Long-Range Ordering: An Approach to Synthesize Nanoscale Ni-Mo-Based Superlattices with High Strength and High Ductility

It is shown that long-range ordering in certain alloys based upon the Ni-Mo system can provide a viable means for synthesizing bulk nanoscale materials combing high strength and high ductility. Three alloys were included in the study with nominal chemical compositions of Ni-27Mo, Ni-27Mo-0.03B, and Ni-27Mo-12Cr all in weight %. Ordering was induced by thermal aging at 700 oC resulting in a D1a superlattice (Ni4Mo) in the Ni-27Mo and Ni-27Mo-0.03B alloys, and a Pt2Mo-type superlattice [Ni2(Cr,Mo)] in the Ni-27Mo-12Cr alloy. During the early stages of aging, atomic order in the Ni-27Mo alloy was completed homogeneously in the matrix resulting in a nanoscale superlattice with high strength and high ductility, however, a considerable loss of ductility occurred after extended aging. The results suggested that this behavior was not related to the degree of atomic order but rather to a change in morphology resulting from a heterogeneous ordering reaction at grain boundaries promoted by strain-induced recrystallization. Although a nanoscale superlattice combining high strength and high ductility could be synthesized in the Ni-27Mo alloy by proper aging treatment, it is demonstrated that the heterogeneous ordering reaction could be suppressed by the addition of boron or chromium to improve the thermal stability of the alloy system. On the average, a combination of about 800 MPa yield strength and 40% tensile elongation at room temperature could be achieved in the alloys studied. Deformation in the ordered state is found to occur by twinning, which has been related to the crystallography of the disorder-order transformation.

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Application of long-range ordering in the synthesis of a nanoscale Ni2 (Cr,Mo) superlattice with high strength and high ductility

Materials Science and Engineering A ◽

10.1016/j.msea.2008.09.027 ◽

2009 ◽

Vol 500 (1-2) ◽

pp. 188-195 ◽

Cited By ~ 29

Author(s):

H.M. Tawancy ◽

M.O. Aboelfotoh

Keyword(s):

Long Range ◽

High Strength ◽

High Ductility ◽

Long Range Ordering

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Synthesis of Bulk Nanostructured DO22Superlattice of Ni3(Mo, Nb) with High Strength, High Ductility, and High Thermal Stability

Journal of Nanomaterials ◽

10.1155/2012/387694 ◽

2012 ◽

Vol 2012 ◽

pp. 1-7 ◽

Cited By ~ 7

Author(s):

H. M. Tawancy

Keyword(s):

Thermal Stability ◽

Parent Phase ◽

Aging Treatment ◽

High Strength ◽

Nanostructured Material ◽

High Thermal Stability ◽

Cubic Phase ◽

Face Centered Cubic ◽

High Ductility ◽

Bulk Nanostructured Material

We show that a bulk nanostructured material combining high strength, high ductility, and high thermal stability can be synthesized in a Ni-Mo-Nb alloy with composition approaching Ni3(Mo, Nb). By means of a simple aging treatment at700°C, the grains of the parent face-centered cubic phase are made to transform into nanosized ordered crystals with DO22superlattice maintaining a size of 10–20 nm after up to 100 hours of aging and corresponding room-temperature yield strength of 820 MPa and tensile ductility of 35%. Deformation of the superlattice is found to predominantly occur by twinning on{111}planes of the parent phase. It is concluded that, although the respective slip systems are suppressed, most of the twinning systems are preserved in the DO22superlattice enhancing the ductility.

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Interpretation of Specific Strength-Over-Resistivity Ratio in Cu Alloys

Materials ◽

10.3390/ma14237150 ◽

2021 ◽

Vol 14 (23) ◽

pp. 7150

Author(s):

Hongming Li ◽

Shuang Zhang ◽

Yajun Zhao ◽

Xiaona Li ◽

Fushi Jiang ◽

...

Keyword(s):

Electrical Resistivity ◽

Lower Limit ◽

High Strength ◽

Alloy System ◽

Resistivity Ratio ◽

Specific Strength ◽

Cu Alloys ◽

The Matrix ◽

In Series ◽

Pure Cu

Reaching simultaneously high mechanical strength and low electrical resistivity is difficult as both properties are based on similar microstructural mechanisms. In our previous work, a new parameter, the tensile strength-over-electrical resistivity ratio, is proposed to evaluate the matching of the two properties in Cu alloys. A specific ratio of 310 × 108 MPa·Ω−1·m−1, independent of the alloy system and thermal history, is obtained from Cu-Ni-Mo alloys, which actually points to the lower limit of prevailing Cu alloys possessing high strength and low resistivity. The present paper explores the origin of this specific ratio by introducing the dual-phase mechanical model of composite materials, assuming that the precipitate particles are mechanically mixed in the Cu solid solution matrix. The strength and resistivity of an alloy are respectively in series and parallel connections to those of the matrix and the precipitate. After ideally matching the contributions from the matrix and the precipitate, the alloy should at least reach half of the resistivity of pure Cu, i.e., 50%IACS, which is the lower limit for industrially accepted highly conductive Cu alloys. Under this condition, the specific 310 ratio is related to the precipitate-over-matrix ratios for strength and resistivity, which are both two times those of pure Cu.

