scholarly journals Improving the Tensile Properties of Additively Manufactured β-Containing TiAl Alloys via Microstructure Control Focusing on Cellular Precipitation Reaction

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 809
Author(s):  
Ken Cho ◽  
Hirotaka Odo ◽  
Keisuke Okamoto ◽  
Hiroyuki Y. Yasuda ◽  
Hirotoyo Nakashima ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundaries ◽  
Tensile Properties ◽  
Volume Fraction ◽  
Lamellar Spacing ◽  
Phase Region ◽  
Precipitation Reaction ◽  
Two Phase ◽  
Cellular Precipitation ◽  
High Temperature Tensile

The effect of a two-step heat treatment on the microstructure and high-temperature tensile properties of β-containing Ti-44Al-4Cr (at%) alloys fabricated by electron beam powder bed fusion were examined by focusing on the morphology of α2/γ lamellar grains and β/γ cells precipitated at the lamellar grain boundaries by a cellular precipitation reaction. The alloys subjected to the first heat treatment step at 1573 K in the α + β two-phase region exhibit a non-equilibrium microstructure consisting of the α2/γ lamellar grains with a fine lamellar spacing and a β/γ duplex structure located at the grain boundaries. In the second step of heat treatment, i.e., aging at 1273 K in the β + γ two-phase region, the β/γ cells are discontinuously precipitated from the lamellar grain boundaries due to excess Cr supersaturation in the lamellae. The volume fraction of the cells and lamellar spacing increase with increasing aging time and affect the tensile properties of the alloys. The aged alloys exhibit higher strength and comparable elongation at 1023 K when compared to the as-built alloys. The strength of these alloys is strongly dependent on the volume fraction and lamellar spacing of the α2/γ lamellae. In addition, the morphology of the β/γ cells is also an important factor controlling the fracture mode and ductility of these alloys.

Role of Equiaxed Primary Alpha (α׳) and Mechanical Properties of Ti-6Al-4V Alloy

2012 ◽  
Vol 510-511 ◽  
pp. 420-428
Author(s):  
A. Ahmad ◽  
A. Ali ◽  
G.H. Awan ◽  
K.M. Ghauri ◽  
R. Aslam
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Volume Fraction ◽  
Lamellar Microstructure ◽  
Phase Region ◽  
Bimodal Microstructure ◽  
Two Phase ◽  
Primary Alpha ◽  
Fully Lamellar

The paper presents the role of equiaxed α׳ in the bimodal microstructure to attain an optimal combination of ductility and strength. The study revealed that the production of bimodal microstructure and volume fraction of equiaxed α׳ were reliant on the forging temperature and subsequent heat treatment. The Ti-6Al-4V alloy was forged in the two phase region and different heat treatment cycles were employed to get the desired bimodal microstructure and thus the combination of strength and ductility. The mechanical properties of fully lamellar microstructure were compared with bimodal microstructure containing equiaxed α׳. The experimental results showed that the amount of equiaxed α׳ in the bimodal microstructure was critical for achieving a well-balanced profile of mechanical properties.

scholarly journals Effect of Reverse-phase Transformation Annealing Process on Microstructure and Mechanical Properties of Medium Manganese Steel

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1633 ◽  
Author(s):  
Yan Zhao ◽  
Lifeng Fan ◽  
Bin Lu
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
Volume Fraction ◽  
Lath Martensite ◽  
Phase Region ◽  
Manganese Steel ◽  
Reverse Phase ◽  
Two Phase ◽  
Fine Grain ◽  
Martensite Microstructure

