to 195 MPa. Elongation was increased about 160% from 1.0% to 2.6%. The improvement of mechanical properties should attribute to primary silicon refinement after modification.     

Effect of erbium on properties and microstructure of Al-Si eutectic alloy

Eutectic Al-12.6 wt.%Si alloys with various contents of the rare earth dement Er were prepared by the conventional casting technique.The effect of Er on the microstructure and properties of the eutectic Al-Si alloys was investigated using optical microscopy,scanning electron microscopy as well as the friction and wear tests.It was found that the addition of Er obviously improved the anti-wear properties,and reduced the friction coefficient of the alloys.The appropriate addition of Er would change the size and shape of the eutectic silicon,and thereby refine the microstructure of the Al-Si alloys.The refinement mechanism was also discussed.     

Effect of neodymium stearate on cure and mechanical properties of epoxidized natural rubber

The effect of neodymium stearate (NdSt) on cure and mechanical properties of expoxidized natural rubber with 25 mol.% epoxida-tion (ENR25) was studied in the concentration range of 0 to 2 phr, and the relationship between structure and mechanical properties of ENR25 vulcanizates was also discussed. Neodymium sterate was synthesized by saponification of stearic acid with newly formed rare earth hydroxide in water medium, and the structure of NdSt was investigated by Fourier transform infrared spectroscopy (FTIR). Crosslinking den-sity of vulcanized natural rubber was studied by equilibrium swelling method. The results indicated that the interaction force between carbox-ylic ion of NdSt prepared in the lab and Nd ion was mainly ionic bond through FTIR analysis. NdSt could accelerate the vulcanization of ENR25 and influence the network structure of ENR25 vulcanizates. The incorporation of 1 phr NdSt for ENR25 vulcanizates showed the op-timal aging resistnce.     

Microstructure and mechanical properties of Mg-Zn-Mn-Sn-Nd wrought alloys

The microstructure and mechanical properties of as-cast and extruded Mg-6Zn-1Mn-4Sn-xNd(x=0, 0.5, 1.0, 1.5) alloys were investigated by means of optical microscopy(OM), X-ray diffraction(XRD), scanning electron microscopy(SEM) and tensile test. The results showed that the dendrites sizes of these alloys were decreased by the addition of Nd. The phase compositions of the as-cast Mg-Zn-Mn-Sn-Nd alloys were dendritic α-Mg, MgZn2, Mg2 Sn, T phase and MgSnNd ternary phase. The mechanical properties of the as-extruded alloys were improved due to the refined equiaxed grains and dispersive Mg2 Sn and MgSnNd second phases. The comparison of the theoretical yield strength with the experimental yield strength revealed that the yield strength model of the as-extruded alloys should be modified as σys =σMg +σgb +σss +σsp.     

稀土Nd对AZ 31镁合金铸态组织和力学性能的影响

利用气氛电阻炉制备了AZ 31-xNd合金(x=0.05%,0.1%,0.2%,0.4%,0.6%),采用光学显微镜(OM)、扫描电子显微镜(SEM)和电子能谱分析仪(EDS)对不同Nd含量的实验合金进行了显微组织观察和分析,结果发现,Nd在AZ 31-xNd合金中形成了Al_3Nd和Mg_(12)Nd相,这些含Nd相导致AZ 31镁合金在凝固过程中的晶粒细化,从而提高了AZ 31镁合金的铸态室温力学性能,随着Nd含量的增加,合金的铸态室温抗拉强度极限和延伸率均先升高后降低.     

Effects of Nd on microstructure and mechanical properties of as-cast Mg-8Li-3Al alloy

Effects of Nd on microstructure and mechanical properties of as-cast Mg-8Li-3Al alloy were investigated by OM,X-ray diffraction(XRD),EPMA,scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS).The results showed that the dendrites sizes of α phase were decreased by the Nd addition.When the amount of addition Nd was 1.6 wt.%,the alloy with the smallest α phase was obtained.The refining mechanism mainly owed to the increasing constitutional supercooling at the solidification front.Furthermore,the compound Al 2 Nd generated by the reaction of Al and Nd,which distributed at the phase boundary and inside β phase,could also restrain the growth of α phase.Nd could improve the tensile strength and elongation of Mg-8Li-3Al alloy,however,excessive Al 2 Nd might also become crack source and decrease the elongation.     

Al-24%Si合金半固态等温搅拌时的微观组织

研究了Al-24% Si合金在半固态等温电磁搅拌下组织的变化规律.实验分冷却过程不搅拌和冷却过程搅拌2种.保温温度为577℃,在此温度下,搅拌时间长达40 min.结果发现,搅拌过程中同时发生初生硅相的破碎和聚合行为,当等温搅拌时间超过20 min后初生硅相粒子的尺寸变化不大,其分布也趋于均匀;组织中出现了球状的α相.     

