The primary purpose of microstructure control is to control the size of α grains. The desired α-grain size can be obtained by adjusting properly the heat treatment temperature and time. Fe added to the sheet together with oxygen for increasing the sheet strength is an element which helps stabilizes β phase.
Full Answer
How does grain size affect the mechanical properties of pure titanium?
The grain size has a significant effect on the mechanical properties of pure titanium. A greater deformation coordination ability caused by small initial grains results in higher yield strength.
How to control the α-grind size of commercially pure Titani-um sheets?
We simulated the growth of grains in commercially pure titani- um sheets. In many cases, they are manufactured and used in an α-phase region. The primary purpose of microstructure control is to control the size of α grains. The desired α-grain size can be obtained by adjusting properly the heat treatment temperature and time.
How to strengthen titanium alloy heat treatment?
Quenching aging is the main way to strengthen titanium alloy heat treatment, using phase change to produce strengthening effect, which is also known as heat treatment strengthening.
Does pinning effect affect grain growth in titanium and stainless steels?
Grain growth simulations of titanium and stainless steels have been performed using phase-field model. In the simulation of Ti-rich Ti-Fe-O ternary alloys modeling commer- cially pure titanium, it was shown that a grain growth is suppressed by the pinning effect by β grains in thermal equilibrium.
Does heat treatment reduce grain size?
Grain Size Effect: It has long been known that the properties of some metals could be changed by heat treating. Grains in metals tend to grow larger as the metal is heated. A grain can grow larger by atoms migrating from another grain that may eventually disappear.
Can pure titanium be heat treated?
While pure titanium is soft and relatively weak, heat treating can significantly enhance its properties. Titanium and titanium alloys are heat treated in order to: Reduce residual stresses from fabrication (stress relieving)
Does heat treatment increase grain size?
The average grain size increased with heat treatment from <0.5 to ∼10 μ-m. Phase analyses revealed predominantly tetragonal and cubic phases below 1750°C, with a significant decrease in tetragonal content and increase in monoclinic content for temperatures >1750°C.
What is the grain size of titanium?
Annealing at 500 °C significantly changed the microstructure of the nanocrystalline titanium. The grain size increased significantly, to an average value of 1.4 μm. Some grains even exceeded 3 μm in diameter.
How do you heat treat titanium?
Solution Treatment and Aging This process consists of heating to a specified temperature for the alloy, quenching at a controlled rate in either oil, air or water, and aging. Aging consists of reheating to a temperature between 425 and 650°C (800 to 1200°F) for approximately two hours.
Can you temper titanium?
Tempering. When titanium is quenched from an elevated temperature, reheated to a temperature below the beta transus, held for a length of time and again quenched, it is said to have been tempered. Three variables exist in tempering: the phases present, the time held, and the tempering temperature.
How do you control grain size?
It can be controlled by cold treatment, cold rolling, adding alloying but not substantially otherwise phase may change and CCT will change. Best way to reduce the grain size specially after diamond polishing put to the percholoric acid at low temperature and very low voltage for 30minutes to gallows.
What factors control the grain size of a metal?
Popular Answers (1) According to kinetics, time and temperature are two factors that affect the grain growth. But increasing temperature is much more effective than increasing time.
What causes large grain size?
Control of Grain Size Larger grains reduce the strength and toughness of the material, and grains can grow for various reasons. For example, if the material is left at above recrystallization temperature for too long, the grains increase in size as diffusion occurs across the grain boundaries.
What are the mechanical properties of commercially pure CP Ti?
Titanium - Commercially Pure (CP) Properties (Theoretical)Molecular Weight47.86 (Note: all properties listed are for bulk titanium metal)Tensile Strength140 MPaThermal Conductivity21.9 W/(m·K) @ 298.2 KThermal Expansion8.6 µm·m-1·K-1 (25 °C)Vickers Hardness830–3420 MPa13 more rows
What is titanium stainless steel?
Titanium-coated stainless steel can come in heavy gauge sheets because it is a thin layer of titanium chemically bonded with a thicker layer of stainless steel. Stainless steel coated with titanium may increase its scratch and corrosion resistance, making its durability superior to many other metal options.
How to heat treat titanium?
Titanium and titanium alloys are heat treated in order to: 1 Reduce residual stresses developed during fabrication (stress relieving) 2 Produce an optimum combination of ductility, machinability, and dimensional and structural stability (annealing) 3 Increase strength (solution treating and aging) 4 Optimize special properties such as fracture toughness, fatigue strength, and high-temperature creep strength.
What temperature does titanium creep straighten?
