Mg在铸造Fe3Al合金中的行为及其对力学性能的影响

研究了Mg在Fe_3Al合金中的分布及其对力学性能的影响适量的Mg(0.002wt-%)明显改善Fe_3Al的室温和高温力学性能Auger分析表明,Mg偏聚在晶界TEM观察发现,适量Mg增加晶界协调晶内变形的能力,使位错易于穿过晶界继续滑移变形SEM观察表明,Fe_3Al合金室温下均呈穿晶解理特征,裂纹源在晶界上     

Deformation of nanocrystalline binary aluminum alloys with segregation of Mg,Co and Ti at grain boundaries

The influence of the temperature and sort of alloying element on the deformation of the nanocrystalline (NC) binary Al alloys with segregation of 10.2 at % Ti, Co, or Mg over grain boundaries has been studied using the molecular dynamics. The deformation behavior of the materials has been studied in detail by the simulation of the shear deformation of various Al bicrystals with the grain-boundary segregation of impurity atoms, namely, Ti, Co, or Mg. The deformation of bicrystals with different grain orientation has been studied. It has been found that Co introduction into grain boundaries of NC Al has a strengthening effect due to the deceleration of the grain-boundary migration (GBM) and difficulty in the grain-boundary sliding (GBS). The Mg segregation at the boundaries greatly impedes the GBM, but stimulates the development of the GBS. In the NC alloy of Al–Ti, the GBM occurs actively, and the flow-stress values are close to the values characteristic of pure Al.     

STUDIES OF Nb–TiAl ALLOY BY POSITRON ANNIHILATION TECHNIQUES

利用正电子湮没寿命谱(PALS)和符合Doppler展宽(CDB)技术研究了Ti51Al49合金中Nb的掺杂效应.结果表明:低含量掺杂时,Nb原子主要偏聚在合金晶界处,提高了晶界位置的自由电子密度,有利于改善合金的室温韧性;而较高含量的Nb掺杂时,由于形成了新的晶体结构,合金基体及晶界处的自由电子密度减少,导致合金的脆性增加.     

Gd对Mg9AlZnY镁合金消失模组织和性能的影响

在Mg9AlZnY合金基础上添加不同含量Gd元素,采用消失模铸造成形,研究其组织性能变化。结果发现,随着Gd含量的增加,Mg9AlZnY合金中的β-Mg17Al12相形成数量显著减少,并由连续网状结构转变为断续状和颗粒状结构。含Gd的Mg9AlZnY合金组织主要由α-Mg固溶体、β-Mg17Al12相和分布在α-Mg晶界的少量棒状Al2Y相和块状Al2Gd相组成。Al2Y和Al2Gd相热稳定性好,在高温下对晶界具有钉扎作用,防止晶界滑移,提高了晶界的高温强度。当Gd含量在0.9%(质量分数)左右时,经T6热处理后室温的抗拉强度为235MPa,200℃高温抗拉强度为156MPa,分别比Mg9AlZnY合金提高了11.9%和28.9%。     

定向凝固Ni3Al合金高温变形后的显微组织特征

利用金相,扫描电镜和透射电子显微镜研究了定向凝固Ｎｉ３Ａｌ合金高温变形后的显微组织特征。研究结果表明,当变形速率较快时,原始柱状晶晶界无明显变化,晶内无明显结构存在;当变形速率较慢,合金呈现塑变形时,变形初期柱状晶晶界呈现“锯齿状”,后期原始柱状晶界消失,代之以晶粒尺度约为１５ｍｍ的晶粒带,晶粒带中既有小角度晶界,也有大角度晶界。     

关于Fe－28Al合金中的析出相

用磁性分析、显微组织观察和Ｘ射线衍射对淬火态Ｆｅ—２８Ａｌ合金的结构进行了研究．结果表明，合金从Ｂ２区淬火后沿晶粒边界可有第二相析出，已初步确定它是Ｆｅ和Ａｌ的碳化物Ｆｅ_３ＡｌＣ_ｘ（ｋ相）．     

关于Fe—28Al合金中的析出相

用磁性分析、显微组织观察和Ｘ射线衍射对淬火态Ｆｅ—２８Ａｌ合金的结构进行了研究．结果表明，合金从Ｂ２区淬火后沿晶粒边界可有第二相析出，已初步确定它是Ｆｅ和Ａｌ的碳化物Ｆｅ_３ＡｌＣ_ｘ（ｋ相）．     

