机械振动对铸造铝合金组织与性能的影响

在AlSi10Mg铸造铝合金凝固过程中施加不同的机械振动幅度和机械振动频率的振动处理,研究了机械振动参数对AlSi10Mg合金组织和力学性能的影响。结果表明,随着机械振幅的增加,合金的抗拉强度和断后伸长率呈现先增加而后降低的趋势,在机械振幅为0.11mm时取得最大值;随着机械振动频率的增加,合金的抗拉强度和断后伸长率呈现先增加而后降低的趋势,在机械振动频率为36Hz时取得最大值;AlSi10Mg合金在凝固过程中的适宜的机械振动参数为:机械振幅为0.11mm、机械振动频率为36Hz。机械振动改善AlSi10Mg铸造铝合金的强度和塑性主要与合金的组织均匀性和晶粒细化有关。     

机械振动对A356合金组织与性能的影响

通过在A356合金充型和凝固过程中施加机械振动,研究了机械振动参数对合金组织和力学性能的影响。结果表明,对A356合金施加机械振动,有助于气孔向冒口移动,可以减少合金中的气孔数量;随着振动频率增加,合金的抗拉强度和伸长率都呈现先增加后降低的趋势,在振动频率为30Hz时取得最大值;随着机械振幅的增加,合金的抗拉强度和伸长率都呈现先增加后降低的趋势,在振幅为0.3mm时取得最大值;随着振动方向角的增加,合金的抗拉强度和伸长率都表现为逐渐降低的趋势。A356合金适宜的机械振动参数如下:频率为30Hz、幅度为0.3mm、方向角为90°。     

机械振动对消失模铸造铝合金组织与性能的影响

研究了机械振动对消失模铸造AlSi9Mg合金组织与性能的影响,并分析了其作用机理。结果表明,Z方向机械振动的AlSi9Mg合金的平均晶粒尺寸最小,布氏硬度、抗拉强度和伸长率最大,其次为XY方向,而X、XZ和XYZ方向振动的AlSi9Mg合金的平均晶粒尺寸稍大,布氏硬度、抗拉强度和伸长率相对较小。随着机械振幅或振动频率的增加,AlSi9Mg合金的平均晶粒尺寸呈现先减小而后增加的趋势,而布氏硬度、抗拉强度和伸长率都呈现为先增加而后降低的趋势。消失模铸造AlSi9Mg合金适宜的机械振动工艺:机械振动方向为Z向,机械振幅为0.10mm,机械振动频率为36 Hz,在此工艺下可以获得较好的强度与塑性。     

机械振动对Q690钢焊接接头组织与性能的影响

在Q690钢熔化极活性气体保护焊过程中施加机械振动,研究了机械振幅和振动频率对Q690钢焊接接头力学性能的影响,并对断口形貌进行了观察。结果表明,固定振动频率,焊接接头试样的抗拉强度、断后伸长率、断面收缩率和冲击功都随着振动幅度的增加先增加而后减小,在振幅为0.04 mm时取得最大值,无振动和施加机械振动的焊接接头的拉伸断裂位置都位于焊缝处;振幅为0.02～0.06 mm时,冲击断口呈现韧性断裂特征,而振幅0.08 mm时冲击断口为脆性断口。固定振幅,焊接接头试样的抗拉强度、断后伸长率、断面收缩率和冲击功都随着振动频率增加而降低,振动频率为25Hz时的强塑性和冲击功高于无振动焊接接头,而振动频率为35、45和55 Hz时的强塑性和冲击功都小于无振动焊接接头;振动频率为25～45 Hz时的冲击断口为韧性断口,而55 Hz时的断口呈脆性断裂特征。     

机械振动对A356合金组织与力学性能的影响

通过改变机械振动频率、振幅和振动角度,考察了不同机械振动参数对A356合金的组织与力学性能的影响。结果表明,当振动频率为20~30Hz、振幅为0.3~0.6mm,机械振动角度为0°时,A356合金中的初生α-Al相和二次枝晶细小,A356合金可以取得理想的强度和塑性结合。     

