Tensile properties of a Fe-32Mn-6Si shape memory alloy

The tensile properties of a Fe-32Mn-6Si shape memory alloy were investigated. It was found that tensile properties depend on temperature, heat treatment and material structure. The relationships of martensitic transformation, tensile properties, and shape memory effect are discussed. Finally, we propose a macroscopic one-dimensional constitutive law describing the thermomechanical behavior in tensile loading. Numerically obtained results are close to the experimental ones. __________ Translated from Problemy Prochnosti, No. 2, pp. 55–65, March–April, 2008.     

The effect of carbon on the high temperature oxidation of Fe-31 Mn-9Al-0.87C alloy

The alloy with the composition Fe-31Mn-9Al-0.87C was employed to investigate the effects of carbon on the oxidation behaviour at 800, 900 and 1000° C in dry air. Electron and optical microscopy were applied to examine the morphology and elemental redistribution in the oxide scale. Oxidation kinetics of the alloy oxidized at 800 and 900° C exhibited three-stage and two-stage parabolic rate laws, respectively. For the alloy oxidized at 1000° C, a carbon-induced breakaway three-stage oxidation mechanism developed. The carbon addition had a detrimental effect on the oxidation resistance and resulted in a porous initial oxide layer, which was favourable to the oxidation of manganese as well as the formation of a uniform and bulky oxide. As the oxidation temperature was increased, the diffusion rates of the metallic elements and the healing ability of oxide scales were enhanced. However, when the carbon content in alloy was above the saturation value, a breakaway scaling may have occurred due to the carbon-induced oxidation.     

Properties of electron-beam-welded and laser-welded austenitic Fe-28Mn-5Al-1C alloy

Austenitic Fe-28Mn-5Al-1C alloy was welded by electron-beam and CW CO₂ laser techniques. Tensile tests, impact tests, potentiodynamic and cyclic polarization measurements were used to evaluate the mechanical properties and corrosion behaviour of the weld materials, Metallographic examination showed that the microstructure of the electron-beam-welded and laser-welded metals consisted mainly of the columnar and equiaxed austenitic structures. Grain growth in the heat-affected zone (HAZ) was minimal for welding with these two techniques. The tensile and impact tests indicated that the weld materials exhibited lower tensile strength, percentage elongation, percentage reduction in area and impact energy than those of the base alloy. The polarization measurements revealed that the anodic polarization behaviour of the HAZs of the electron-beam-welded and laser-welded materials was identical to that of the base alloy when exposed in 1M Na₂SO₄ solution. However, the electron-beam-welded and laser-welded metals exhibited a higher current density in the passive region than that of the base alloy when exposed to 1N H₂SO₄ acid solution.     

Properties of austenitic Fe-25Mn-1Al-0.3C alloy for automotive structural applications

Austenitic Fe-25Mn-1Al-0.3C steel, cold-rolled and annealed at about 800 °C, exhibited 2.5 times higher tensile strength than current automotive ferritic sheet steel, while possessing comparable formability. The formation of strain-induced deformation twinning gave rise to an optimum combination of high strength and good formability.     

Ni-12Fe-1Mn-0.3Al和Ni-2.7Mn-1.7Al-1.1Si-0.8Co合金的热电特性

研究了有特殊要求的火警信号系统用Ni-12Fe-1Mn-0.3Al和ni-2.7Mn-1.7Al-1.1Si-0.8Co合金的热电特性,分析了合金化元素对热电特性的影响.     

The nitridation of austenitic Fe-29.8 Mn-7.4 Al-0.92 C and mainly ferritic Fe-32.3 Mn-8.8 Al-0.04 C alloys

The nitridation of the austenitic Fe-29.8% Mn-7.4% Al-0.92% C and mainly ferritic Fe-32.3% Mn-8.8% Al-0.04% C alloys was studied. Plate-shaped AIN was observed in both alloys after heating in air and nitrogen at 1000 C. The scale formed on Fe-Mn-Al alloy with prolonged heating in air at 1000 C consists of several layers, from the innermost layer are first, AIN with Al-depleted austenite matrix; second, AIN with manganese-depleted ferrite matrix; and third, intermixed oxide which was only observed on alloys heated in air. Mechanisms of the formation of AIN scale were discussed.     

