纳米压痕法研究Si对Mg60Cu30Y10非晶合金的影响

利用纳米探针仪研究硅元素对Mg60Cu30Y10非晶合金的载荷-位移曲线和力学性能的影响。结果显示,Mg60Cu30-xY10Six非晶合金载荷-位移曲线上不连续锯齿状台阶对应其剪切带的形成和扩展。随着硅元素含量的增加,相同加载速率下,载荷-位移曲线上的台阶逐渐减少,直至消失。随着加载速率和应变速率的不断增加,非晶合金Mg60Cu30-xY10Six载荷-位移曲线上的锯齿状台阶逐渐消失。非晶合金Mg60Cu30-xY10Six的力学性能不是简单地随着组元的含量、数量等参数的增大而提高     

Effects of solute Mg on grain boundary and dislocation dynamics during nanoindentation of Al–Mg thin films

Using in situ nanoindentation in a transmission electron microscope (TEM) the indentation-induced plasticity in ultrafine-grained Al and Al–Mg thin films has been studied, together with conventional quantitative ex situ nanoindentations. Extensive grain boundary motion has been observed in pure Al, whereas Mg solutes effectively pin high-angle grain boundaries in the Al–Mg alloy films. The proposed mechanism for this pinning is a change in the atomic structure of the boundaries, possibly aided by solute drag on extrinsic grain boundary dislocations. The mobility of low-angle boundaries is not affected by the presence of Mg. Based on the direct observations of incipient plasticity in Al and Al–Mg, it was concluded that solute drag accounts for the absence of discrete strain bursts in indentation of Al–Mg.     

The microstructures of polycrystalline Al–0.1Mg after hot plane strain compression

The microstructures of Al–0.1Mg polycrystals deformed in plane strain compression at temperatures of 20–400 °C have been investigated by electron backscatter diffraction. At all temperatures, the microstructures are characterized by two types of banded substructure, primary bands of aligned low angle boundaries whose alignment to the rolling plane is a function of strain and temperature, and secondary bands which develop into grain-scale shear bands with increasing strain. Several aspects of the deformation microstructures, including the orientation dependence of subgrain parameters and the inhomogeneity of the microstructure, differ from those of single crystals of similar orientation, and this it attributed to local grain interactions.     

Bauschinger and size effects in thin-film plasticity

We present an experimental investigation of the effects of surface passivation, film thickness and grain size on the plastic behavior of freestanding Cu thin films. The stress–strain curves of the films are measured using the plane–strain bulge test. Films with a passivation layer on one or both surfaces have an offset yield stress that increases significantly with decreasing film thickness; the yield stress of unpassivated films, by contrast, is relatively independent of film thickness and increases mainly as a result of grain-size strengthening. The stress–strain curves of passivated films show an unusual Bauschinger effect on unloading. This effect is not observed for unpassivated films. Our experimental results suggest that passivation layers prevent dislocations from exiting the films and that they block slip bands at the film–passivation interface. The back stresses associated with these blocked slip bands increase the resistance to forward plastic flow on loading and cause reverse plastic flow on unloading. The effect of the back stresses increases with decreasing film thickness and leads to the observed strengthening of the passivated films. The constraint of a passivating layer on dislocation motion and hence on plastic flow cannot be described by classical plasticity theories, but can be modeled with some strain–gradient plasticity theories. We evaluate the suitability of the strain–gradient plasticity theory developed by Fleck and Hutchinson to describe our experimental results in a continuum framework. Comparison between experimental results and calculations yields very good agreement for the effect of film thickness, but the strain–gradient plasticity model fails to describe the Bauschinger effect observed in passivated films.     

Temperature Ranges of Phase Transformations and Mechanical Properties of Alloys of the Al - Cu - Mg - Ag System with Various Cu/Mg Ratios

The effect of the content of silver in the amount of 0.6 wt.% and of the Cu/Mg ratio in the range of 1.6 – 15 on the temperature ranges of phase transformations and on the properties of alloys of the Al - Cu - Mg - Ag system is studied with the aim of amending heat treatment modes. Pressed strips with cross section 10 × 100 mm are studied after natural and artificial aging. The method of differential scanning calorimetry is used to determine the temperature ranges and thermal effects in solid-phase dissolution (segregation) of excess phases and melting of the structural components. Mechanical properties are determined at room and elevated temperatures and the microstructure over the cross section of the strips is studied.__________Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 18 – 23, April, 2005.     

Singularities of the aging of alloys of the Al−Zn−Mg system

Conclusions Preliminary natural aging of Al–Zn–Mg alloys with Mn or Zr increases the strength after artificial aging; the lower the total concentration of zinc and magnesium and the lower the ZnMg ratio, the greater the degree of strengthening. The Al–Zn–Mg alloys with 4.8–5.3% Zn+Mg in which the ZnMg ratio is 1.5–2 and alloys with 6–6.5% Zn+Mg in which the ZnMg ratio is 1–0.9 are not strengthened during artificial aging without preliminary natural aging.N. A. Martynova, R. M. Sizova, and Yu. N. Kukushkin collaborated in the experimental part of this investigation.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 15–20, August, 1966.     

