共查询到20条相似文献,搜索用时 15 毫秒
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I. A. Borisov 《Metal Science and Heat Treatment》1991,33(11):828-832
1. | We worked out a mathematical model of the change of strength properties of Cr–Ni–Mo–V steels during lengthy tempering (up to 1000 h). |
2. | The limiting degree of loss of strength of Cr–Ni–Mo–V steels in lengthy tempering depends on the initial structure. Steels with initial bainitic structure lose strength to 0.2=430–470 N/mm2, with pearlitic-bainitic structure to 0.2=320–N/mm2. |
3. | The change of impact toughness and of the semi-brittle point with longer tempering times is due to processes of polygonization and recrystallization of the -phase, and also to carbide transformations in tempering. |
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Yu. V. Efimov L. N. Snigir' G. G. Mukhin V. N. Dmitriev 《Metal Science and Heat Treatment》1988,30(12):903-907
1. | Increased silicon and boron content of amorphous alloys with 15–30% (B+Si) causes a rise of the crystallization temperature, and consequently, greater stability of the metastable state. |
2. | The principal phase in the crystallization of amorphous alloys of the system Fe–Si–B is -ferrite. As a rule, the crystallization of amorphous alloys proceeds in several stages and ends with the formation of a mixture of -ferrite and the metastable binary phases Fe3Si; Fe3B; Fe26B6. Ternary and binary equilibrium compounds form solely after lengthy annealing. |
3. | When rapidly quenched alloys are heat-treated, highly disperse structures form. A fine-grained structure and correspondingly high microhardness are retained within wide ranges of temperatures and holding times. |
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《中国有色金属学会会刊》2021,31(7):1951-1968
The microstructure and properties of the as-cast, as-homogenized and as-extruded Mg−6Zn−4Sn−1Mn (ZTM641) alloy with various Al contents (0, 0.5, 1, 2, 3 and 4 wt.%) were investigated by OM, XRD, DSC, SEM, TEM and uniaxial tensile tests. The results show that when the Al content is not higher than 0.5%, the alloys are mainly composed of α-Mg, Mg2Sn, Al8Mn5 and Mg7Zn3 phases. When the Al content is higher than 0.5%, the alloys mainly consist of α-Mg, Mg2Sn, MgZn, Mg32(Al,Zn)49, Al2Mg5Zn2, Al11Mn4 and Al8Mn5 phases. A small amount of Al (≤1%) can increase the proportion of fine dynamic recrystallized (DRXed) grains during hot-extrusion process. The room- temperature tensile test results show that the ZTM641−1Al alloy has the best comprehensive mechanical properties, in which the ultimate tensile strength is 332 MPa, yield strength is 221 MPa and the elongation is 15%. Elevated- temperature tensile test results at 150 and 200 °C show that ZTM641−2Al alloy has the best comprehensive mechanical properties. 相似文献
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Evaluations of austenite fraction and transformation kinetics upon intercritical annealing of low carbon TRIP steels were
attempted using quantitative dilatometric analysis. The measured dilation curves were analyzed by taking the carbon distribution
between austenite and its decomposed phases into account. The amount of austenite formed during intercritical annealing and
its carbon content obtained by dilatometric measurement was compared with the values predicted by thermodynamic calculations
under the ortho-equilibrium and para-equilibrium conditions. The kinetics of the reaustenization process including pearlite
dissolution and non-isothermal and isothermal formation of austenite could be quantitatively characterized by means of a modified
JMAK (Johnson-Mehl-Avrami-Kolmogrov) equation. 相似文献
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Hydrogen permeability of Pd-coated Ni60Nb15Ti15Zr10 and Ni60Nb20Ti15Zr5 amorphous alloys was measured in the temperature range of 673 K to 773 K and was compared with the results obtained using
Ni60Nb40, a binary amorphous alloy. The permeability thus measured was found to increase moderately increasing temperature. A long-term