In order to develop a third-generation automobile steel with powerful strength and elongation, we propose a method through high temperature quenching and two-phase region reverse-phase transformation annealing to develop such steel with 0.13% C and 5.4% Mn. To investigate the microstructure evolution and mechanical properties of manganese steel, SEM, XRD and TEM are employed in our experiments. Experimental results indicate that the microstructure after quenching is mainly lath martensite microstructure with average of lath width at 0.5 μm. The components of the steel after along with reverse-phase transformation annealing are ultra-fine grain ferrite, lath martensite and different forms of austenite microstructure. When the temperature at 625 °C, the components of the steel mainly includes lath martensite microstructure and ultra-fine grain ferrite and the fraction of austenite volume is only 5.09%. When the annealing temperature of reverse-phase transformation increase into 650 °C and 675 °C, the austenite appears in the boundary of the ferritic grain boundary and the boundary of lath martensite as the forms of bulk and lath. The phenomenon appears in the bulk of austenite, and the size of is 0.22 μm, 0.3 μm. The fraction of austenite volume is 22.34% at 675 °C and decreases into 9.32% at 700 °C. The components of austenite mainly includes ultra-fine grained ferrite and lath martensite. Furthermore, the density of decreases significantly, and the width of martensite increases into 0.32 μm. In such experimental settings, quenching at 930 °C with 20 min and at 675 °C with 30 min reverse-phase transformation annealing, the austenite volume fraction raises up to 22.34%.

Heat Treatment Recycling of Dual Phase Region and its Effect on Hardness, Microstructure and Corrosion Rate of Medium Carbon Steel

2014 ◽  
Vol 909 ◽  
pp. 100-104
Author(s):  
Mohamed A. Gebril ◽  
M.S. Aldlemey ◽  
Farag I. Haider
Keyword(s):  
Heat Treatment ◽  
Carbon Steel ◽  
Corrosion Rate ◽  
Phase Region ◽  
Medium Carbon Steel ◽  
Dual Phase ◽  
Two Phase ◽  
Medium Carbon ◽  
The Third ◽  
Hardness Increase

In this work, the investigations were carried out to study the effect of heat treatment at dual phase of austenite and ferrite on mechanical properties , microstructure and corrosion rate of low alloyed medium carbon steel. The specimens were divided into five groups, first group, specimens were heated to the duel phase region at temperature of 740°C soaked for 30 minutes and quenched in water. The second group, The specimens were heated to 740°C soaked for 30 minutes and quenched in water, then tempered to 480°C soaked for 20 minutes. The third group the specimens were heated to austenizing temperature of 840°C soaked for 30 minutes and quenched in water, then the specimens reheated to the dual phase region at 740°C, soaked for 30 minutes and quenched in water, then the specimens were tempered at temperature 480°C for 30 minutes. The forth group, the specimens were heated to austenizing temperature of 840°C soaked for 30 minutes and quenched in water, this process were repeated again before the specimens were thereafter heated to the dual phase region at temperature of 740°C, soaked for 20 minutes and quenched in water, then the specimens were tempered at temperature 480°C for 20 minutes. The fifth group, the specimens were heated to austenizing temperature of 840°C soaked for 20 minutes and quenched in water, this process were repeated two times again before the specimens were thereafter heated to the dual phase region at temperature of 740°C, soaked for 20 minutes and quenched in water, then the specimens finally tempered at temperature 480°C for 20 minutes. The results proved the hardness increase after heat treatment at first and second group, at third group the highest hardness value was due to formation of martensite and ferrite, but at fourth and fifth groups hardness decreases due to appearance of carbides particles, also corrosion rate usually increases with two phase at microstructure than stable one phase, third group have less corrosion rate than fourth and fifth due to carbides particles formation which lead to more corrosion rate due to three phases presents.

Tensile Property Improvements of Spinodal Cu-15Ni-8Sn by Two-Phase Heat Treatment

1982 ◽  
Vol 104 (3) ◽  
pp. 234-240 ◽  
Author(s):  
T. J. Louzon
Keyword(s):  
Heat Treatment ◽  
Single Phase ◽  
Phase Region ◽  
Two Phase ◽  
Heat Treated ◽  
Slow Kinetics ◽  
Increased Strength ◽  
Kinetics Of ◽  
Phase Solution ◽  
Strength And Ductility

A heat treatment has been developed which produces significant improvements in the tensile properties of Cu-15Ni-8Sn spinodal alloy. The treatment involves solution heat treatment in the two-phase region rather than the single-phase region normally used. After quenching and aging, increased strength and ductility of the alloy over single phase solution heat-treated and aged values were found. The mechanical properties obtained were superior to any previously observed for material of the compositions studied in the solution treated, quenched, and aged condition. Also, the alloys’ transformation kinetics were greatly slowed by the two phase heat-treatment. It is suggested that the increase in strength and slow kinetics of transformation observed are caused by grain size effects and by grain boundary modifications. Resistivity data and etching response corroborate these arguments.

