能量色散X射线荧光分析基本参数法研究

本文介绍了EDXRF中基本参数法原理和计算方法,基于此方法用C语言设计编写了基本参数法的计算程序。通过配制的合金样用该法测定其成分含量,结果表明所测合金样的成分含量与其化学分析结果基本上一致,精确度较高,相对标准偏差不超过1.3%。

Temperature variation and solution treatment of high strength AA7050

Temperature variation and solution treatment of high strength aluminum alloy were investigated with temperature data acquisition system,microstructural observation,mechanical properties test,electrical conductivity measurement and differential scanning calorimetry（DSC） analysis.Specimens with two dimensions were employed in the experiment.The results indicate that the specimens with large size undergo low solution temperature and short time,giving rise to the reduction of hardening precipitates.The optimized solution treatments for specimens with dimensions of 25 mm×25 mm×2.5 mm and 70 mm×60 mm×20 mm are（480 ℃,30 min） and（480 ℃,90 min）,respectively.The densities of GP zones and η＇ phases of the small specimen are higher than those of the large specimen,which is consistent with the properties of the alloys.

INVESTIGATION OF FOAM-METAL INTERFACE BEHAVIORS DURING MOLD FILLING OF MAGNESIUM ALLOY LFC PROCESS

The visual observation of the mold filling and the standard analysis-of-variance （ANOVA） for the velocity of the filling metal are conducted to study foam-metal interface behaviors during the mold filling of the lost foam casting （LFC） process of the magnesium alloy. Results show that the foam primarily melts into liquid products instead of gasifying at the pouring temperature of the magnesium alloy. Without the vacuum, the metal fills smoothly with a slightly convex metal front, and the velocity of the filling metal is low and continually decreases as the foam is displaced. The mold filling is governed by the removal of foam decomposition products at the foam-metal interface. However, when the vacuum is applied, the mold filling is controlled by the foam decomposition rate at the foam-metal interface. A pronounced irregular and concave metal front is formed. The velocity of the metal front varies tremendously during the mold filling process and is ruleless. The metal velocity increases rapidly, and the vacuum shows a strong interaction effect with the pouring temperature on the metal velocity. As the vacuum continues to increase, the pouring temperature becomes the most significant factor for the mold filling, while both the vacuum effect and the interaction effect between the vacuum and the pouring temperature on the metal velocity are substantially reduced. Based on experimental results, a model for the foam thermal degradation and the removal of decomposition products occurred at the foam-metal interface is presented during the mold filling of the magnesium alloy LFC process under the vacuum.

Hot-compression behavior of Al-1Mn-1Mg alloy

The hot-compression of Al-IMn-IMg （mass fraction, %） alloy sample was carried out on a Gleeble-1500 thermo-simulator at deformation temperatures from 320 to 400 ℃ and strain rates from 0.1 to 10 s 1 by total strain of 1.4. Microstructure and texture evolution of the hot-compressed alloy were investigated by optical microscopy and X-ray diffraction analysis, respectively. The results show that the relationship among flow stress a, deformation temperature T and strain rate ε can be expressed in the form of βσ = lnε＋Q/（RT）-lnA. The threshold value of In Z （Z is Zener-Hollomon parameter） characterizing the dynamic recrystallization （DRX） is 46, below which the DRX takes place. A strong P orientation {011}（455） associated with a weak cube orientation { 100} （001） is found in the recrystallized sample during hot-compression.

Morphology observation for surface orange peel and fracture in tension sample of aluminum-alloy sheet and characterization of nano hardness

The tension property of aluminum-alloy sheet with different microstructures is measured, and the surface and tension fracture morphology of tension sample with and without orange peel are observed by using scanning electron microscope （SEM）. Surface roughness and nano hardness of tension sample are measured. The results show that the average elongation of the samples with orange peel is lower than that without orange peel ; especially the r value of per- pendicular to the rolling direction is much lower than that without orange peel. The tension surface of the orange peel samples is very rough; various parameters of surface roughness are higher. Under the observation of SEM, a wider slid- ing band with a micro crack on the surface of orange peel sample can be found. The various parameters of surface rough- ness without orange peel sample are near to zero, the sliding band is narrow and without micro cracks. The dimple width in tensile fracture of orange peel sample is larger than that without orange peel sample, but shear lip is narrower. The nano hardness testing results show that samples with orange peel behave high elastic modulus, high hardness, and high maximum load, but low plastic deformation depth. These mentioned features can completely describe surface and frac- ture morphology of tension samt31es with oranze peel.