层状结构富Mg的Mg2Sn薄膜相组成与热电性能

利用高真空磁控溅射设备,通过顺序沉积制备富Mg的Mg2Sn热电薄膜。使用X射线衍射仪（XRD）、扫描电子显微镜（SEM）以及能谱仪（EDS）研究了沉积薄膜的物相组成、表面和截面形貌、元素含量及分布。使用塞贝克（Seebeck）系数/电阻分析系统LSR-3测量了沉积薄膜的电阻率和Seebeck系数,进而研究不同Mg含量的Mg2Sn薄膜的功率因子。结果表明,采用磁控溅射法可以制备出立方反萤石结构的Mg2Sn相薄膜,XRD显示,沉积薄膜是由立方结构的Mg2Sn相和少量的纳米尺寸的金属Mg相组成。随着Mg靶溅射时间的增加,纳米金属Mg相的含量增加,电阻率和Seebeck系数均表现为先升高后降低,这归因于少量纳米金属Mg相与基体相之间存在相界面。适量的金属Mg相存在于Mg2Sn薄膜中,有利于提高Seebeck系数。含有适量纳米尺寸金属Mg相的Mg2Sn沉积膜,因其Seebeck系数较高,电阻率适当,可获得较高的功率因子。层状结构的Mg2Sn薄膜可显著提高Seebeck系数,尽管电阻率也增加,但最终使薄膜的功率因子显著提高。     

Effect of hot and cold deformation on the P {0 1 1}4 5 5 recrystallization texture in a continuous cast Al–Mn–Mg aluminum alloy

The effect of different relative amounts of hot and cold deformation on the P {0 1 1}4 5 5 recrystallization texture in a continuous cast Al–Mn–Mg aluminum alloy was investigated by X-ray diffraction. The results show that at a given total rolling strain the sheet with a high hot rolling strain exhibits a significantly stronger P texture than the sheet with a low hot rolling strain. Hot deformation strongly promotes the formation of the P texture during recrystallization annealing.     

镁微合金化变形高温合金的蠕变行为

变形高温合金中加入适量Mg除能延长蠕变第二阶段,特别是第三阶段的时间外,还能降低低应变速率区的稳态蠕变速率,但在较高的应变速率时,影响不太明显。这种作用是晶内分布的Mg引起的。     

CREEP BEHAVIORS OF Mg MICROALLOYED WROUGHT SUPERALLOYS

By adding small amount of Mg to the wrought superalloys,the steady stage of creep,and es-pecially the tertiary stage of creep are prolonged.Also,the steady creep rate is decreasedwithin the range of low strain rates.At higher strain rates,however,the effect of Mg on creeprate vanishes.This may be attributed to the Mg dissolution in the matrix.A mechanism of theeffects of Mg addition on creep behaviors is proposed.     

Moderation of the recrystallization texture by nucleation at copper-type shear bands in Al-1Mg

The critical dependency of copper type shear band formation on deformation variables in Al-1Mg has been described (Acta mater., 49 (2001) 2739). The influence of copper type shear bands on recrystallization behaviour during post-deformation annealing in Al-1Mg is now discussed. Local orientation measurements and orientation images of grains nucleating at shear bands have been made using the electron back-scatter diffraction (EBSD) technique. Bulk recrystallization texture is investigated from X-ray diffraction (XRD) measurements. Shear bands are shown to be potent nucleation sites during annealing and a weak, almost random, texture associated with nucleation at shear bands has been inferred. Most significantly, shear band formation is found to have a pronounced moderating influence on the strength of the potentially dominant cube component of the recrystallization texture.     

Mg元素对热浸镀锌基合金镀层组织结构的影响

采用热浸镀方法在Q235钢板表面制备了Mg的质量分数分别为0.0%,0.1%,0.3%,0.5%的锌基合金镀层。利用扫描电子显微镜(SEM)、能谱仪(EDS)、辉光光谱仪(GDOES)等手段分析了Mg含量变化对镀层组织结构的影响。结果表明:随着镀层中Mg含量的增加,合金镀层的表面晶粒逐渐变小;Mg元素富集于晶界之中,起到细化晶粒的作用;Mg推迟了ζ相向δ相的转变,使镀层结构中的δ相层减薄。     

Deformation behavior of Al–1.5Mg processed using the equal channel angular pressing technique

Deformation behavior of submicron grain size Al–1.5Mg was studied using strain rate change tests. Compared to the annealed state, the strain rate sensitivity of the pressed materials increased, its peak shifted to lower temperatures and the dynamic strain aging regime at the lower temperatures was suppressed.     