电刷镀技术对Fe3Al基合金室温环境脆性的改善作用

运用电刷镀技术在Ｆｅ３Ａｌ基合金表面刷镀一层Ｃｕ或Ｎｉ可以适度抑制其室温环境脆性，合金的室温塑性提高近３倍。ＳＥＭ分析发现，刷镀后在合金和镀层之间形成了过渡层，并在断口上出现了表征延性断裂的韧窝。     

两种含硼Ni3Al合金的微观组织与力学性能

本文研究了两种不同硼含量Ｎｉ３Ａｌ合金的微观组织、室温拉伸及高周疲劳性能，Ｎｉ３Ａｌ（０．６ａｔ．－％Ｂ）合金为单相组织，Ｎｉ３Ａｌ（１．０ａｔ．－％Ｂ）合金中除γ相外，还有微量共晶体，虽然Ｎｉ３Ａｌ（１．０Ｂ）的拉伸强度较Ｎｉ３Ａｌ（０．６Ｂ）的高，但在相同的循环应力水平下，后者的疲劳寿命显著高于前者的，疲劳断口观察表明两种合金的疲劳裂纹萌生和扩展行为各不相同。     

镁偏析对铝合金晶界性能影响的计算机模拟

采用嵌入原子法对铝晶界上Mg的偏析性质及其对晶界性能的影响进行了计算机模拟。结果表明 ,Mg的晶界偏析具有自发性 ,并且降低基体的电荷密度和空位形成能 ,从而导致晶界脆化。     

EFFECT OF Ce AND Cr ON ROOM TEMPERATURE MECHANICAL PROPERTIES OF Fe_3Al

Small amount addition of Ce to Fe_3Al results in a significant increase of room temperaturestrength of the alloy,and the combined addition of Ce and Cr improves both strength andductility.The fracture mode of Fe_3Al containing Ce is a mixed one of approximately 70%transgranular cleavage and 30% intergranular failure.In the deformed specimens of binaryFe_3Al the dislocations observed are mainly single dislocations with =(1/4)a_0~'〈111〉.However,a number of superlattice dislocations can be observed in the deformed specimens ofthe alloys with Cr addition.     

MICROSTRUCTURE OF MARTENSITE IN Cu-14Al-4Ni ALLOY AGED FOR A PROLONGED TIME AT ROOM TEMPERATURE

本文通过对室温时效二年的Cu-14Al-4Ni形状记忆合金进行电子显微研究,发现形状记忆合金中的马氏体在室温产生缓慢的亚结构变化,出现定向有序畴和晶界过渡区,孪晶界被破坏。矩形网格状有序畴产生并长大。首次观察到周期性反相结构与反相畴呈现在同一操作矢量下。用电子衍衬和能谱作原位观察,发现晶界出现溶质原子偏聚和位错缠结,晶内有序区出现周期性层错。基体、有序区和晶界的溶质原子Al的浓度呈现递增形式,其中基体贫Al,晶界富Al。     

Transformation mechanism of lamellar microstructure of AZ80 wrought Mg alloy during warm deformation

The microstructure especially the lamellar second phase evolution by a combination of deformation and heat treatment for AZ80 alloy was investigated.The results show that there are finer lamellar Mg_(17)Al_(12) phases after hot compression with the increasing strain,while there are coarse lamellar discontinuous precipitation cells ofβ-Mg_(17)Al_(12) phase spreading from the grain boundaries into the grains after T6 treatment of the compressed samples.The lamellar morphologies especially the lamellar dist...     

Fracture behaviors of AZ80 magnesium alloy during multiple forging processes

1 Introduction Pure magnesium and magnesium alloys are the lowest density metals used as structural materials and have excellent specific strength and stiffness, machinability, dimensional stability, and excellent recycling capability. They are, therefor…     

Microstructure and creep properties of Mg-4Al-2Sn-1 （Ca,Sr） alloys

The effects of Ca and Sr addition on the microstructure and creep properties of Mg-4Al-2Sn alloys were examined.Tensile tests at 25℃ and 200℃ and creep tests at 150℃ and 200℃ were carried out to estimate the room temperature and high temperature mechanical properties of these alloys.The microstructure of the Mg-4Al-2Sn alloy showed dendriticα-Mg,Mg17Al12 and Mg2Sn phases.The latter two phases precipitated along the grain boundaries.The addition of Ca and Sr resulted in the formation of ternary CaMgSn and SrMgSn phases within the grain.The grain size was reduced slightly with the addition of Sr and Ca.The tensile strength was decreased by the addition of Ca and Sr at room temperature.However,the high temperature tensile strength was increased.The creep strength was improved by the addition of Ca and Sr.     