Creep straightening may be readily accomplished during the annealing and/or aging processes of most titanium alloys. However, if the annealing/aging temperature is below about 540 to 650°C (1000 to 1200°F), depending on the alloy, the times required to accomplish the desired creep straightening can be extended.
Why is titanium annealed?
The annealing of titanium and titanium alloys serves primarily to increase fracture toughness, ductility at room temperature, dimensional and thermal stability, and creep resistance. Many titanium alloys are placed in service in the annealed state.
What stabilizers lower the -to- transformation temperature?
Beta stabilizers, such as manganese, chromium, iron, molybdenum, vanadium, and niobium, lower the α-to-β transformation temperature and, depending on the amount added, may result in the retention of some β phase at room temperature. Alloy Types. Based on the types and amounts of alloying elements they contain, titanium alloys are classified as α, ...
What must be near a specified maximum to meet strength levels in solution treated and aged Ti-6Al-4 V?
It should be realized that: Oxygen and iron must be near specified maximums to meet strength levels in certain commercially pure grades. Oxygen must be near a specified maximum to meet strength levels in solution treated and aged Ti-6Al-4 V. Oxygen levels must be kept as low as possible to optimize fracture toughness.
Does titanium need heat treatment?
In addition, not all heat treating cycles are applicable to all titanium alloys, because the various alloys are designed for different purposes.
Is titanium an allotropic material?
Unalloyed titanium is allotropic. Its close-packed hexagonal structure (α phase) changes to a body-centered cubic, structure (β-phase) at 885°C (1625°F), and this structure persists at temperatures up to the melting point.
Most recent answer
Increasing temperature is more effective than increasing time get larger grain size in sintered samples. Initial size and distribution is also important in predicting the final size after sintering. To control the grain size various additions can be made to the starting powder to control the grain size at a particular sintering temperature.
Popular Answers (1)
According to kinetics, time and temperature are two factors that affect the grain growth. But increasing temperature is much more effective than increasing time.
All Answers (8)
Prolonged heat treatment is a solution for grain size increment in metals. For ceramics this phenomenon is rather longer, but possible.
When titanium alloy is heated above the transformation temperature, the crystal grains grow rapidly.?
When titanium alloy is heated above the β transformation temperature, the crystal grains grow rapidly. In the subsequent cooling, the α phase nucleates and grows on the grain boundary first, and grows into the inside of the grain.
Why is segmented heating used in titanium?
Therefore, it is recommended to adopt the method of segmented heating to minimize the thermal stress inside the ingot or billet.
How is titanium alloy determined?
The structure of titanium alloy is determined by thermal deformation , and heat treatment mainly only plays a role of adjustment . For example, heat treatment can only adjust the ratio of α phase and β phase obtained by thermal deformation, and the sheet structure produced by overheating cannot be changed into a dual-state structure by heat treatment.
Why is titanium alloy important?
Titanium alloy is favored by people for its excellent room temperature and high-temperature mechanical properties, outstanding corrosion resistance, and high strength. It has become an important structural material in the aviation and aerospace industries. The heat treatment of titanium alloy can significantly increase the strength ...
Can titanium be heated before forging?
Moreover, the method of heat treatment cannot eliminate the coarse-grained structure of the titanium alloy, and the forging deformation must be used to change the structure. Therefore, when heating before forging or heat treatment in the β zone, the heating temperature and time should be strictly controlled to prevent excessive grain growth.
Where is Advanced Refractory Metals located?
Headquartered in Lake Forest, California, USA, Advanced Refractory Metals (ARM) is a leading manufacturer & supplier of refractory metals across the world, providing customers with high-quality ...
Can titanium be strengthened?
Most near-α-type and stable β- type titanium alloys (except for a very small number such as Ti-2Cu alloy) cannot be strengthened by heat treatment, and only α+β-type titanium alloys can be strengthened by heat treatment.
What are the two phases of titanium?
In general, the organization of titanium alloys has two basic phases: α-phase and β-phase. The mechanical properties of titanium alloys largely depend on the proportion, morphology, size and distribution of these two phases.
What is the purpose of annealing titanium?
Annealing is suitable for various titanium alloys, and its main purpose is to eliminate stress, improve alloy plasticity and stabilize the structure. The forms of annealing include stress relief annealing, recrystallization annealing, double annealing, isothermal annealing and vacuum annealing, etc.
What makes titanium alloy brittle?
Formation of the ω phase will make titanium alloy brittle, the correct choice of the aging process (such as the use of a higher aging temperature) can make the ω phase decomposition. (3) It is difficult to refine titanium alloy grains using repeated phase transformations. This is also different from steel materials.
What is deformation heat treatment?