Mg对初生Al3Fe形貌及其生长过程的影响

研究了Mg元素对铸造Al-10?过共晶合金初生Al3Fe相形态的影响.结果发现,加入Mg使初生Al3Fe相由原来的发达针状向树枝状→不规则块状转变.加Mg以前,初生Al3Fe相表面光滑,随着Mg加入量的增加,初生Al3Fe的分枝也逐渐加剧.对Mg元素的影响机理做了分析.     

稀土元素Nd对过共晶Mg-Si合金中Mg 2 Si粒子的变质作用

利用光学显微镜、扫描电镜及XRD物相分析研究稀土元素Nd对过共晶Mg-3%Si合金中Mg 2 Si粒子的变质作用与机理。结果表明：随着Nd含量的增加,初生Mg 2 Si粒子的形貌由粗大的树枝状转变为细小的多面体状。当Nd含量增至1.0%时,初生Mg 2 Si粒子被完全细化,尺寸约为10μm。然而,随着Nd含量的进一步增加,初生Mg 2 Si粒子反而又出现了粗化的现象。其变质机理主要是Nd元素富集于初生Mg 2 Si相的生长表面并抑制其优先生长晶向的生长,即中毒效应。当Nd含量超过3.0%时,初生Mg 2 Si粒子中的白色粒子由NdMg 2相转变为NdSi和NdSi 2化合物。因此,适量的Nd元素可以有效地细化初生Mg 2 Si粒子。     

铝合金脉冲激光焊Mg元素烧损行为及接头硬度分布

采用Nd:YAG脉冲激光对1mm厚5A05铝合金板进行焊接,结合激光焊物理过程,研究和分析了焊接工艺参数(脉冲能量、脉冲宽度、焊接速度和离焦量)对Mg元素烧损和焊缝熔深的影响,以及焊缝中Mg元素含量的变化和接头的硬度分布.结果表明,Mg元素烧损受熔池搅拌作用的影响,随搅拌作用增强和焊缝熔深的增加,焊缝中Mg元素烧损率减小;受Mg元素含量和冷却速度影响,焊接接头硬度在熔合线附近具有最大值,在焊缝中从表面到熔池底部硬度先减小再增大.     

Experimental study of the nonlinear internal friction peaks in Al–Mg solid solutions

Nonlinear internal friction peaks associated with the interaction between dislocations and point defects are experimentally studied in cold-worked Al–Mg solid solutions. It is found that the appearance of these peaks is very sensitive to the cold-work methods among which the stretching method in the strain range of several percent is effective for reproducing the peaks. A maximum of the internal friction vs. strain amplitude at a given temperature around the peak is observed. With the forced vibration method and by using a nonlinear fitting program to subtract the background, the activation energies are measured to be 1.3, 1.1 and 0.7 eV, respectively, for the three peaks (P_L1, P₁′, P₁″) in the order of ascending temperature.     

Theory of the nonlinear internal friction associated with bulk diffusion of solute atoms around dislocations in Al–Mg alloys

In this paper the nonlinear (amplitude-dependent) internal friction (P₃ peak) in cold-worked Al–Mg alloys is theoretically studied by solving the bulk diffusion equations of the solute atoms (Mg atoms) under the action of dislocation drag. The results in the case of a constant external stress show that the bow-out distance of the dislocation has an exponential relation with time, which can be well described by an exponential creep function with a Gaussian distribution in τ. With the increasing strain amplitude, the relaxation strength Δ and relaxation time τ decrease, while the distribution parameter increases. Both activation energy H and pre-exponential factor τ₀ deduced from τ through Arrhenius relation are dependent on strain amplitude.     

原位晶态相增强Mg-Cu-Dy非晶基块状复合材料

采用铜模喷铸法制备出直径为3 mm的原位Mg晶态相增强块状Mg70Cu17Dy13非晶基复合材料,对Mg-Cu-Dy类合金的力学性能和变形行为进行研究。结果表明,Mg70Cu17Dy13非晶基复合材料受压时产生加工硬化并获得最大抗压强度为702.38 MPa和塑性变形率为0.81%。这缘于其中Mg相有效的承载能力、塑性变形能力及Mg相对剪切带及裂纹扩展的有效抑制作用,可从其剪切变形、断裂方式和断裂面上密集的熔滴及凸凹不平得到证实     

电子束焊接5A06铝合金接头Mg元素蒸发烧损行为分析

研究了5A06铝合金电子束焊接后熔池内Mg元素的分布及其对焊缝硬度的影响,并分析了焊接工艺参数对Mg元素烧损行为的影响.结果表明,在接头区域随着熔深的增加,Mg元素含量增加,即烧损程度减小,同时显微硬度增大;随着加速电压和束流的增加,熔深增加,Mg元素烧损率降低;随着焊接速度增加,Mg元素烧损率降低,熔深却减小.为减小Mg元素烧损,在电子束焊时可适当增加焊接的加速电压与束流、加快焊接速度.