Nonisothermal Crystallization Kinetics of Poly(phenylene sulfide)/Poly(ethylene-co-cyclohexane 1,4-dimethanol terephthalate) Blend

Binary alloy samples consisting of poly（phenylene sulfide） （PPS）/poly（ethylene terephthalate-co-cyclohexane 1,4-dimethanol terephthalate） （PETG） blend were prepared by the melt blending technology using a twin-screw extruder. The nonisothermal crystallization kinetics of binary alloys made of poly（phenylene sulfide） （PPS） and poly（ethyleneco-cyclohexane 1,4-dimethanol terephthalate） （PETG） was studied by the differential scanning calorimetry （DSC） at different cooling rates. The test results revealed that the addition of PETG could shift the crystallization temperature of PPS toward the high-temperature direction. The nonisothermal crystallization kinetic parameters of the PPS/PETG alloy samples were calculated by the methods proposed by Avrami and Mo. Test results demonstrated that the PPS/PETG alloy could give birth to apparent secondary crystallization. The value of Avrami exponent was lower relatively, while Mo＇s method was more suited to the nonisothermal crystallization process of the PPS/PETG alloy.

Fracture strength evaluation of titanium alloys using modified average stress criterion

Structural integrity procedures were used to demonstrate the fitness for the purpose of engineering components transmitting loads. The prediction of the fracture strength of titanium alloys containing sharp notches through the damage model depends on the un-notched strength and the critical length of the damage zone ahead of the notch. In general, the critical length of the damage zone depends on the material, specimen, and size of the sharp notch. Modifications were made in one of the stress fracture criteria known as the average stress criterion for accurate prediction of notched tensile strength of titanium alloy specimen containing sharp notches. To examine the adequacy of these modifications, fracture data of center-cracked titanium alloys with various thicknesses are considered. The notched （fracture） strength estimates are found to be close to the test results. The modified average stress criterion is very simple to predict the notched tensile strength.

Measurement of Refractive Index of Liquid-state Alloy SCN-Eth by Laser Interference

The method to measure the refractive index of the liquid-state metal is introduced. By inserting a wedge sample cell to the optical path of the Michelson interferometer, the refractive index of the liquid-state alloy SCN-Eth is measured at different temperatures and densities. The results show that this method can be applied to measure the refractive index of various liquids, especially at different temperatures.

The temperature dependence of optical properties of InGaN alloys

In our experiments,the PL spectra of several In x Ga 1 x N alloy samples with In contents x=0.1,0.15 and 0.25 were measured as a function of temperature ranging from 10 K to 300 K.S-shaped temperature dependencies were observed in all InGaN samples and a sharp decrease in the full width at half maximum occurred with decreasing temperature in the moderate temperature region.It was found that both phenomena are relative to localization effects.In addition,the degree of localization effects in three samples was investigated using the band-tail model.Our findings are presented in this paper.

A research study on the spallation strength of LY12 aluminum under the pre-compression condition

To pre-compress the disk-shaped LY12 samples along the radial direction can be done with the aid of overstress assembly by heating or by mechanical clamping, which can also generate the deviatoric stress fields under different states. The spallation signals of these pre-compressed samples are measured by VISAR in the light-gas gun shock experiments. The experimental results show that even under the same impact velocity, the pullback amplitudes of the velocity at the free surface of the sam- pies vary significantly. According to the experimental data, we propose a distinct concept that the material spallation strength is closely related to the deviatoric stress fields in the material. Based on the numerical simulation, we develop a damage con- stitutive model, which reveals that the deviatoric stress reduces the tensile threshold of the void growth. The numerical inves- tigations also demonstrate that the spallation strength decreases as pre-compression increases. The experimental idea proposed in this paper can also be used to study the spallation process in other structures.

Effect of thermal cycling on the mechanical properties of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) alloy

The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated.The metallic glassy samples are sealed into quartz tubes under high vacuum condition,and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between 196℃ and 150℃.The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis,mechanical properties measurement and thermal analysis.It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles,which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.