振动频率与振幅对A356铝合金组织和性能的影响

主要研究了机械振动铸造过程中不同的振动频率和振幅对A356铝合金的微观组织和力学性能的影响。结果表明:试样的晶粒尺寸大小、抗拉强度和伸长率随着振动频率和振幅的增加先升高后降低;当振动频率为30 Hz、幅度为0.6 mm时,A356铝合金试样的综合力学性能最好。     

机械振动对ADC12铝合金消失模铸件性能影响研究

以消失模铸造铸造ADC12铝合金为对象,研究不同机械振动条件对铝合金性能的影响。结果发现,随机械振动峰值加速度的增加,铝合金液产生对流现象并引发枝晶破碎,形核数量不断增加,晶粒逐渐细化;合金抗拉强度随着振动频率、振幅的增加而增大,在振动频率为100 Hz、振幅为0.08 mm时达到最大值,但随着振动频率、振幅的进一步增加,合金抗拉强度开始逐渐下降。     

计算机嵌入式系统在HQ100钢焊接中的应用

将计算机嵌入式系统成功应用到高强钢板的焊接程中,通过控制焊接工艺参数,研究了机械振动振幅、振动频率对HQ100钢GMAW焊接接头力学性能的影响规律。结果表明,随着振动振幅的增加,焊接接头的抗拉强度、伸长率、断面收缩率和冲击功都表现为先增加而后减小,在振幅为0.04 mm时取得最大值;随着振动频率的增加,焊接接头的抗拉强度、伸长率、断面收缩率和冲击功逐渐降低,且只有在振动频率为20 Hz时焊缝的冲击韧性有所改善。     

搅拌铸造对汽车空调压缩机轴用20CrVCe钢性能的影响

利用不同工艺铸造了汽车空调压缩机轴用新型20Cr VCe钢试样,并进行了试样的力学性能和磨损性能的测试与分析。结果表明:搅拌铸造能显著提高试样的强度和磨损性能。随浇注时机械振动频率的增大,试样的强度和磨损性能均先提高后下降。与常规铸造相比,采用40 Hz机械振动频率的搅拌铸造,试样的抗拉强度增大40 MPa,屈服强度增大44 MPa,断后伸长率减小0.5%,磨损体积减小13.2×10~(-3)mm~3。铸造工艺优选为:浇注时40 Hz机械振动频率的搅拌铸造。     

机械振动参数对ZL205合金凝固行为的影响

采用四因素三水平的正交实验法,研究了模数比、机械振动频率、机械振幅和起振温度对ZL205合金凝固补缩和致密度的影响,并分析了其作用机理。结果表明,四种机械振动参数中对缩孔体积影响从大至小依次为:模数比>机械振动幅度>起振温度>机械振动频率;四种机械振动参数中对致密度影响从大至小依次为:模数比>机械振动频率>起振温度>机械振动幅度。为了获得最小缩孔体积的铸造工艺参数为:振动频率15 Hz、振幅0.8 mm、模数比1.25、起振温度为610℃;为了获得最佳致密度的铸造工艺为:振动频率25 Hz、振幅0.8 mm、模数比1.25、起振温度为650℃。     

金刚石膜机械和机械-化学抛光

化学气相沉积(CVD)法生成的金刚石膜具有天然金刚石的基本性质，在机械、电子、光学等领域都有着广泛的应用。但CVD金刚石多晶膜表面凹凸不平，表面粗糙度较大，限制了它的广泛应用，因此，金刚石膜的抛光成为必不可少的工艺步骤。但是，金刚石膜的硬度非常高，且厚度薄，整体强度低，易破裂或剥落，抛光难度很大。国内外学者通过实验和研究，提出了多种金刚石膜抛光的理论和方法。本文详细论述了几种典型的机械、化学、机械-化学抛光方法的机理、工艺和特点。     

Mechanical Alloying

This paper reviews state-of-the-art mechanical alloying (MA) technology, a technique which is being used to produce attractive property combinations in nickel- and aluminum-base materials. Other applications include coatings, supercorroding alloys and, to a minor extent, production of normally difficult to produce alloy combinations. Even though mechanical alloying is already a commercially viable process for producing materials with enhanced behavior, many facets of this processing approach are still in the embryonic stage and warrant more indepth exploration.     

