Microstructure and Properties of Mg-10% Al-(0～3% )Di Alloys

The effects of didymium(Nd:Pr=3:1)on the microstructure and mechanical properties of Mg-10%Al alloy were studied with the additions of 0～3%Di. The small block-like Al2(Nd,Pr) phase appears in 1%Di alloy, the block-like Al2(Nd,Pr) and needle-like Al11(Nd,Pr)3 phases appear synchronously in 2%Di and 3%Di alloys, while the network of (Mg17Al12) β phase is broken up. The tensile properties can be improved with the addition of didymium. When the addition of didymium in Mg-10%Al alloy reaches 2%, the alloy exhibits the best combination of strength and ductility, but the strength and ductility drop at the addition of 3%Di due to the obvious increase of the size and quantity of the needle-like Al11(Nd,Pr)3 phase.

Mg对铸造Al-10%Fe合金初生富铁相形貌的影响

研究了Mg元素对铸造A1-10％Fe过共晶合金初生Al_3Fe相形态的影响。研究发现,加入Mg对初生Al_3Fe相生长产生影响,由原来的发达针状向树枝状→小针(片)状、不规则块状转变。对Mg元素的影响机理做了分析。

稀土钪对Al-10Mg合金性能的影响

通过微观分析及力学性能测试等方法,研究了添加稀土元素钪对Al-10Mg合金(ZL301合金)显微组织及力学性能的影响。结果表明,加入适量的钪元素后明显细化了Al-10Mg铸造合金的显微组织,主要是由于钪元素与Al形成颗粒状的稀土化合物Al_3Sc相,使合金中Al_3Mg_2相减少;经435℃×16h固溶处理后,Al_3Mg_2相基本溶解,稀土化合物Al_3Sc相热稳定性较高并未溶解,合金抗拉强度进一步得到提高。当钪元素的添加含量为0.4%时,Al-10Mg合金综合性能最为优良。

稀土元素La对Al-10Mg合金组织及力学性能的影响

研究了稀土元素La对Al-10Mg合金铸态及固溶处理态显微组织及力学性能的影响。结果表明,La的加入使Al-10Mg合金晶粒组织细化,同时析出Al11La3化合物。经固溶处理后,Al3Mg2相溶解。随La添加量的增加,合金铸态和固溶处理态的力学性能呈先增后降的趋势。添加0.35%的La及435℃×15 h的固溶处理可显著提高Al-10Mg合金的力学性能。

开孔泡沫Al-10%Mg合金的动态压缩行为的研究

用 Hopkinson压杆实验装置对开孔结构的泡沫 Al- 10 % Mg合金进行了动态压缩实验 ,在应变率为准静态、80 0 s- 1 和 2 0 0 0 s- 1 条件下测量了动态和准静态压缩应力 -应变曲线 ,研究了这种铝合金泡沫的动态压缩行为 ,并分析了其应变率效应。结果表明 :在动态和准静态压缩下 ,泡沫 Al- 10 % Mg合金的压缩 σ- ε曲线均表现出弹性变形段、平缓段和紧实段三阶段特征 ;泡沫 Al- 10 % Mg合金具有明显的应变率敏感性 ,随应变速率的提高 ,相同应变量下的流动应力上升。

热处理工艺对Al-10%Si-3%Cu-0.3%Mg合金微观组织和性能的影响

研究了热处理工艺对Sr变质Al-10%Si-3%Cu-0.3%Mg合金组织和和力学性能的影响。通过显微组织观察、力学性能检测及断口形貌分析,对Al-10%Si-3%Cu-0.3%Mg合金硬度和抗拉强度进行了研究。结果表明,在500℃(或500℃×4 h+515℃)下固溶处理,随时间的延长,富铜相的溶解量增多,同时在535℃下出现了富铜相的熔化。同时还发现与一步固溶工艺相比,两步固溶处理工艺下富铜相能够充分溶解,性能更好。经500℃保温4h+515℃保温8h处理性能最佳;对该试样再进行175℃×4h时效处理后,试样抗拉强度和塑性都明显提高。

稀土La对Al-10Mg合金铸态组织与性能的影响

研究了添加稀土La对Al-10Mg合金铸态显微组织和力学性能的影响,结果表明:加入质量分数为0.3%-0.5%的La能够细化铸态Al-10Mg合金的晶粒,并形成颗粒状及短杆状Al-La化合物,提高合金力学性能,当La添加量超过0.7%时,合金晶粒出现粗化,Al-La化合物转变为沿晶界连续分布的粗大网络状形态,La对合金的强化效果减弱。