Deformation heat treatment is an effective combination of pressure processing (forging, rolling, etc.) and heat treatment technology, which allows both deformation strengthening and heat treatment strengthening to obtain organization and comprehensive performance that cannot be obtained with a single strengthening method.
What is the purpose of the repeated phase transformation of austenite and pearlite?
Most steels can use the repeated phase transformation of austenite and pearlite (or ferrite, cementite) to control the nucleation and growth of new phases to achieve the purpose of grain refinement. There is no such phenomenon in titanium alloys. (4) Poor thermal conductivity. Poor thermal conductivity can lead to the poor hardenability ...
Does titanium absorb hydrogen?
At the same time, titanium alloys tend to absorb hydrogen during heat treatment, causing hydrogen embrittlement.
Can titanium alloys be treated with heat?
Moreover, the method of heat treatment for pure a-type titanium alloys is basically ineffective, i.e., the heat treatment of titanium alloys is mainly used for α+β-type titanium alloys. (2) Heat treatment should avoid the formation of ω phase. Formation of the ω phase will make titanium alloy brittle, the correct choice of the aging process ...
Abstract
The grain size effect on deformation twinning behavior of pure titanium during uniaxial compression was investigated using electron backscattered diffraction (EBSD) technology. In this work, EBSD statistical analyses on big data sets of twins in pure titanium specimens with different initial grain sizes were carried out.
1. Introduction
It is well known that twinning plays a significant role during plastic deformation of titanium, especially at low temperature [ 1, 2 ].
2. Experimental
In the present study, the as-received material was a hot rolled 99.999% pure Ti sheet with a thickness of 12 mm. Cuboid specimens with dimensions of 9 mm × 8 mm × 7 mm (RD × TD × ND) were machined from the pure Ti sheet. Here, RD, TD, and ND represent the rolling direction, transverse direction, and normal direction, respectively.
3. Result
Fig. 3 shows the stress-strain curves of the ND-80% and RD-80% specimens with different grain sizes. The data suggests that the yield stresses of the ND specimens were higher than the RD specimens, which can be attributed to the different deformation mechanisms.
4. Discussion
The nucleation and growth of twins can be revealed by the statistical analysis of the number of twin lamellae, the twin volume proportion and the twin boundary length per unit area. The number of twin lamellae per grain reflects twin nucleation to some extent. as displayed in Fig. 12.
5. Conclusions
In this paper, the initial grain size effect on the twinning behavior of pure titanium during uniaxial compression was investigated by EBSD technology. Primary twinning, secondary twinning and twin-twin interactions were the focus of this research. The main conclusions can be summarized as follows:
CRediT authorship contribution statement
Bingshu Wang: Writing – original draft, preparation, Conceptualization, Methodology, Supervision. Huimin Liu: Investigation, Data curation. Yonggan Zhang: Validation, Visualization. Baoxue Zhou: Investigation, Data curation. Liping Deng: Validation, Writing – review & editing. Chen Wang: Resources. Junfeng Chen: Resources. Yonghao Zhang: Resources.
What temperature does hypereutectoid steel need to be heated?
Thus, most of the heat treatments (except normalising) of hyper-eutectoid steels are carried out by austenitisation at just above A 1 temperature, where the austenite grain size is minimum though complete austenitisation does not take place there.
How is ferrite grain size determined?
In as-hot rolled steels, the ferrite grain size is generally determined by the temperature at last pass of rolling (hot), which is subject to wide variation.
What temperature does austenite finish?
Normally, the austenitising temperature of many finishing heat treatment does not exceed 980°C. The fine grained steels are thus, able to retain a fine austenite grain size even in long carburising cycles, where the coarse grained steels might coarsen considerably.
What is normalising steel?
Normalising is the process of heating the steel to a low temperature in the austenite region, holding for a period long enough to attain temperature uniformly, that is, a uniform homogeneous austenite and then, air cooling.
Why is deoxidation important in steel?
The state of deoxidation of steel, hence, is important in the production of grain size controlled steels and only a minimum amount of reactive oxygen should be left in the bath so as to prevent excessive formation of alumina and its entrapment in solid steel (as non-metallic inclusions).
What phase is steel heated in?
The cooling may be rapid, even by water sprays and the cycle may be repeated. In practice, an alloy steel plate is first heated in the three phase region of austenite + ferrite + carbide in a normal gas-fired furnace (preheating). Each phase restricts the growth of others.
What are ultra fine grains?
In recent years, ultra-fine grains have been obtained in micro-alloyed steels having small amounts of strong carbide-forming elements such as Nb, V or Ti, though Nb in amount about 0.05% is preferred over others, because of its low solubility in steels . These elements show decrease of solid-solubility in austenite with the fall of temperature.