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Stamping forming ability of different types of titanium alloy

Nov 09, 2018

Stamping forming ability of different types of titanium alloy

Titanium alloys are classified according to the phase structure and the content of β-stabilizing elements in a metastable state. Titanium alloys are classified into three types: α-type, α+β-type and β-type.

The α-type titanium alloy usually contains only the α phase at room temperature, and the α phase belongs to the close packed hexagonal (HCP) structure. This structure determines its deformation at room temperature, and is different from the body-centered cubic structure, and the close-packed hexagonal structure slip system is more Less, and varies with the ratio of the c-axis to the a-axis. Pure titanium has a c/a of 1.579, the main slip system is pagenumber_ebook=8, pagenumber_book=16, which is cylinder slip, in addition to pagenumber_ebook=8, pagenumber_book=16, pagenumber_ebook=8, pagenumber_book=16 slip system, There are only four completely independent slip systems in these slip systems, which do not reach the five slip systems necessary for plastic deformation required by Mises conditions. However, due to the action of twin crystal {1122}, {1121} and pagenumber_ebook=8, pagenumber_book=16, the deformation ability of the α-type titanium alloy is strong due to the plastic deformation process. Therefore, the α-type titanium alloy is suitable for room temperature stamping. Such titanium alloys include TA1, TA2, TA3 and the like.

The α+β type titanium alloy has an annealed structure of α+β phase (primary α phase + residual β phase), and the β phase content is generally 5% to 40%. The α-β-type titanium alloy is simultaneously added with an α-stabilizing element and a β-stabilizing element, so that both the α phase and the β phase are strengthened. Although the β phase belongs to the body-centered cubic structure, there are many slip systems that can be activated during the room temperature deformation process, but since the primary α phase is obtained by appropriate heat treatment after large deformation in the two-phase region, it is between the residual β phase and the residual β phase. The Burgers orientation relationship has been destroyed. At this time, the primary α phase and the residual β phase belong to a non-coherent relationship, and the slip orientations in the primary α phase and the residual β phase are randomly assigned; in addition, due to the primary α phase and residual β At the interface (α/β), the lattice parameters on the two sides are different, the interface energy is high, and the coordination during the deformation process is poor. Therefore, the room temperature strength of the α+β type titanium alloy is higher. It is mainly suitable for aerospace structural parts, etc. It is not suitable for stamping at room temperature. Commonly used α + β type titanium alloys include TC4, TC6, TC11 and TC21.

The beta titanium alloy typically comprises a metastable beta titanium alloy and a stabilized beta titanium alloy. Due to the large specific gravity of the stable β-type titanium alloy, the difficulty in melting, and the large deformation resistance, the titanium alloy is currently used less. The metastable β-type titanium alloy contains a β-stabilizing element higher than the critical concentration, and almost all of the metastable β phase can be obtained by air cooling or water quenching. The metastable β phase belongs to the body-centered cubic structure (BCC), and the metastable β phase slip direction is <111>, and the slip surfaces that may appear are {110}, {112}, {123}, if three sets of slips The surface can be activated, and the number of potential slip systems is 48, of which {110}<111> slip system is 12; {112}<111> slip system is 12, {123}<11l> There are 24 slip systems. Therefore, the metastable β-type titanium alloy has very good process plasticity and cold formability in an annealed or solid solution state. These alloys mainly include TB2, TB3, TB5 and TB8. They usually have excellent cold rolling and cold formability, can form moderately complex sheet metal parts at room temperature, and can be used for cold rivets and bolts.

In summary, the α-type titanium alloy can be coordinated by twinning, and the metastable β-type titanium alloy β phase belongs to the body-centered cubic structure, and there are many slipping systems that can be actuated, and they are good stamping forming materials.

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