Enhancing room temperature mechanical properties of Mg–9Al–Zn alloy by multi-pass equal channel angular extrusion

Influence of equal channel angular extrusion on room temperature mechanical properties of cast Mg–9Al–Zn alloy was investigated. The results show that room temperature mechanical properties of Mg–9Al–Zn alloy, such as yield strength, ultimate tensile strength and elongation, can be improved heavily by equal channel angular extrusion. Processing routes, processing temperature and extrusion passes have important influence on room temperature mechanical properties of processed Mg–9Al–Zn alloy by equal channel angular extrusion. The optimum room temperature mechanical properties such as yield strength of 209 MPa, ultimate tensile strength of 339 MPa and elongation of 14.1%, can be obtained when Mg–9Al–Zn alloy was processed by equal channel angular extrusion for 6 passes at route B_C at 498 K. Large bulk materials of Mg–9Al–Zn alloy with average grain size of 4 μm and high mechanical properties can be prepared.     

EFFECT OF Zr ON DUCTILITY OF CAST Ni_3 Al-BASE ALLOYS

Many compressive and tensile tests showed that the room temperature ductility of boron-freeNi_3Al alloy may be markedly improved by a moderate addition of Zr.The ductility of thestoichiometric Ni_3Al and even slightly enriched with Al,may be improved fairly between 400—600℃,which behaves much better if Zr is added together with B.However,the high tem-perature ductility of Ni_3Al alloys containing Cr may be significantly increased by Zr whichsegregates slightly along grain boundaries.Thus,the toughening mechanism of Zr alloyingseems to be different from that of B addition.     

Cr对Fe_3Al的韧化作用SCIEI

在Ｆｅ_３Ａｌ中添加适量的Ｃｒ使合金表面形成氧化膜时，可提高合金的常温延性。ＸＰＳ实验表明，这是由于在该氧化膜中有足够数量、致密的保护性氧化物Ａｌ_２Ｏ_３，可以抑制或推迟Ａｌ和环境水汽的反应，使材料的本征韧性得以充分发挥。     

EBSD技术研究Ni-48Al金属间化合物超塑变形组织演变

采用电子背散射衍射(EBSD)技术研究在1075℃、初始应变速率1.5×10-3s-1条件下大晶粒Ni-48Al合金超塑变形过程中的组织演变。结果表明,变形前,大晶粒Ni-48Al合金以大角度晶界为主,小角度晶界比例极低。在超塑变形过程中,持续有取向差≤5°的小角度晶界产生。随变形量的增大,新形成的小角度晶界取向差增加,转变为取向差6°~15°小角度晶界,进而转变为取向差>15°的大角度晶界。小角度晶界的产生速率与小角度晶界转变为较大角度晶界的速率趋向一动态平衡。小角度晶界向较大角度晶界不断转变的结果使大角度晶界数量不断增加,最终导致晶粒显著细化。     

微量Sc和Zr对Al—Mg合金铸态组织的晶粒细化作用

制备了Ａｌ５Ｍｇ、Ａｌ５Ｍｇ０．２Ｓｃ、Ａｌ５Ｍｇ０．１Ｚｒ和Ａｌ５Ｍｇ０．２Ｓｃ０．１Ｚｒ四种铸态合金，采用金相显微镜和扫描电镜观察分析了微量Ｓｃ和Ｚｒ对ＡｌＭｇ合金铸态组织的晶粒细化作用及其机理。结果发现，０２％的Ｓｃ并未使ＡｌＭｇ合金产生晶粒细化作用，而０２％的Ｓｃ与０１％的Ｚｒ复合添加则使ＡｌＭｇ合金产生了极其强烈的晶粒细化作用。这一作用的产生，是由于Ｓｃ、Ｚｒ与Ａｌ在合金熔体中生成了Ａｌ３Ｓｃ和Ａｌ３Ｚｒ复合粒子，这种粒子在合金凝固过程中，起到了非均质晶核细化晶粒的作用