机械振动对铸造镁合金组织和力学性能的影响

本文研究了低频振动对镁合金AZ91D组织和力学性能的影响。实验结果表明,在镁合金AZ91D凝固过程中施加机械振动能有效的细化合金组织,且振动频率越高组织细化越明显。同时机械振动又能显著提高AZ91D的力学性能,最大抗拉强度和伸长率比铸态的提高了17.8%和20.09%。     

Mechanical spectroscopy of quasicrystals

Quasicrystals are solids with long-range quasiperiodic order and orientational order with disallowed crystallographic symmetry (e.g. 5-fold). In addition to the point defects known from crystals (vacancies, interstitials, or antistructure atoms) quasicrystals contain phasonic defects (phasons), which represent violations of the matching rules. Phasons allow displacement of atoms without contribution of vacancies. In icosahedral AlPdMn single quasicrystals two internal friction peaks are observed. Peak A at 370 K (f=3 Hz) has an activation enthalpy of 0.98 eV and a frequency factor close to the Debye frequency (2×10¹⁵ s⁻¹) and is therefore attributed to point defects, i.e. atomic jumps enabled by phason flips or vacancies. Peak B at 870 K (f=3 Hz) is determined by an activation enthalpy of 4 eV and an abnormal high frequency factor (3×10²⁴ s⁻¹), is much broader than a simple Debye-peak, and highly asymmetric. The temperature variation of the relaxation time exhibits significant deviation from ideal Arrhenius behaviour for higher temperatures (T>920 K) indicating a sort of phase transition. Peak B can be attributed to a relaxation process in which dislocation movement is controlled by creation and movement of phason defects.     

Mechanical properties of polyaniline

In spite of extensive electrical characterization of polyaniline, the information on its mechanical properties is missing in the literature. Complex Young's modulus of polyaniline compressed into pellets was measured at room temperature and an influence of preparation conditions of the polyaniline pellets on mechanical properties was studied. Young's modulus of PANI hydrochloride pellets was 0.9 ± 0.2 GPa and that of polyaniline base 1.3 ± 0.2 GPa. These values are comparable with common polymers, such as bulk polystyrene, 1.8 ± 0.1 GPa, or compressed polystyrene powder, 0.80 ± 0.02 GPa. Modulus of polyaniline is independent of the compression pressure above 300 MPa, the time of compression had no effect.     

Non-Linear Mechanical Behavior of Plasma Sprayed Alumina Under Mechanical and Thermal Loading

Mechanical response of plasma sprayed ceramic coatings to mechanical and thermal loading of various extents was studied. Coated samples were subjected to four-point bending (4PB), with coatings loaded in tension and compression, respectively. Thermal loading was provided by heating the samples, while stresses were generated by thermal mismatch between the coatings and substrates. In both cases, cyclic loading was applied. Non-linear behavior and significant hysteresis were observed, indicating inelastic phenomena taking place. The tests were complemented by structural observations in SEM and indentation tests. Relevant structural features and possible mechanisms underlying this behavior are discussed.     

Microstructure and Mechanical Property of Ni Metal Treated by Surface Mechanical Attrition

A nanostructured surface layer can be formed in Ni metal treated by surface mechanical attrition (SMA). The microstructure was investigated by using optical microscope, X-ray diffractometer and transmission electron microscope,respectively. Mechanical property measurements indicate that the yield strength of the surface layer raises significantly while the tensile strength somewhat changes and the elongation percentage reduces severely compared with that of the inside layer. Meanwhile, yield-drop-like phenomenon occurs in the surface layer after SMA treatment. In order to compare the mechanical behavior of nanostructured materials with two phases, Fe-30Ni nanostructured alloy was also investigated.     

力学探针及其在薄膜力学性能测量上的应用

力学探针是近年来发展的一种先进的微区力学性能测试方法。本文介绍了力学探讨的工作原理，以及采用力学探针技术准确测量薄膜力学性能的两步压入法，展示了这种测试技术在材料力学性能评价上的明显优势和发展潜力。