Effect of phase composition and deformation conditions on the hydrogen plasticization of hydrogen-containing titanium alloys

The effect of hydrogen as an alloying element on the plastic-deformation characteristics of commercial titanium and Ti-6Al and Ti-6Al-4V alloys is studied. A relation between the strain resistance of the alloys and their phase composition is established over a wide temperature range. The parameters of the hydrogen hardening of the alloys in the single-phase β field and hydrogen plasticization conditions are determined.     

Effect of composition and deformation temperature on the annealing behavior of stacking faults in α-Cu-Ge alloys

The disappearance of stacking faults in filings of α-Cu-Ge alloys (5.6, 6.7, 7.7, and 8.5 at. pct Ge) prepared at various deformation temperatures has been studied with X-ray diffraction. The faults anneal out in two stages, the second of which is diffusion controlled. The time necessary to anneal out all of the faults depends on both alloy composition and deformation temperature. The dependence of the number of faults on the deformation temperature has also been determined.     

Effect of scandium on the phase composition and mechanical properties of ABM alloys

The effect of scandium on the composition and mechanical properties of ABM-1 alloys (Al-30% Be-5% Mg) is studied. The scandium content is varied from 0.1 to 0.5 wt %. It is established that, in the studied part of the Al-Be-Mg-Sc system, an aluminum solid solution (Al) and the ScBe₁₃ compound are in equilibrium with a beryllium solid solution (Be). Magnesium dissolves in both the aluminum component and the ScBe₁₃ compound. The strengthening effect related to the decomposition of the solid solution and the precipitation of Al₃Sc cannot be extended to the strengthening of ABM-type alloys. Additions of 0.1–0.15 wt % Sc only weakly improve the mechanical properties of the alloys due to the refinement of beryllium-component grains. At high scandium contents, the strength increases insignificantly due to primary precipitation of ScBe₁₃ and the plasticity decreases simultaneously.     

Effect of composition on the solidification behavior of several Ni-Cr-Mo and Fe-Ni-Cr-Mo alloys

The microstructural development of several Ni-Cr-Mo and Fe-Ni-Cr-Mo alloys over a range of conditions has been examined. A commercial alloy, AL-6XN, was chosen for analysis along with three experimental compositions to isolate the contribution of individual alloying elements to the overall microstructural development. Detailed microstructural characterization on each alloy demonstrated that the observed solidification reaction sequences were primarily dependent on the segregation behavior of molybdenum (Mo), which was unaffected by the large difference in cooling rate between differential thermal analysis (DTA) samples and welded specimens. This explains the invariance of the amount of eutectic constituent observed in the microstructure in the welded and DTA conditions. Multicomponent liquidus projections developed using the CALPHAD approach were combined with solidification path calculations as a first step to understanding the observed solidification reaction sequences. Discrepancies between the calculations and observed reaction sequences were resolved by proposing slight modifications to the calculated multicomponent liquidus projections.     

Effect of cerium content on the deformation behavior of rapidly solidified Al-Fe-Ce alloys

The deformation behavior of a rapidly solidified Al-8.9Fe-6.9Ce (wt pct) alloy was studied in the temperature range of 250 °C to 350 °C and stress range of 20 to 175 MPa. The stress exponents and activation energies suggest that the alloy exhibits a pronounced diffusional creep regime with a transition to power law creep behavior at stresses beyond 60 MPa. Comparing these data with those obtained earlier for an Al-8.8Fe-3.7Ce alloy, it was found that in the diffusional creep regime, the Ce content had no effect on the creep rate. However, in the power law creep regime, a strong dependence on the precipitate spacing, as predicted by the structureinvariant creep law,^[5] was observed. The higher volume fraction of precipitates in the Al-8.9Fe6.9Ce alloy causes a decrease in the power law creep rates by a factor of 5. Formerly Graduate Student. Formerly Assistant Professor, University of Illinois at Urbana-Champaign.     

Effect of test temperature on the dynamic torsional deformation behavior of two aluminum-lithium alloys

The objective of the present study is to investigate the effect of test temperature on the dynamic torsional deformation behavior of two Al-Li alloys, i.e., 2090 and 8090 alloys. Dynamic torsional tests were conducted using a torsional Kolsky bar at room temperature and a low temperature (−196 °C), and the torsionally deformed regions and the fracture surfaces of the tested specimens were examined. The dynamic properties of the two Al-Li alloys at the low temperature were improved, owing to the modification of the deformation behavior. The dynamic deformation behavior at room temperature was dominated by intergranular cracks due to planar slips and by crack propagation along the grain boundaries. At the low temperature, plastic deformation proceeded more homogeneously as planar slip was prevented. These results indicated that the overall deformation mode of both the Al-Li alloys changed from planar slip to homogeneous deformation with decreasing temperature, resulting in the improvement of cryogenic properties under dynamic torsional loading.     