Study on microstructure and mechanical properties of ZL107 alloy added with yttrium

The effects of Y on the microstructure and mechanical properties of ZL107 alloy were investigated using optical microscope, scanning electron microscope (SEM), Brinell hardometer, and MTS 810-22M tensile testing machine in this paper. The results showed that after Y was added to ZL107 alloy, the size of α-Al dendritie reduced, the acicular eutectic Si became short rod-shaped or granular, and the number and size of the blowholes obviously reduced. The mechanical properties of ZL107 alloy firstly increased and then decreased with Y content increasing. When Y content was 0.1 wt.%, the tensile strength and hardness of the alloy were maximum.     

复合变质对过共晶Al-24％Si合金组织的影响

对过共晶Al-24％Si合金进行了单一磷、稀土及磷和稀土双重复合变质处理。实验表明,磷和稀土双重复合变质能够有效的细化合金的组织,变质后合金中的初晶硅晶粒平均尺寸由变质前的60μm变为20μm,且分布均匀．共晶硅也由长针状变为短杆状。同时对磷和稀土的双重复合变质机理做了初步探讨。     

Effect of cerium on microstructure,wetting and mechanical properties of Ag-Cu-Ti filler alloy

Effect of cerium on microstructure,mechanical and wetting properties of Ag-Cu-Ti filler alloy was researched with optical microscopy,scanning electron microscopy and X-ray diffraction.The results indicated that addition of cerium accelerated alloying of the filler alloy,enlarged supercooled region,caused microstructural refinement and dispersed distribution of intermetallic compounds.It resulted in the increase in microhardness and shear strength of Ag-Cu-Ti filler alloy.At the same time,cerium improved wet...     

Microstructure and mechanical properties of Mg-7Zn-3Al alloy with Nd and Y additions

The effects of combined addition of 0.6 wt.% Nd and 0.4 wt.% Y on the microstructure and mechanical properties of Mg-7Zn-3Al alloy were investigated.The results indicated that the Nd and Y addition led to obvious dendrite coarsening.However,it could modify the morphology and distribution of-Mg 32(Al,Zn) 49 intermetallics.Moreover,Al 2 REZn 2 phase could be introduced into the alloy with the Nd and Y addition.With the effective second-phase strengthening,the ultimate tensile strength and elongation in as-cast state can be improved by the Nd and Y addition.After ageing treatment,the alloy with the Nd and Y addition exhibited better precipitation strengthening effects by forming finer MgZn 2 and Mg 32(Al,Zn) 49 precipitates into the-Mg matrix.As a result,the yield and ultimate strength of Mg-7Zn3Al-0.6Nd-0.4Y alloy could be increased to 182 and 300 MPa by peak-ageing treatment.     

Effect of rolling and heat treatment on microstructure and mechanical properties of Mg3.5Y0.8Ca0.4Zr alloy

The effect of rolling and heat treatment on microstructure and mechanical properties of Mg3.5Y0.8Ca0.4Zr alloy was investigated.With the addition of 0.4Zr,the average grain size of the as-cast alloy was markedly refined to 5-10 μm.After hot rolling process,the grain size of Mg3.5Y0.8Ca0.4Zr alloy was refined further into 3-5 μm and the tensile strength was enhanced while the plasticity was degraded because the accumulation of rolling reduction increased the density of twins,and refined the grain structures.After the solution heat treatment at 743 K,the elongation of alloy was greatly enhanced from 3% to 17%.     

电脉冲孕育处理对Al-5%Cu-0.8%Mn合金组织及性能的影响

通过凝固组织观察、力学性能测试、断口分析等实验,研究了不同电脉冲孕育处理对Al-5%Cu-0.8%Mn合金组织和性能的影响.实验结果表明,不同电脉冲处理参数均使Al-5%Cu-0.8%Mn合金凝固组织细化,单位面积晶粒数提高2倍以上;合金力学性能较未处理试样明显改善,抗拉强度增加了21%~35%,伸长率提高1.8~2.5倍;且当脉冲电压500V、时间30s、频率3Hz时,合金的凝固组织细化效果最好,力学性能最佳.     

Microstructure and mechanical properties of Mg-10Y-2.5Sm alloy

The microstructure and mechanical properties of aged Mg-10Y-2.5Sm alloy were investigated.The results showed that the microstructure of the alloy consisted of α-Mg matrix and Mg24Y5 phase,and fine Mg24Y5 particles distributed in α-Mg matrix uniformly and dispersedly.Sm enhanced α-Mg matrix and Mg24Y5 phase by solid solution effect.At 200-300 oC,the ultimate tensile strengths were more than 200 MPa and the elongations were about 3%.Compared with those at room temperature,the mechanical properties had no obvious changes.     

