共查询到20条相似文献,搜索用时 203 毫秒
1.
2.
变质处理镁合金在SIMA法中的组织演变 总被引:1,自引:0,他引:1
试验研究了经过变质处理的AZ91D镁合金利用SIMA法制备半固态浆料,在等温热处理过程中的组织演变。结果表明:在AZ91D镁合金中加入Ce、Sb和两者的混合物后,合金铸态组织明显细化,添加0.6%(Ce Sb)的混合物,能得到较好的细化效果,晶粒尺寸为60~70μm。变质处理可促进形变合金组织中的初生相在半固态等温热处理过程中由枝晶向粒状晶的转变,获得更加细小并且均匀的球状组织(50~55μm),可以满足后续的半固态成形的基本要求。 相似文献
3.
《特种铸造及有色合金》2017,(1)
以AZ91D镁合金屑料为原料,采用热压制工艺和半固态等温处理制备半固态坯料,通过显微组织观察和定量金相分析研究了半固态组织均匀性及组织演变。结果表明,在热压制工艺参数下,压坯密度为1.76g/cm3,相对密度可达98%,晶粒得到显著的细化,组织均匀分布。经半固态等温处理后,组织中平均颗粒尺寸为98.6μm,平均颗粒形状因子为1.6,半固态组织分布均匀。半固态组织演变分为3个阶段:Mg17Al12相的溶解,高溶质区域的熔化,固相颗粒的球化和长大。 相似文献
4.
5.
6.
AZ91D镁合金在半固态等温热处理中的组织演变 总被引:60,自引:5,他引:55
研究了未变质处理和变质处理的AZ91D镁合金在半固态等温热处理过程中的组织演变,并对其组织演变机理进行了探讨。结果表明:AZ91D镁合金在液-固相区570℃等温处理时,未变质处理的δ相由粗大的树枝晶演变为大块状,随后δ相发生熔化分离,并在半固态等温过程中演变为球状,产生相最小尺寸可达50-80μm;变质处理的初生δ相由等轴晶演变为小块状,随后进一步熔化分离为更细小的斑块,接着逐渐演变为球状组织,初生相最小尺寸可达20-60μm。等温处理时间过长时,两种组织都会发生合并长大。 相似文献
7.
胡勇 《稀有金属材料与工程》2016,45(2):493-497
研究了等温热处理对AZ91D+Ce镁合金半固态组织的影响,获得了较理想的球状或类球状晶粒组织。结果表明,在等温热处理的过程中,加入稀土Ce会阻碍原子向固相粒子聚集和结合,抑制固相颗粒的长大,形成细小圆整的半固态组织。随等温热处理温度的升高,原子活动能力增强,熔化速度加快,液相量增加,固相颗粒尺寸先减小后增大。在等温初始阶段,熔化对初生固相颗粒尺寸起决定作用,使得颗粒尺寸减小。但是,随等温时间的进一步增加,由于合并粗化和Ostwald熟化的作用,固相颗粒开始长大。 相似文献
8.
以AZ91D镁合金和平均颗粒尺寸为10μm和10 nm的SiC颗粒分别作为基体和增强相,通过半固态机械搅拌法制备出单、双尺寸SiC颗粒增强镁基复合材料。结果显示,SiCp体积分数为2%的10 nm SiCp/AZ91D复合材料的抗拉强度达到198 MPa,提升了34.7%,屈服强度达到113 MPa,提升了46.7%,伸长率达到6.4%,这主要由于纳米SiC颗粒的晶粒细化作用。断裂机制表明,SiCp/AZ91D复合材料裂纹主要沿微米SiCp-AZ91D的界面扩展。 相似文献
9.
新SIMA法制备AZ91D半固态坯 总被引:10,自引:11,他引:10
利用等径道角挤压试验、半固态等温处理试验、金相显微镜、SEM等试验方法和分析设备,对经过等径道角挤压的AZ91D镁合金在等温处理过程中的微观组织演变进行了研究。通过研究,提出了新SIMA制备AZ91D镁合金半固态坯方法。新SIMA法制备的半固态坯料的微观组织均匀,晶粒球化程度好,晶粒细小,平均晶粒尺寸在20—50μm之间。随着保温时间的延长,新SIMA法制备半固态坯料的微观组织有长大的现象,其可用Ostwald熟化理论描述。随着等温处理温度的升高,晶粒的尺寸先增加后减小,形状系数接近1。随着材料在ECAE中获得的等效应变的增加,半固态坯料的晶粒尺寸减小。 相似文献
10.
等温热处理工艺对AZ91D镁合金半固态组织演变和成形性的影响 总被引:32,自引:4,他引:32
研究了等温热处理温度和保温时间等工艺参数对AZ91D镁合金半固态组织演变和成形性的影响。结果表明 ,半固态等温热处理可以将普通金属型铸造的AZ91D镁合金锭中的枝晶组织转变为球形晶粒组织 ,其演变过程为 :在升温过程中晶界处部分γ相先发生溶解 ,随着温度的升高 ,剩余的γ相开始熔化 ,继而δ相也发生熔化 ,并在等温处理中逐渐演变为球状 ;保温温度越高 ,半固态重熔和δ相演变过程越快 ,保温温度过高或保温时间过长 ,试样易发生变形 ,同时 ,球状晶粒也容易趋于长大。AZ91D镁合金半固态成形所需的最佳工艺条件为加热温度 5 70℃左右 ,保温时间 2 5~ 35min ;或加热温度 5 80℃左右 ,保温时间 15~ 2 0min。 相似文献
11.
12.