Structure and phase composition of Ti-Ni-Cu alloys

Conclusions Alloying with 4–10% Cu has an inoculating action on the structure of the eutectic titanium-nickel alloy, resulting in its refinement and a redistribution of its constituents, improves the wetting of diamond by the alloy, and lowers the latter's melting point. This opens up the possibility of using such materials in the formulation of diamond-containing composites. The addition of 20–30% Cu results in the formation of three-phase alloys of intermetallic character, which are characterized by a low melting point (930°C), a finegrained structure, and satisfactory adhesion to diamond, but also by low strength and ductility.Translated from Poroshkovaya Metallurgiya, No. 7 (259), pp. 52–57, July, 1984.     

H65黄铜ECAP变形规律和第二相取向演变的数值模拟

采用Deform-2D有限元软件模拟H65黄铜ECAP变形实验, 分析H65黄铜ECAP变形规律及第二相取向的演变, 并结合H65黄铜ECAP变形实验验证H65黄铜ECAP变形过程中第二相取向的演变.结果表明:ECAP变形过程可分为开始变形载荷逐渐增加,逐渐变形载荷增加迅速,变形稳定载荷一定范围内波动,退出变形载荷减小迅速4个阶段;试样中心的等效应变分布随挤压道次的增加而逐渐趋于稳定,并集中在试样的3~9 mm区域内;偶数道次挤压,可以获得等效应变较均匀的变形件;模具内角转角处是裂纹优先产生的地方.第二相取向的演变模拟与实验基本一致,即试样中心水平第二相,经奇数道次挤压后,大约与水平正方向呈约30 °规则的分布在基体中;经偶数道次挤压后,心部和边部的取向各不相同.试样中心竖直第二相,各道次挤压后,取向基本保持不变.      

Effect of tungsten particle shape on dynamic deformation and fracture behavior of tungsten heavy alloys

The effect of the tungsten particle shape on the dynamic deformation and fracture behavior of tungsten heavy alloys was investigated. Dynamic torsional tests were conducted using a torsional Kolsky bar for five alloys, one of which was fabricated by the double-cycled sintering process, and then the test data were compared via microstructures, mechanical properties, adiabatic shear banding, and fracture mode. The dynamic torsional test results indicated that in the double-sintered tungsten alloy whose tungsten particles were very coarse and irregularly shaped, cleavage fracture occurred in the central area of the gage section with little shear deformation, whereas shear deformation was concentrated in the central area of the gage section in the other alloys. The deformation and fracture behavior of the double-sintered alloy correlated well with the observation of the impacted penetrator specimen and the in situ fracture test results, i.e., microcrack initiation at coarse tungsten particles and cleavage crack propagation through tungsten particles. These findings suggested that the cleavage fracture mode would be beneficial for the self-sharpening effect, and, thus, the improvement of the penetration performance of the double-sintered tungsten heavy alloy would be expected.     

Effect of tungsten particle shape on dynamic deformation and fracture behavior of tungsten heavy alloys

The effect of the tungsten particle shape on the dynamic deformation and fracture behavior of tungsten heavy alloys was investigated. Dynamic torsional tests were conducted using a torsional Kolsky bar for five alloys, one of which was fabricated by the double-cycled sintering process, and then the test data were compared via microstructures, mechanical properties, adiabatic shear banding, and fracture mode. The dynamic torsional test results indicated that in the double-sintered tungsten alloy whose tungsten particles were very coarse and irregularly shaped, cleavage fracture occurred in the central area of the gage section with little shear deformation, whereas shear deformation was concentrated in the central area of the gage section in the other alloys. The deformation and fracture behavior of the double-sintered alloy correlated well with the observation of the impacted penetrator specimen and the in situ fracture test results, i.e., microcrack initiation at coarse tungsten particles and cleavage crack propagation through tungsten particles. These findings suggested that the cleavage fracture mode would be beneficial for the self-sharpening effect, and, thus, the improvement of the penetration performance of the double-sintered tungsten heavy alloy would be expected.     

Effect of retained austenite on the yielding and deformation behavior of a dual phase steel

Tensile tests were conducted on a vanadium containing dual phase steel at temperatures between −53 and + 187°C to determine the effect of retained austenite stability on tensile properties. The transformation of retained austenite to martensite with stress/strain was shown to be a contributing factor in the yielding and strain hardening behavior of the dual phase steel. Increasing the stability of the austenite, by increasing the test temperature, caused the expected shift in the austenite to martensite strain transformation to higher strains. This led to a lower initial strain hardening exponent which increased with strain, compared to the ambient and sub-zero temperature deformation where the initial strain hardening exponent was higher but decreased with strain. The former behavior, which accentuated the strain hardening ability at higher strains, led to an increase in the uniform and total elongations, suggesting that the ductility of dual phase steels can be further improved by optimizing the stability of the retained austenite.     