Sr-Y复合变质对Al-7Si合金组织和性能的影响

为降低锶(Sr)变质Al-7Si合金熔体的含氢量和解决单添加稀土钇(Y)导致合金生产成本上升的问题,利用测氢仪、光学显微镜(OM)、扫描电镜(SEM)、WDW电子万能试验机和导电仪等测试手段,研究了 Sr-Y复合变质对Al-7Si合金微观组织和力学性能的影响规律并对其作用机制进行了分析探讨.结果表明,Sr-Y复合变质不...     

Effect of carbon on the oxidation of Fe-5.5 Al-0.55 C alloy

An alloy with the chemical composition Fe-5.5 wt% Al-0.55 wt% C is employed to investigate the effect of carbon on the oxidation at 600, 800 and 1000° C in dry air. Kinetic curves were determined by thermogravimetry analyses. Optical metallography and electron probe microanalysis were used to examine the oxide scales formed on the alloy surfaces. The kinetic curves observed at 600, 800 and 1000° C had simple, three-stage and two-stage parabolic rate laws, respectively. No carbide-free layer could be observed in the alloy which was oxidized at 600° C. In contrast, a carbide-free zone was found in specimens of the alloy after oxidizing at 800 and 1000°C.     

Section-dependent microstructure and mechanical properties of rapidly solidified and extruded Al-20Si alloy

The microstructure and mechanical properties of rapidly solidified and extruded Al-20Si alloys were studied by a combination of optical microscopy, scanning electron microscopy, X-ray diffraction, compression testing, and wear testing. The microstructure of the extruded bars showed a homogeneous distribution of different primary Si sizes and shapes embedded in the Al matrix depending on the section considered in the extruded bar. As the section changes from diagonal through perpendicular to parallel, the compressive yield strength increased from 219 through 225 to 263 MPa, respectively. The specific wear was the lowest at all sliding speeds for the parallel section in comparison to the perpendicular and diagonal sections of the extruded bar.     

The effect of exposure on the mechanical properties of the Ti-6Al-4v alloy

The mechanical properties of TJ-6A1-4V specimens were investigated after their exposure to air at 900°C. It was found that even short exposure causes a marked drop in ductility and decrease in the ultimate tensile strength, while the yield strength remains uneffected. The loss of ductility is attributed to small surface cracks which appear in the early stages of the tensile test along the entire gauge length of the specimens.     

Microstructure and internal friction of spray deposited Al-3.3Fe-10.7Si alloy

Al-3.3Fe-10.7Si alloy has been experimentally made with spray deposition technology. The internal friction of the alloy which was directly associated with the microstructures under spray deposited, extruted and heat treated conditions has been investigated using a low frequency inverted torsion pendulum over the temperature region of 10–300 °C. An internal friction peak was observed in the temperature range 50–250 °C in the present alloy. The Q^-1 peak decreased after extruted and in subsequent to the earliness of isothermal annealing, which was found to be directly attributed to the precipitation of FeAl₂ and Al– Fe– Si intermetallics from the supersaturated aluminium alloy matrix. We suggest that the internal friction peak in the alloy originates from grain boundary relaxation, but the grain boundary relaxation can also be affected by FeAl₂ and Al– Fe– Si intermetallics at the grain boundaries, which will impede grain boundary sliding.     

Pressure effect on the phase transformations and structure of an Al-12 at % Si alloy

Phase transformations of an Al-12 at % Si alloy have been studied by differential barothermal analysis at temperatures of up to 700°C in argon compressed to 100 MPa. Heating at a rate of 8°C/min under a pressure of 100 MPa has been shown to increase the temperature of the L → (Al) + Si eutectic transformation in the alloy by 4°C. After crystallization of the binary eutectic, the differential thermal analysis cooling curve showed an additional exothermic peak, corresponding to the decomposition of the aluminum-based solid solution (Al) at 547°C and precipitation of silicon particles in the nanometer range. A barothermal scanning cycle reduced numerical porosity characteristics of the alloy, except for the pore number density. The lattice parameter of silicon microparticles in the alloy approaches values in the literature, whereas that of nanoparticles is slightly greater. The lattice parameter of the aluminum remains unchanged during crystallization and cooling in compressed argon. The microhardness of the aluminum matrix of the alloy corresponds to that of pure aluminum.     