Effect of Two-Phase Region Quenching Temperature on Microstructure Evolution and Microhardness of HSLA100 Steel

2012 ◽  
Vol 602-604 ◽  
pp. 380-384
Author(s):  
X. Yan ◽  
G.F. Zhou ◽  
C.M. Zhu ◽  
J.S. Guan
Keyword(s):  
Microstructure Evolution ◽  
Volume Fraction ◽  
High Strength ◽  
Phase Region ◽  
Two Phase ◽  
Quenching Temperature ◽  
Island Structure ◽  
Transmission Electron ◽  
Evolution Characteristics ◽  
Lath Bainite

The microstructure evolution characteristics and those effects on microhardness of HSLA (high strength low alloy) 100 steel secondary quenched in the two-phase region were investigated. The results show that the mixed microstructure of ferrite and the M-A（mastenite-austenite）islands can be obtained in the intercritical quenching region. A small amount of island structure distributing along the lath ferrite quenched at 700°C is observed by transmission electron microscope (TEM). With the quenching temperature increasing, the island structure increases in quantity and coarsens in shape, at the same time, the ferrite gradually transform from single lath morphology to polygonal shape with the dislocation density lowing. When quenched at 820°C, the microstructure reverts to lath bainite. There is a good correlation between Vickers hardness value and the volume fraction of martensite or bainite HSLA100 steel quenched in the two-phase region. The microhardness value of the steel continually increase from 240HV to 320HV quenched at the range of 700°C to 820°C, and then keep a very small fluctuation around 320HV when the temperature exceeds to 820°C.

STEM BSE imaging and Monte Carlo simulation of α-β microstructures in NbTi superconductors

1992 ◽  
Vol 50 (1) ◽  
pp. 86-87
Author(s):  
T. J. Headley ◽  
J. R. Michael ◽  
F. A. Greulich ◽  
M. J. Carr ◽  
J. M. Seuntjens
Keyword(s):  
Heat Treatment ◽  
Current Density ◽  
Volume Fraction ◽  
High Current Density ◽  
Cold Drawing ◽  
Final Heat Treatment ◽  
Two Phase ◽  
Final Heat ◽  
Pinning Properties ◽  
Image Analysis Techniques

High current density NbTi multifilamentary superconductors have α-β microstructures tailored by thermo-mechanical processing involving interspersed cold drawing and heat treatment. A final heat treatment in the two-phase α-β field controls the volume fraction of α-Ti precipitates and subsequent cold drawing refines the scale of the microstructure to a level that optimizes flux pinning properties which affect critical current density (Jc). The volume fraction, particle size, shape and spacing of α-Ti precipitates present after the final heat treatment are important parameters of interest, and should be measurable by image analysis techniques if suitable images were available.

Effect of Annealing Process on Microstructure and Tensile Properties of TC16 Titanium Alloy after Rapid Heat Treatment

2021 ◽  
Vol 1032 ◽  
pp. 152-156
Author(s):  
Peng Lei ◽  
Shu Cheng Dong ◽  
Guang Yu Ma ◽  
Tuo Cheng ◽  
O.M. Ivasishin
Keyword(s):  
Heat Treatment ◽  
Titanium Alloy ◽  
Tensile Properties ◽  
High Strength ◽  
Optical Microscope ◽  
Annealing Process ◽  
Test Machine ◽  
Two Phase ◽  
Reduction Of Area ◽  
Rapid Heat Treatment

TC16 titanium alloy is a martensite α+β two-phase high strength titanium alloy, which can improve its structure and enhance properties through heat treatment. Effect of annealing process on microstructure and tensile properties of TC16 titanium alloy was investigated using optical microscope, scanning electron microscope and universe tensile test machine. The results show that when annealed at 720°C for 4h then furnace cooling to ambient temperature, the tensile strength of the TC16 alloy reaches nearly 900MPa,the elongation reaches 19.6% and the reduction of area reaches 65%, which present a good comprehensive performance.

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