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Fabricate of High-Strength and High-Conductivity Cu–Cr–Si Alloys through ECAP-Bc and Aging Heat Treatment

Materials ◽

10.3390/ma13071603 ◽

2020 ◽

Vol 13 (7) ◽

pp. 1603 ◽

Cited By ~ 1

Author(s):

Tingbiao Guo ◽

Junjie Wang ◽

Yibo Wu ◽

Xiaoyang Tai ◽

Zhi Jia ◽

...

Keyword(s):

Electrical Conductivity ◽

Electron Backscatter Diffraction ◽

Aging Treatment ◽

High Strength ◽

High Conductivity ◽

Grain Structure ◽

X Ray Diffraction ◽

Angular Pressing ◽

The Matrix ◽

Backscatter Diffraction

The effect of equal channel angular pressing (ECAP) through the route Bc and aging treatment on the grain structure and properties of the Cu–1Cr–0.2Si alloy was investigated. Microstructure was detected by scanning electron microscopy (SEM), x-ray diffraction (XRD), and electron backscatter diffraction (EBSD) and the mechanical properties and electrical conductivity were tested. Results shown that after ECAP, accompanying the grains refined to nano-and submicron-structure, the Cr particles were gradually spread along the grain boundaries (GBs), aging treatment promoted Cr particles dispersed in the matrix. ECAP greatly increased the ultimate tensile strength (UTS) while having a small effect on the conductivity, and aging treatment increased electrical conductivity. The stable {111}<110> texture after ECAP and the lower dislocation density after aging treatment maybe the main reasons for the high conductivity of the material.

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Anti-Twinning in an Ni-Mo-Cr Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.203-204.254 ◽

2013 ◽

Vol 203-204 ◽

pp. 254-257

Author(s):

Mirosław Wróbel ◽

Elżbieta Stępniowska ◽

Stanisław Dymek

Keyword(s):

Long Range ◽

The Body ◽

Type I ◽

Face Centered Cubic ◽

The Matrix ◽

The Face ◽

Face Centered ◽

Long Range Ordering ◽

Mechanical Twins ◽

Crystallographic Orientations

Two morphological types of mechanical twins occur in the microstructure of cold rolled Ni-Mo-Cr alloy: long – passing over whole grains and micro-twins – confined to individual long range ordered domains. Long mechanical twins were only formed in the disordered alloy. Such twins are typical for metals with the face centered cubic structure with relatively low stacking fault energy. They do not form in the grains with twinning prohibited crystallographic orientations, e.g. {110}. Both types of twins were found in an alloy subjected to prolong annealing at 650 °C. The annealing induces long range ordering reaction leading to the formation of ordered domains with the body centered orthorombic crystal structure (oI8). The twins were of type I, type II, compound twins or pseudo-twins, depending on the crystallographic orientation of the ordered phase in relation to the matrix. It was found that twins of such types were formed even in grains with the {110} orientation and result from the anti-twinning deformation. However, in this orientation they were confined to ordered domains rather than developed into the long form crossing entire grains. On the other hand, the long twins of various types were formed in grains with other twinning favoring crystallographic orientations.

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Effect of One-Step and Two-Step Aging Treatments on Microstructure and Properties of an Al-9.0Zn-2.0Mg-2.0Cu Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.949 ◽

2018 ◽

Vol 941 ◽

pp. 949-954 ◽

Cited By ~ 1

Author(s):

Kai Wen ◽

Bai Qing Xiong ◽

Yong An Zhang ◽

Zhi Hui Li ◽

Xi Wu Li ◽

...