Effects of precipitates on grain size and mechanical properties of AZ31-x% Nd magnesium alloy

The effects of precipitates on grain size and mechanical properties of as-cast AZ3 1-x%Nd magnesium alloy were investi- gated, and the affecting mechanism was also discussed. The results indicated that Al2Nd phase, AlllNd3 phase and a few AI-Mn-Nd-Fe phase were furmed when adding 0.38 wt.%-1.46 wt.% Nd into AZ31 melt, coarse AI2Nd transformed into Al11Nd3 gradually with the increasing of Nd content. Due to structure and size transformation and content increasing of AI-Nd phase, the grain size of AZ31-x% Nd alloy increased firstly, and then decreased with the increment of Nd content. After reaching a minimum value, once again it rose up, provided that Nd content was further increased. The tensile property reached its optimal value when the adding amount of Nd content was 1.05 wl.%, however, adding excessive amount of Nd deteriorated both ultimate strength and elongation ofAZ31 alloy.     

Microstructure and mechanical properties of as-cast and heat treated Mg-15Gd-3Y alloy

The microstructure evolution and mechanical properties of Mg-15Gd-3Y alloy were investigated in the as-cast and heat treated conditions.The microstructure evolution from as-cast to cast-T4 states involved α-Mg solid solution+Mg5(Gd,Y) phase→α-Mg supersatu-rated solid solution+rare earths compound Mg3(Gd1.26,Y0.74)→α-Mg supersaturated solid solution+rare earths compound Mg3(Gd0.745,Y1.255).It showed that 480 oC/4 h was the optimal solution treatment parameter.If the solution temperature was high or the holding time was long,such as 520 oC/16 h,an overheating phenomenon would be induced,which had a detrimental effect on the mechanical properties.When age-ing at 225 and 200 oC,the alloy would exhibit a significant age-hardening response and great long-time-age-hardening potential,respectively.The best mechanical properties were obtained at the parameters of 480 oC/4 h+225 oC/16 h,with the UTS of 257.0 MPa and elongation of 3.8%.     

Effects of heat treatments on microstructure and mechanical properties of Mg-15Gd-5Y-0.5Zr alloy

Microstructure and mechanical properties of Mg-15wt.%Gd-5 wt.%Y-0.5wt.% Zr alloy were investigated in a series of conditions. The eutectic was dissolved into the matrix and there was no evident grain growth after solntionized at 525 ℃ for 12 h. The evolution of the phase constituents from as-cast to cast-T4 was as follows： α-Mg solid solution＋Mg5（Gd,Y） entectic compound→α-Mg solid solution＋ spheroidized Mg5（Gd, Y） phase→α-Mg supersaturated solid solution＋cuboid-shaped compound （Mg2Y3Gd2）. And the precipitation sequences of Mg-15Gd-5Y-0.5Zr alloy were observed, according to the hardness response to isothermal ageing at 225-300 ℃ for 0-128 h.     

Effects of cerium and phosphorus on microstructures and properties of hypereutectic AI-21% Si alloy

The influences of P and rare earth (RE) complex modifier on the microstructure and mechanical properties of hypereutectic Al-21%Si alloy were studied. The ingots were made by metal mold casting and the proportion of Ce+P ingredient was different. The result showed that the size of grains could be refined obviously by the Ce+P modifier and the effect of phosphorus was more intensive. The primary silicon crystal was refined, while the needle-like eutectic silicon was turned fibrous or short. The alloy mechanical properties had the best performance when 0.08%P and 0.6%Ce were added. The modification of primary silicon grains mainly depended on the heterogeneous nucleation mechanism, and the metamorphic mechanism of eutectic silicon was explained by adsorbing-twinning theory. The strengthening mechanism of experimental alloy was also discussed. The σb, 20 ℃ increases from 236.2 to 287.6 MPa and σb , 300 ℃ increases from 142.5 to 210 MPa.     

Effect of rare-earth oxides on properties of silicon nitride obtained by normal sintering and sinter-HIP

This paper presented the microstructure,mechanical properties and oxidation behavior of silicon nitride obtained by both conventional sintering and sintering followed by hot isostatic pressing(HIP).Silicon nitride with additives such as 5 wt.% Al2O3 and 5 wt.% Ln2O3(Ln= La,La concentrate,Gd or La+Gd) were studied.The results revealed that Gd2O3 additions increased the formation of elongated grains of β-Si3N4,the fracture toughness and oxidation resistance.La2O3 additions led to higher densification and hardness values,while addition of La2O3 concentrate promoted the formation of materials with intermediate properties,compared to the other studied compositions.Hot isostatic pressing increased the hardness but decreased the fracture toughness of the material,mainly because it allowed residual pores to close and also reduced the average aspect ratio of β-Si3N4 grains.