Al-10%Mg中间合金细化Al-5%Fe合金的研究

通过改变Al-10%Mg中间合金晶粒细化剂加入量和熔体保温时间,研究了过共晶Al-5%Fe合金微观组织形态及力学性能。试验表明,在过共晶Al-5%Fe合金中加入Al-10%Mg中间合金细化剂,当加入量为1.2%、保温时间为90 min时,细化效果仍较好,Al-5%Fe合金中初生A13Fe相由粗大板条状变为花朵状和颗粒状,尺寸明显减小,材料的强度和塑性明显提高。

Ce对Al-18%Si-10%Mg合金显微组织与力学性能的影响

研究了稀土元素Ce对Al-18%Si-10%Mg合金显微组织和力学性能的影响。结果表明,在合金中添加适量的Ce对初生Mg2Si和初生硅都有良好的变质作用。当Ce添加到0.8%时,初生的Mg2Si颗粒由粗大十字状或者不规则的多面体转变成为细小规则的块状,初生硅和共晶硅颗粒的尺寸也减小。随着稀土元素Ce的添加,合金的抗拉强度和硬度均得到了提高,增幅分别为29.7%和15.8%。同时摩擦系数以及磨损量则逐渐降低,降幅分别为10.5%和74.5%。

Dynamic recrystallization during hot torsion of Al-4Mg alloy

Binary Al-4Mg alloy have been deformed by hot torsion at 300-500 deg C andstrain rates of 0.006-1.587 s^(-1) to a true strain of 5.5. The specimens were annealed in vacuumfor 1.5 h at 500 deg C and then water quenched. The study indicates that the dynamicrecrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter(Zener-Hollmon Parameter), i.e. 19.3 <= lnZ <=24.8. Increasing the strain rate at higher deformationtemperature or reducing the strain rate at lower deformation temperature accelerates the occurrenceof dynamic recrystallization in the alloy.

Microstructural evolution of pre-twinned Mg alloy with annealing temperature and underlying boundary migration mechanism

This study investigates the variations in the microstructural characteristics of a pre-twinned Mg alloy with the temperature of the subsequent annealing treatment.To this end,a rolled AZ31 alloy is compressed to 3%plastic strain along the rolling direction(RD)to activate{10-12}twinning and is subsequently annealed at 200,250,300,350,and 400℃.Numerous{10-12}twins are formed throughout the compressed material,leading to the formation of a RD-oriented texture.At an annealing temperature of 200℃,no microstructural variations occur during annealing.As the annealing temperature increases from 250 to 400℃,the residual strain energy and remaining twin boundaries of the annealed material decrease owing to the promoted static recovery and the increased area fraction of twin-free grown grains.Consequently,an increase in the annealing temperature results in a gradual microstructural transition from a fully twinned grain structure to a completely twin-free grain structure.The microstructural evolution during annealing is predominantly governed by the movement of high-angle grain boundaries via a strain-induced boundary migration mechanism,and a few twin boundaries migrate above 350℃ because of their lower boundary energy.The boundary migration behavior and resultant microstructural evolution are discussed in detail based on the variations in boundary mobility and driving force for boundary migration with annealing temperature.

Unveiling the planar deformation mechanisms for improved formability in pre-twinned AZ31 Mg alloy sheet at warm temperature

To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation, the stretch forming is conducted at 200 ℃. Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm. The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states. The Schmid factor for deformation mechanisms are calculated, the results reveal that planar stress states extremely affect the Schmid factor for {10-12}twinning. The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet, especially under the planar extension stress state in the outer region. Consequently, the thickness-direction strain is accommodated better. The dynamic recrystallization(DRX) type is continuous DRX(CDRX) regardless of the planar stress state. However, the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect {10-12} twinning relation due to the planar compression stress state and the CDRX. The basal texture is weakened when the planar stress state tends to change the texture components.

Microstructure of the Hypoeutectic Al-Mg Alloy Solidified at 4 GPa High Pressure

High pressure solidification rules of Al-Mg alloy needs to be discussed further for its wide range of application. Microstructures and phases of Al-25wt% Mg alloy solidified at 4 GPa were studied by optical microscope,X-ray diffractmeter,energy dispersive X-ray spectroscopy and transmission electron microscopy( TEM). The microstructure evolution mechanism of Al-25Mg alloy under high pressure was analyzed. The result shows that the alloy consists of α-Al phase and Al 3 Mg 2 phase under normal pressure. However,only Al 12 Mg 17 phase forms without Al 3 Mg 2 phase at 4 GPa. In addition,Mg concentration in α-Al phase increases and that of the lattice constant also increases. The α-Al dendrite presents the broken arms under normal pressure, after high pressure solidification,the morphology of the dendrite tends to integrate and the size of the dendrite arms