K.B. Nie X.J. Wang K. WuL. Xu M.Y. ZhengX.S. Hu 《Journal of Alloys and Compounds》2011,509(35):8664-8669
Particulate reinforced magnesium matrix nanocomposites were fabricated by semisolid stirring assisted ultrasonic vibration. Compared with the as-cast AZ91 alloy, the grain size of matrix alloy in the SiCp/AZ91 nanocomposite stirring for 5 min was significantly decreased due to the addition of SiC nanoparticles. SiC nanoparticles within the grains exhibited homogeneous distribution although some SiC clusters still existed along the grain boundaries in the SiCp/AZ91 nanocomposite stirring for 5 min. With increasing the stirring time, agglomerates of SiC nanoparticles located along the grain boundaries increased. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite stirring for 5 min were simultaneously improved compared with the as-cast AZ91 alloy. However, the ultimate tensile strength and elongation to fracture of the SiCp/AZ91 nanocomposite decreased with increasing the stirring time. 相似文献
13.
1 INTRODUCTIONMagnesiumalloyshavefoundmoreandmoreus esintelecommunicationandtransportationindustriesduetotheirexcellentpropertiessuchashighstrengthtoweightradio ,goodconductivity ,appropriateelec tro magneticshieldingproperty .Howevertheircor rosionbehavi… 相似文献
14.
Particulate reinforced magnesium matrix nanocomposite prepared with semisolid stirring assisted ultrasonic vibration was subjected to extrusion at 350 °C with an extrusion ratio of 12:1. Extrusion of the SiCp/AZ91 nanocomposite induced large scale dynamic recrystallization resulting in a fine matrix microstructure. There were two kinds of zones in the extruded nanocomposite: SiC nanoparticle bands parallel to the extrusion direction and refined-grain zones between the SiC nanoparticle bands. In the SiC nanoparticle bands, there were SiC nanoparticles along the boundaries of refined grains. The distribution of SiC nanoparticles was uniform although some agglomerates of SiC nanoparticles still existed in the SiC nanoparticle bands. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite were simultaneously improved by extrusion. Results from the extruded SiCp/AZ91 nanocomposite tensile testing at different temperatures (75, 125, 175 and 225 °C) revealed an increase of the tensile strength and ductility values compared with the unreinforced and extruded AZ91 alloy. 相似文献
15.
The effects of pulsed magnetic field on the solidified microstructure of an AZ91D magnesium alloy were investigated. The experimental results show that the remarkable microstructural refinement is achieved when the pulsed magnetic field is applied in the solidification of AZ91D alloy. The average grain size of the as-cast microstructure of AZ91D alloy is refined to 104 μm. Besides the grain refinement, the morphology of the primary α-Mg is changed from dendritic to rosette, then to globular shape with changing the parameters of the pulsed magnetic field. The pulsed magnetic field causes melt convection during solidification, which makes the temperature of the whole melt homogenized, and produces an undercooling zone in front of the liquid/solid interface by the magnetic pressure, which makes the nucleation rate increased and big dendrites prohibited. In addition, primary α-Mg dendrites break into fine crystals, resulting in a refined solidification structure of the AZ91D alloy. The Joule heat effect induced in the melt also strengthens the grain refinement effect and spheroidization of dendrite arms. 相似文献
16.
17.
L. Zhang Y.B. Liu Z.Y. Cao Y.F. Zhang Q.Q. Zhang 《Journal of Materials Processing Technology》2009,209(2):792-797
The effects of isothermal process parameters on the microstructure evolution of semisolid AZ91D alloy produced by strain-induced melt activation (SIMA) were investigated using the self-programmed analysis software based on quantitative metallography. The results showed that long isothermal time could make the semisolid particles more globular, but the size of the particles would grow larger; high semisolid isothermal temperature would reduce the solid volume fraction and accelerate the spherical evolution of the solid particles. It was found that the optimal process parameters should be 570 °C and 10–20 min of isothermal temperature and time respectively based on the conditions of this paper. The mechanism of the particles’ formation was also discussed during the isothermal treatment. 相似文献
18.
19.
The corrosion performance of anodised magnesium and its alloys, such as commercial purity magnesium (CP-Mg) and high-purity magnesium (HP-Mg) ingots, magnesium alloy ingots of MEZ, ZE41, AM60 and AZ91D and diecast AM60 (AM60-DC) and AZ91D (AZ91D-DC) plates, was evaluated by salt spray and salt immersion testing. The corrosion resistance was in the sequential order: AZ91D ≈ AM60 ≈ MEZ ? AZ91D-DC ? AM60-DC > HP-Mg > ZE41 > CP-Mg. It was concluded the corrosion resistance of an anodised magnesium alloy was determined by the corrosion performance of the substrate alloy due to the porous coating formed on the substrate alloy acting as a simple corrosion barrier. 相似文献
20.
X. K. Suo Q. L. Suo W. Y. Li M. P. Planche H. L. Liao 《Journal of Thermal Spray Technology》2014,23(1-2):91-97
AZ91D/SiCp composite coatings were fabricated on AZ31 magnesium alloy substrates using cold spraying. The effects of SiC volume fraction and particle size on the deposition behavior, microhardness, and bonding strength of coatings were studied. The mean sizes of SiC particles tested were 4, 14, and 27 μm. The results show that fine SiC particles (d 0.5 = 4 μm) are difficult to be deposited due to the bow shock effect. The volume fraction of SiC particles in composite coatings increases with the increasing SiC particle size. The microhardness and bonding strength of composite coatings also show increases compared with AZ91D coatings. The volume fractions of SiC particles in the original powder were set at 15, 30, 45, and 60 vol.%. The corresponding contents in composite coatings are increased to 19, 27, 37, and 51 vol.%, respectively. The microhardness of composite coatings also increases as the volume fraction of SiC particles increases. 相似文献