Microstructure and mechanical properties of Al-12Si and Al-3.5Cu-1.5Mg-1Si bimetal fabricated by selective laser melting

An Al-12 Si/Al-3.5 Cu-1.5 Mg-1 Si bimetal with a good interface was successfully produced by selective laser melting(SLM).The SLM bimetal exhibits four successive zones along the building direction:an Al-12 Si zone,an interfacial zone,a texture-strengthening zone and an Al-Cu-Mg-Si zone.The interfacial zone(<0.2 mm thick)displays an increasing size of the cells composed of eutectic Al-Si and a discontinuous cellular microstructure,resulting in the lowest hardness of the four zones.The texturestrengthening zone(around 0.3 mm thick)shows a remarkable variation of the hardness and<001>fiber texture.Electron backscatter diffraction analysis shows that the grains grow gradually from the interfacial zone to the Al-Cu-Mg-Si zone along the building direction.Additionally,a strong<001>fiber texture develops at the Al-Cu-Mg-Si side of the interfacial zone and disappears gradually along the building direction.The bimetal exhibits a room temperature yield strength of 267±10 MPa and an ultimate tensile strength of 369±15 MPa with elongation of 2.6±0.1%,revealing the potential of selective laser melting in manufacturing dissimilar materials.     

Effect of cerium and thermomechanical processing on microstructure and mechanical properties of Fe-10·5Al-0·8C alloy

The effect of cerium content and thermomechanical processing on structure and properties of Fe-10·5 wt.%Al-0·8 wt%C alloy has been investigated. Alloys were prepared by a combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR). The ESR ingots were hot-forged and hot-rolled at 1373 K as well as warm-rolled at 923 K and heat-treated. Hot-rolled, warm-rolled and heat treated alloys were examined using optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction to understand the microstructure of these alloys. The ternary, Fe-10·5 wt.%Al-0·8 wt.%C alloy showed the presence of two phases; Fe-Al with bcc structure, and large volume fraction of Fe₃AlC_0·5 precipitates. Addition of cerium to Fe-10·5 wt.%Al-0·8 wt.%C alloy resulted in three phases, the additional phase being small volume fraction of fine cerium oxy-carbide precipitates. Improvement in tensile elongation from 3–6·4% was achieved by increasing the cerium content from 0·01–0·2 wt.% and further improvement in tensile elongation from 6·4–10% was achieved by warm-rolling and heat treatment.     

Microstructure and mechanical properties of an indirect-extruded Mg-8Sn-1Al-1Zn alloy

The microstructure and mechanical properties of an indirect-extruded Mg-8Sn-1Al-1Zn (TAZ811) alloy were investigated and compared with those of a commercial Mg-3Al-1Zn (AZ31) alloy. In the extruded condition, the TAZ811 alloy shows a much smaller grain size but a stronger basal texture than the AZ31 alloy. In addition, the TAZ811 alloy contains fine Mg₂Sn particles in the microstructure, whereas the AZ31 alloy reveals relatively coarse and sparse Al-Mn particles. The TAZ811 alloy showed tensile and compressive strengthening as well as a reduction in yield asymmetry between tension and compression, which is mainly due to grain refinement and the presence of fine Mg₂Sn particles.     

Interface and fracture of carbon fibre reinforced Al-7 wt% Si alloy

The interface structure in an aluminium-7 wt% silicon alloy reinforced with carbon fibres has been investigated using analytical electron microscopy. Crystals of aluminium carbide (Al₄C₃) have been identified in interface regions and their structure and growth are discussed. Mechanical properties of the composite have been measured and fracture behaviour studied using acoustic emission analysis in parallel with microstructural examination. The results indicated that the aluminium carbide interfacial reaction had produced a strong fibre matrix bond, but reduced the fibre strength and embrittled the matrix. Consequently, whole fibre bundles failed in a brittle manner in the longitudinal direction with limited pull-out of individual fibres. The findings are discussed in relation to the method used to manufacture the composite.