Keyword(s):

Electron Microscopy ◽

Aging Treatment ◽

High Strength ◽

High Resolution Electron Microscopy ◽

Slow Increase ◽

Microstructure Observation ◽

Resolution Electron ◽

The Matrix ◽

One Step ◽

Diffraction Patterns

Aging treatments of an Al-9.0Zn-2.0Mg-2.0Cu alloy, which belongs to high strength aluminum alloy widely used in aerospace industry, are investigated by various techniques, including hardness, electrical conductivity, mechanical properties, transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The result shows that hardness and conductivity for one-step aging treatment increase with aging time prolongs while those for two-step aging treatment exhibit increment and decrement, respectively. Besides, the ultimate tensile strength (UTS) and yield strength (YS) for one-step and two-step aging treatments show slow increase and obvious decrease, respectively. Based on these, typical T6 and T76 aging regimes are extracted for microstructure observation. The matrix precipitates for the T6 alloy have small size and dispersive distribution while that for the T76 alloy has big size and sparse distribution. The grain boundary precipitates for both exhibit discontinuous distribution and the T76 alloy has larger size and broader precipitate free zones. The selected area diffraction patterns and HREM observations reveal that main precipitates for the T6 alloy are GPI zone, GPII zone and η' phase while for the T76 alloy are η' phase and η phase.

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Spontaneous Lateral Composition Modulation in III-V Semiconductor Alloys

MRS Bulletin ◽

10.1557/s088376940003339x ◽

1997 ◽

Vol 22 (7) ◽

pp. 38-43 ◽

Cited By ~ 38

Author(s):

J. Mirecki Millunchick ◽

R.D. Twesten ◽

S.R. Lee ◽

D.M. Follstaedt ◽

E.D. Jones ◽

...

Keyword(s):

Long Range ◽

High Speed ◽

Short Range ◽

Carrier Mobility ◽

Alloy System ◽

Semiconductor Alloys ◽

Chemical Ordering ◽

Short Range Ordering ◽

Device Structures ◽

Long Range Ordering

The application of III-V semiconductor alloys in device structures is of importance for high-speed microelectronics and optoelectronics. These alloys have allowed the device engineer to tailor material parameters such as the bandgap and carrier mobility to the need of the device by altering the alloy composition. When using ternary or quaternary materials, the device designer presumes that the alloy is completely disordered, without any correlation between the atoms on the cation (anion) sublattice. However the thermodynamics of the alloy system often produce material that has some degree of macroscopic or microscopic ordering. Short-range ordering occurs when atoms adopt correlated neighboring positions over distances of the order of a few lattice spacings. This can be manifested as the preferential association of like atoms, as in clustering, or of unlike atoms, as in chemical ordering (e.g., CuPt ordering). Long-range ordering occurs over many tens of lattice spacings, as in the case of phase separation. In either short-range or long-range ordering, the band structure and the crystal symmetry are greatly altered. Therefore it is absolutely critical that the mechanisms be fully understood to prevent ordering when necessary or to exploit it when possible.

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Lattice imaging of precipitates in Al-Zn-Mg alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143651 ◽

1986 ◽

Vol 44 ◽

pp. 412-413

Author(s):

C. K. Wu

Keyword(s):

Grain Boundaries ◽

Homogeneous Nucleation ◽

Alloy System ◽

Mg Alloy ◽

List Type ◽

Lattice Structures ◽

Type Number ◽

Orientation Relationships ◽

Lattice Imaging ◽

The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

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Microstructure of resistance spot welding of maraging steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177635 ◽

1990 ◽

Vol 48 (4) ◽

pp. 900-901

Author(s):

I. Neuman ◽

S.F. Dirnfeld ◽

I. Minkoff

Keyword(s):

Maraging Steel ◽

Spot Welding ◽

Lath Martensite ◽

Base Material ◽

Aging Treatment ◽

High Strength ◽

Maraging Steels ◽

Heat Treated ◽

Current Cycle ◽

Welding Processes

Experimental work on the spot welding of Maraging Steels revealed a surprisingly low level of strength - both in the as welded and in aged conditions. This appeared unusual since in the welding of these materials by other welding processes (TIG,MIG) the strength level is almost that of the base material. The maraging steel C250 investigated had the composition: 18wt%Ni, 8wt%Co, 5wt%Mo and additions of Al and Ti. It has a nominal tensile strength of 250 KSI. The heat treated structure of maraging steel is lath martensite the final high strength is reached by aging treatment at 485°C for 3-4 hours. During the aging process precipitation takes place of Ni3Mo and Ni3Ti and an ordered solid solution containing Co is formed.Three types of spot welding cycles were investigated: multi-pulse current cycle, bi-pulse cycle and single pulsle cycle. TIG welded samples were also tested for comparison.The microstructure investigations were carried out by SEM and EDS as well as by fractography. For multicycle spot welded maraging C250 (without aging), the dendrites start from the fusion line towards the nugget centre with an epitaxial growth region of various widths, as seen in Figure 1.

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