Strengthening austenitic nonmagnetic steels by phase hardening

A ZK61-Y magnesium (Mg) alloy wheel hub was prepared via liquid forging—isothermal forging process. The effects of Y-element contents on the microstructure and mechanical properties of liquid forging blanks were investigated. The formation order of the second phase was I-phase (Mg3Zn6Y) → W-phase (Mg3Zn3Y2) → Z-phase (Mg12ZnY) with the increase of the Y-element content. Meanwhile, the I-phase and Z-phase formed in the liquid forging process were beneficial to the grain refinement. The numerical simulation of the isothermal forging process was carried out to analyze the effects of forming temperature on the temperature and stress field in the forming parts using the software Deform-3D. Isothermal forging experiments and post heat treatments were conducted. The influence of isothermal forging temperature, heat treatment temperature and preservation time on the microstructure and mechanical properties of the forming parts were also studied. The dynamic recrystallization (DRX), second-phase hardening, and work hardening account for the improvement of properties after the isothermal forging process. The forming part forged at 380 °C displayed the outstanding properties. The elongation, yield strength, and ultimate tensile strength were 18.5%, 150 MPa and 315 MPa, respectively. The samples displayed an increased elongation and decreased strength after heat treatments. The 520 °C—1 h sample possessed the best mechanical properties, the elongation was 25.5%, the yield stress was 125 MPa and the ultimate tensile strength was 282 MPa. This can be ascribed to the recrystallization and the elimination of working hardening. Meanwhile, the second phase transformation (I-phase → W-phase → Mg2Y + MgZn2), dissolution, and decomposition can be observed, as well.

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Effect of external and phase hardening on the hydrogen penetration rate in ferrite

Metal Science and Heat Treatment ◽

10.1007/bf00657613 ◽

1965 ◽

Vol 7 (4) ◽

pp. 221-223

Author(s):

V. A. Gol'tsov ◽

P. V. Gel'd ◽

M. M. Steinberg

Keyword(s):

Penetration Rate ◽

Phase Hardening ◽

Hydrogen Penetration

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Effects of phase hardening on martensite transformations in high-nickel steel

Scripta Metallurgica et Materialia ◽

10.1016/0956-716x(90)90569-3 ◽

1990 ◽

Vol 24 (1) ◽

pp. 75-78

Author(s):

V.I. Bondar' ◽

V.V. Girzhon ◽

V.E. Danil'chenko

Keyword(s):

Nickel Steel ◽

Phase Hardening ◽

High Nickel ◽

Martensite Transformations ◽

High Nickel Steel

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Enhancement of Tribological Performance of 6061 Aluminum Alloy by Second Phase Hardening via Friction Stir Processing

ASME/STLE 2011 Joint Tribology Conference ◽

10.1115/ijtc2011-61203 ◽

2011 ◽

Cited By ~ 1

Author(s):

C. Lorenzo-Martin ◽

O. Ajayi ◽

G. Fenske

Keyword(s):

Aluminum Alloy ◽

Friction Stir Processing ◽

Performance Enhancement ◽

Base Material ◽

Bearing Steel ◽

Tribological Performance ◽

Second Phase ◽

Phase Hardening ◽

Friction Stir ◽

B4c Particle

The properties of metallic alloys can be substantial modified by the addition of a second phase particles. This is especially noticeable when hard particles are incorporated in a relatively soft matrix, often resulting in improved mechanical and tribological performance. This paper presents the results of our study on mechanical and tribological performance enhancement of 6061 Aluminum alloys by incorporation of B4C particle via Friction stir processing (FSP). Unidirectional ball on flat friction and wear tests were conducted with a base material, friction stir processed 6061-Al and 6061-Al doped with B4C particles via FSP against 52100 bearing steel balls under dry sliding conditions. The incorporation of particles not only reduced friction by 30% but also reduced wear by 2 orders of magnitude compared to unprocessed base and FSP material without particles incorporation. FSP alone without particles addition did not have a significant effect on the tribological behavior of the tested aluminum alloy.

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The dry wear of steels II. Interpretation and special features

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1965.0002 ◽

1965 ◽

Vol 257 (1077) ◽

pp. 51-70 ◽

Cited By ~ 67

Keyword(s):

Oxide Film ◽

Phase Change ◽

Strain Hardening ◽

Frictional Heating ◽

Combined Effects ◽

Phase Hardening ◽

Special Effects ◽

Severe Wear ◽

Wear Rates ◽

Mild Wear

The pattern of wear outlined in part I is interpreted in the light of further experiments which reveal that the change from severe wear to mild is governed by the hardness and state of oxidation of the surfaces. At light loads (< T 1) severe wear is inhibited by the combined effects of strain hardening and oxidation. At higher loads (> T 2) mild wear recurs primarily as a consequence of a change of phase induced by frictional heating. The hardness accompanying the phase change is great enough, initially, to suppress severe wear without the intervention of an oxide film. At loads immediately above T 2, however, the hardness tends to fall if rubbing is prolonged and oxidation is again essential to preserve the mild wear state. Sustained phase-hardening does not occur until a higher load, roughly coinciding with the T 3 transition, is attained and this finding has an important bearing on the influence of inert atmospheres. The onset of permanent hardening is not responsible for the divergent pin and ring wear rates at T 3, though the phenomena may be linked by the magnitude of the temperatures required to cause phase-hardening; the T 3 transition and the trend at higher loads have been identified as special effects associated with the thermal asymmetry of the rubbing system.

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Influence of phase hardening on transition broadening in a (1−x)NaNbO3−xLiNbO3 system

Technical Physics Letters ◽

10.1134/1.1262640 ◽

1999 ◽

Vol 25 (10) ◽

pp. 800-801

Author(s):

I. V. Pozdnyakova ◽

L. A. Reznichenko ◽

V. G. Gavrilyachenko

Keyword(s):

Phase Hardening

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Mechanical behavior and fractographic analysis of a TiNi alloy with various thermomechanical treatment

MATEC Web of Conferences ◽

10.1051/matecconf/201929800019 ◽

2019 ◽

Vol 298 ◽

pp. 00019 ◽

Cited By ~ 1

Author(s):

Anna Churakova ◽

Anna Yudahina ◽

Elina Kayumova ◽

Nikita Tolstov

Keyword(s):

Dislocation Density ◽

Thermal Cycling ◽

Thermomechanical Treatment ◽

Martensitic Transformations ◽

Coarse Grained ◽

Tini Alloy ◽

Phase Hardening ◽

Cold Upsetting ◽

Cycling Treatment ◽

Ultrafine Grained

Influence of thermomechanical treatment (deformation, thermal cycling treatment in the temperature range of martensitic transformations B2-B19’) on the TiNi alloys’ mechanical behaviour and fracture was studied. Different states were considered, they are initial coarse-grained (CG), ultrafine-grained (UFG) after ECAP (with a grain size of 200 nm), the state after ECAP and cold upsetting by 30% - UFG state with high dislocation density. It was shown that thermal cycling causes some increase in dislocation density, strength and microhardness in all the states. Thermal cycling of UFG alloys allows forming the states with non-equilibrium grain boundaries, with additional dislocations of “phase hardening”. The nature of the fracture was analysed in the TiNi alloy in various states.

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