Types And Uses Of Titanium Alloys|High Toughness|High Strength|Heat Treatment

Titanium alloys are alloys composed of titanium as the basis and other alloying elements. Titanium alloy can be divided into structural titanium alloy and heat-resistant titanium alloy, or α-type titanium alloy, β-type titanium alloy and α + β-type titanium alloy.

I. Development history of titanium alloy

Titanium is an important structural metal developed in the 1950s, and many people in the world have recognized the importance of titanium alloy materials, and have conducted research and development on them and obtained practical applications.

A practical titanium alloy is the United States in 1954, the successful development of Ti-6Al-4V alloy, because of its heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biocompatibility are better, and become a titanium alloy industry, the alloy has accounted for the use of all titanium alloys, 75% to 85%. Many other titanium alloys can be regarded as its modification.

Industrialized production of titanium was started in 1948. 1950s to 1960s, mainly the development of high-temperature titanium alloys for aircraft engines and structural titanium alloys for airframes, developed a number of corrosion-resistant titanium alloys in the 1970s, and corrosion-resistant titanium alloys and high-strength titanium alloys have been further developed since the 1980s. The use temperature of heat-resistant titanium alloy has been increased from 400℃ in the 1950s to 600～650℃ in the 1990s, so that titanium is used in the engine by the cold end of the engine (fan and compressor) to the hot end of the engine (turbine) direction. Structural titanium alloys to high strength, high plasticity, high strength and high toughness, high modulus and high damage tolerance direction.

Since the 1970s, shape memory alloys such as Ti-Ni, Ti-Ni-Fe, and Ti-Ni-Nb have also appeared and have gained increasingly wide application in engineering.

China began research on titanium and titanium alloys in 1956; industrialized production of titanium began in the mid-1960s and TB2 alloy was developed.
Second, the main classification of titanium alloy

Titanium has two kinds of homogeneous heterocrystals: titanium alloy titanium is a homogeneous isomer, melting point of 1668 ℃, in less than 882 ℃ was a dense row of hexagonal lattice structure, known as α-titanium; in 882 ℃ above the body-centered cubic lattice structure, known as β-titanium.

The use of titanium's different characteristics of the above two structures, add the appropriate alloying elements, so that the phase transition temperature and phase content gradually change and get different organizations of titanium alloys.

At room temperature, titanium alloys have three types of matrix organization, titanium alloys are also divided into the following three categories: α-alloys, (α + β) alloys and β-alloys. In China, these alloys are referred to as TA, TC and TB respectively.

Alpha titanium alloy

It is a single-phase alloy composed of α-phase solid solution, which is α-phase, stable organization, higher wear resistance than pure titanium, and strong oxidation resistance, both at general temperature and at higher temperature of practical application. Under the temperature of 500℃～600℃, it still maintains its strength and creep resistance, but it cannot be strengthened by heat treatment, and its room temperature strength is not high.

β Titanium Alloy

It is a single-phase alloy composed of β-phase solid solution, which has high strength without heat treatment, and further strengthened after quenching and aging, the room temperature strength can be up to 1372～1666MPa; however, it has poor thermal stability, and is not suitable to be used at high temperatures.

α+β titanium alloy

It is a dual-phase alloy with good comprehensive performance, good organizational stability, good toughness, plasticity and high-temperature deformation properties, good hot pressure processing, quenching, aging to make the alloy strengthened. After heat treatment, the strength is about 50% higher than the annealed state; high-temperature strength, can work for a long time at a temperature of 400 ℃ to 500 ℃, and its thermal stability is second to α titanium alloy.

Among the three kinds of titanium alloys, α-titanium alloy and α+β-titanium alloy are commonly used; α-titanium alloy has good machinability, α+β-titanium alloy is the second best, and β-titanium alloy is poor.