Evolution of the structure and phase composition of rapidly solidified Al-Mg-Mn-Sc-Zr alloys during deformation in a bridgman anvil

Metallography and electron microscopy are used to study the formation of submicrocrystalline and nano-structured states in Al-Mg-Mn alloys with scandium and zirconium during shear at a high hydrostatic pressure. The evolution of the structure and changes in the hardness of the alloys are discussed in relation to their composition and casting and heat treatment conditions.     

奥氏体形变对50CrV4钢相变行为的影响

利用Thermecmastor-Z型热模拟试验机,结合金相显微镜(OM)、扫描电镜(SEM)、维氏硬度计等,系统研究了奥氏体区变形对50CrV4钢连续冷却相变和等温相变规律的影响。建立了试验钢动态CCT曲线。研究结果表明,奥氏体变形能促进连续冷却转变过程中铁素体-珠光体、贝氏体转变,但亦可提高奥氏体的机械稳定性,进而抑制马氏体转变,Ms点由331.6℃(奥氏体未变形)降低至291℃(950℃下变形50%+890℃下变形50%,变形速率均为5s-1,变形后冷速为20℃/s)。当轧后冷速小于0.5℃/s时,试验钢中可获得铁素体+珠光体组织。此外,在研究不同变形量对试验钢等温相变规律影响时发现,650℃等温时,试验钢中发生铁素体-珠光体相变。随着变形量的增加(由30%增加至50%),其等温相变动力学加快(相变完成时间由197.6s减小至136.5s),铁素体体晶粒尺寸、珠光体片层间距减小,硬度增加。     

Effect of severe plastic deformation on the phase and structural transformations and mechanical properties of metastable austenitic Ti-Ni alloys

The effect of deformation under pressure and severe plastic torsional deformation (SPTD) on the structure and mechanic properties of Ti-Ni alloys is studied. It is found that, as an external load is applied, metastable austenitic alloys of the Ti-Ni system undergo the B2 → B19′ transformation. The SPTD Ti-Ni alloys are characterized by high mechanical properties and high thermal stability of their nanostructured state and properties.     

预退火对Al-Pb和Al-Pb-Cu纳米相复合结构合金Pb相长大行为的影响

利用X射线衍射仪和扫描电镜,研究预退火对机械合金化制备的Al-10%Pb和Al-10%Pb-4.5%Cu(质量分数)纳米相复合结构合金中Pb相长大行为的影响,此机械合金化制备的Al-10%Pb和Al-10%Pb-4.5%Cu合金应在873 K保温10 min后进行预退火。结果表明,预退火后的Al-10%Pb合金在823K退火时,Pb相发生了异常长大,且预退火可促进Pb相的异常长大,这与预退火促进基体Al的异常长大有关。预退火后的Al-10%Pb-4.5%Cu合金中Pb相的长大行为仍可用LSW理论描述,但其长大速率明显大于未预退火的Al-10%Pb-4.5%Cu合金中Pb相的长大速率。这是由预退火使Pb相的长大驱动力增加所引起的。     

Room-temperature deformation behavior of directionally solidified multiphase Ni-Fe-Al alloys

Directionally solidified (DS) β + (γ + γ′) Ni-Fe-Al alloys have been used to investigate the effect of a ductile second phase on the room-temperature mechanical behavior of a brittle 〈001〉-oriented β (B2) phase. The ductile phase in the composite consisted of a fine distribution of ordered γ′ precipitates in a γ (fcc) matrix. Three microstructures were studied: 100 pct lamellar/rod, lamellar + proeutectic β, and discontinuous γ. The β matrix in the latter two microstructures contained fine-scale bcc precipitates formed due to spinodal decomposition. Room-temperature tensile ductilities as high as 12 pct and fracture toughness (K _Q ) of 30.4 MPa √m were observed in the 100 pct lamellar/rod microstructure. Observations of slip traces and dislocation substructures indicated that a substantial portion of the ductility was a result of slip transfer from the ductile phase to the brittle matrix. This slip transfer was facilitated by the Kurdjumov-Sachs (KS) orientation relationship between the two phases and the strong interphase interface which showed no decohesion during deformation. In microstructures which show higher values of tensile ductility and fracture toughness, 〈100〉 slip was seen in the β phase, whereas 〈111〉 slip was seen in the β phase in the microstructure which showed limited ductility. The high ductility and toughness are explained in terms of increased mobile dislocation density afforded by interface constraint. The effect of extrinsic toughening mechanisms on enhancing the ductility or toughness is secondary to that of slip transfer.