Effects of Pressure on the Solidification Microstructure of Mg65Cu25Y10 Alloy

The Mg65Cu25Y10 melts were quenched at a temperature of 973 K under various pressures in the range of 2-5 GPa and ambient pressure. The microstructure of the solidified specimens has been investigated by X-ray diffraction, transmission electron microscope and electron probe microanalysis. Experimental results show that the pressure has a great influence on the solidification microstructure of the Mg65Cu25Y10. At ambient pressure, the solidification products are Mg2(Cu,Y) and a very small amount of Y2O3 inclusion. As the pressure is above 2 GPa, a new Cu2(Y,Mg) phase appears, while Y2O3 is not observed at the pressure of 3, 4 and 5 GPa. When the pressure increases from 2 GPa to 5 GPa, the grain sizes of Mg2(Cu,Y) and Cu2(Y,Mg) decrease from 125, 96 nm to 80, 7 nm, respectively. The mechanisms for the effects of the pressure on the phase evolution and microstructure during solidification process of Mg65Cu25Y10 alloy have been discussed.

Al-10Sr中间合金形态对AlSi7Mg合金变质组织的影响

研究了不同成形方式的Al-10Sr中间合金(圆块状、长杆状)对Al Si7Mg合金变质效果及熔炼过程收得率的影响,并分析产生差异的原因,结果表明:采用圆杆状Al-10Sr变质的合金经热处理后(T6),Al Si7Mg合金中Si相呈更加细小的、均匀的颗粒状分布。熔炼过程中发现,圆杆状中间合金在同样条件下的收得率要更高,平均收得率达98.1%。

High-strength friction stir welding of selective laser melted AlSi10Mg alloys

Selective laser melted AlSi10Mg alloys with eutectic network structures were successfully joined by friction stir welding.Sound butt-lap joints have been achieved.A novel enlarged pin was designed to overcome kissing bonding defects and increase interfacial bonding area.The hook defect in a conventional butt-lap joint was avoided due to the limitation of the upward flow of interfacial materials,and the interfacial joining width was 2.5 times of the plate thickness.The eutectic Si network structure was broken into the re-dispersed rich-Si phases,improving joint performance.The ultimate tensile strength reached 83.1%of the matrix,higher than those of conventional melting techniques.

Efficiency of Chalcone Compounds Inhibitors for Acid Corrosion of Al and Al-3.5Mg Alloy

Corrosion inhibition of Al and Al-3.5Mg alloy by organic compounds, namely chalcones in hydrochloric acid solutions has been investigated by rapid polarization technique and weight loss method. Polarization measurements show that, the inhibitors act cathodically both in case of Al and Al-3.5Mg alloy. It was found from the weight loss measurements that, the inhibition efficiency depends on the substituent in the chalcone compound. The relative inhibitive efficiency of these compounds has been explained on the basis of structure dependent electron donor properties of the inhibitors and the metal inhibitor interaction on the surface. The inhibition efficiency ranges from 16 to 64% for Al and from 30% to 91% for Al-3.5Mg alloy

RHEOLOGICAL BEHAVIOR OF PARTIALLY SOLIDIFIED AL-10%Cu ALLOY

The rheological behavior of partially solidified Al-10% Cu alloy is in-vestigated.It is found that the slurry presents the character of a psoudoplastie fluid inisothermally holding and the apparent viscosity increases with increasing cooling ratein continuously cooling.The effect of cooling rate on the apparent viscosity decreasesin high stirring rate range.The measured value of apparent viscosity is influenced bythe diameter of the screw propeller.

Dynamic Mechanical Behavior and Microstructural Evolution of the Al-6Mg Alloy Subjected to Three Treatment Conditions

The mechanical properties of Al-6Mg alloy with three treatment states （H112, O and cold-extruded states） were investigated at room and high temperatures using an INSTRON machine and a Split Hopkinson Pressure Bar （SHPB）. Stress-strain curves of the alloy with different processes were obtained at a quasi-static strain rate of 5×10-4 s-1and dynamic strain rates of 1 400-4 200 s-1, respectively. The results suggest that, at room temperature, the three processed Al-6Mg alloys are all low sensitive to strain rate. The O state Al-6Mg alloy （Al-6Mg-O） exhibits the most ductility, while the cold-extruded Al-6Mg alloy （Al-6Mg-C） displays the highest strength. At elevated temperatures, the yield stresses and the differences in yield stress of the three processed alloys all decrease with increasing temperature under the quasi-static strain rate of 5×10-4 s-1. Based on test results, modified Johnson-Cook （JC） constitutive models for the three processed Al-6Mg alloys were developed. The microstructures before and after deformation were examined by electron backscattered diffraction （EBSD） and further dynamic recrystallization （DRX） at the strain rate of 3 300 s-1 was discussed.