permeation test for the Pd-coated Ni60Nb15Ti15Zr10 amorphous alloy revealed high permeation stability up to 16.6 h. 相似文献
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《中国有色金属学会会刊》2021,31(12):3626-3642
Effects of welding speed on the microstructure evolution in the stir zone (SZ) and mechanical properties of the friction stir welding (FSW) joints were studied by OM, XRD, SEM, TEM, EBSD and tensile testing. Compared with the base metal (BM), an obviously fine dynamic recrystallization (DRX) microstructure occurs in the SZ and the DRX grain size decreases from 5.6 to 4.4 μm with the increasing of welding speed. Fine DRX microstructure is mainly achieved by continuous dynamic recrystallization (CDRX) mechanism, strain induced boundary migration (SIBM) mechanism and particle stimulated nucleation (PSN) mechanism. Meanwhile, the geometric coalescence and the Burke−Turnbull mechanism are the main DRX grain growth mechanisms. Among all the welding speeds, the joint welded at rotation speed of 1500 r/min and welding speed of 75 mm/min has the greatest tensile properties, i.e. ultimate tensile strength (UTS) of (509±2) MPa, yield strength (YS) of (282±4) MPa, elongation (El) of (23±1)%, and the joint efficiency of 73%. 相似文献
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《中国有色金属学会会刊》2020,30(9):2459-2471
Taking a Ti−5Al−5Mo−5V−1Cr−1Fe alloy as exemplary case, the fatigue crack growth sensitivity and fracture features with various tailored α phase morphologies were thoroughly investigated using fatigue crack growth rate (FCGR) test, optical microscopy (OM) and scanning electron microscopy (SEM). The tailored microstructures by heat treatments include the fine and coarse secondary α phase, as well as the widmanstatten and basket weave features. The sample with coarse secondary α phase exhibits better comprehensive properties of good crack propagation resistance (with long Paris regime ranging from 15 to 60 MPa·m1/2), high yield strength (1113 MPa) and ultimate strength (1150 MPa), and good elongation (11.6%). The good crack propagation resistance can be attributed to crack deflection, long secondary crack, and tortuous crack path induced by coarse secondary α phase. 相似文献
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《中国有色金属学会会刊》2022,32(3):838-849
The effects of Li content on the microstructure and mechanical properties of the as-cast Mg?xLi?3Al?2Zn? 0.5Y (LAZx32-0.5Y) alloys were investigated by XRD, SEM, TEM, hardness tester and universal testing machine. The results show that the matrix of the alloy transforms from α-Mg to α-Mg+β-Li and then to β-Li when the Li content increases from 4% to 14% (mass fraction). All LAZx32-0.5Y alloys contain AlLi and Al2Y, while MgLi2Al appears only in the alloy containing the β-Li matrix. As the Li content increases, the content of AlLi and MgLi2Al gradually increases, while the content of Al2Y does not change much. As the Li content increases from 4% to 10%, the ultimate tensile strength and hardness of the as-cast LAZx32-0.5Y alloys gradually decrease while the elongation gradually increases. The corresponding fracture mechanism changes from cleavage fracture to quasi-cleavage fracture and then to microporous aggregation fracture. This is mainly attributed to the decrease of α-Mg and the increase of β-Li in the alloy. When the Li content continues to increase to 10% and 14%, the yield strength, ultimate tensile strength and hardness of the as-cast LAZx32-0.5Y alloys gradually increase, while the elongation decreases sharply, which is mainly attributed to the nano-scale MgLi2Al uniformly distributed in the β-Li matrix. 相似文献
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In this study, we report results of an investigation into the failure of Ni60Nb15Ti15Zr10 amorphous alloys occurring during hydrogen permeation performed at 473 K and 573 K. However, the amorphous membrane did not
fail during test performed at higher temperatures (673 K and 773 K). The failure of the Pd-coated Ni60Nb15Ti15Zr10 amorphous ribbon is attributed to the cracking of the hydrogenated Pd coating induced by the formation of α′ hydride phase
in the low temperature range.
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Metal Science and Heat Treatment - 相似文献
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《中国有色金属学会会刊》2021,31(11):3394-3404
The effects of trace Ag element on the precipitation behaviors and mechanical properties of the Mg−7.5Gd− 1.5Y−0.4Zr (wt.%) alloy by means of tensile test, X-ray diffractometry, scanning electron microscopy, electron backscattered diffractometry, and scanning transmission electron microscopy. There is an unusual texture (〈0001〉//extrusion direction) in the extruded Mg−Gd−Y−Zr alloys containing 0.5 wt.% Ag. During the aging periods at 225 °C, the addition of the trace Ag does not form new precipitates, just accelerates aging kinetics, and refines β′ precipitates, thereby increasing the number density of the β′ precipitates by Ag-clusters. Moreover, the Mg−Gd−Y−Zr alloy containing 0.5 wt.% Ag shows the most excellent synergy of strength and plasticity (408 MPa of ultimate tensile strength, 265 MPa of yield strength, and 12.9% of elongation to failure) after peak-aging. 相似文献
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The correlation between the oxide impedance and corrosion behavior of two series of Zr−Nb−Sn−Fe−Cu alloys was evaluated. Corrosion
tests were performed in a 70 ppm LiOH aqueous solution at 360°C for 300 days. The results of the corrosion tests revealed
that the corrosion behavior of the alloys depended on the Nb and Sn content. The impedance characteristics for the pre- and
post-transition oxide layers formed on the surface of the alloys were investigated in sulfuric acid at room temperature. From
the results, a pertinent equivalent circuit model was preferably established, explaining the properties of double oxide layers.
The impedance of the oxide layers correlated with the corrosion behavior; better corrosion resistance always showed higher
electric resistance for the inner layers. It is thus concluded that a pertinent equivalent circuit model would be useful for
evaluating the long-term corrosion behavior of Zr−Nb−Sn−Fe−Cu alloys. 相似文献
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Reversed austenite transformation and existence of retained austenite during tempering of the super martensitic stainless
steel of Fe-14Cr-7Ni-0.3Nb-0.7Mo-0.03C were studied by means of experiments on microstructure and X-ray diffraction, and tensile
and hardness tests. Acicular type retained austenite at the lath boundary of martensite with the interior appeared after solution
annealing. This retained austenite still existed, and reversed austenite was not formed, with tempering up to 24h at 450°C.
The reversed austenite began to form above 550°C, and the volume fraction of reversed austenite decreased with increasing
tempering temperature after showing a maximum value of 19.2% at 650°C. This maximum volume fraction of reversed austenite
was responsible for the lowest value of strength and hardness. The Ni contents of plate type reversed austenite and the surrounding
matrix increased and decreased respectively, implying that the reversed austenite was formed as a result of nickel diffusion.
The orientation relationships between reversed austenite and the surrounding matrix showed a K-S relationship of and. 相似文献
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《中国有色金属学会会刊》2020,30(7):1717-1730
The effect of thermal exposure at 350 °C for 200 h on microstructure and mechanical properties was investigated for Al−Si−Cu−Ni−Mg alloy, which was produced by permanent mold casting (PMC) and high pressure die casting (HPDC). The SEM and IPP software were used to characterize the morphology of Si phase in the studied alloys. The results show that the thermal exposure provokes spheroidization and coarsening of eutectic Si particles. The ultimate tensile strength of the HPDC alloy after thermal exposure is higher than that of the PMC alloy at room temperature. However, the TEPMC and TEHPDC alloys have similar tensile strength around 67 MPa at 350 °C. Due to the coarsening of eutectic Si, the TEPMC alloy exhibits better creep resistance than the TEHPDC alloy under studied creep conditions. Therefore, the alloys with small size of eutectic Si are not suitably used at 350 °C. 相似文献