TENTANG TITANIUM

Paduan Titanium: Sejarah, Struktur, dan Klasifikasi

Titanium alloys were originally developed in the early 1950s for aerospace applications due their unusually high strength-to-density ratio, meaning, they are light, yet strong. Nowadays, though they are still vital to the aerospace industry for the exactly the same properties, the recognition of titanium’s excellent resistance in highly corrosive environments has led to widespread non-aerospace industrial applications. Stemming from decreasing cost and increasing availability of mill and fabricated products, titanium alloys have become standard engineering materials for a host of common consumer products too.

Titanium Structure

In order to better understand the composition of an alloy containing titanium, you first need to understand the common titanium structure. Titanium atoms are arranged in regular patterns, extending in all three dimensions. The shape of these patterns determine two possible forms for pure titanium:

α (alpha)-titanium – in which atoms are arranged in a somewhat hexagonal pattern, and,

β (beta) -titanium – in which atoms are arranged in a cubic (square) pattern;

Pure titanium atoms are arranged as of α-phase at temperatures up to1621°F (883°C). When this temperature (Beta Transus Tempereture) is reached they transform in β-phase.

TI alloys are classified according to the alloying elements that may stabilize either α-phase or β-phase of titanium.

Aluminum (Al), gallium (Ga), Nitrogen (N), Oxygen (O) stabilize α-phase.

Molybdenum (Mo), vanadium (V), tungsten (W), tantalum (Ta), silicon (Si) stabilize β-phase.

Commercially pure titanium consist mainly of α-phase and some dispersed β-phase. There are five titanium grades of what is known as commercially pure (CP) or unalloyed titanium – ASTM Grades 1 through 4, and 7. Each grade has a different amount of impurity content, with Grade 1 being the most pure. Usually, titanium jewelry is made of Grade 2.A special note is to be made for the black titanium alloy, which is a special patented alloy used in the jewelry industry, especially in wedding bands.

Titanium alpha and near-alpha alloys consist entirely of α-phase. They contain aluminum as the major alloying element, stabilizing α-phase. Alpha alloys do not generally respond to heat treatment, but they are weldable and are commonly used for cryogenic applications, airplane parts, and chemical processing equipment.

3. Paduan Alfa-Beta ($\alpha$–$\beta$)

Mengandung 4-6% penstabil fase-$\beta$; oleh karena itu, mereka terdiri dari campuran fase $\alpha$ dan $\beta$. Paduan titanium $\alpha$–$\beta$ dapat diberi perlakuan panas. Mereka memiliki kekuatan mekanik yang tinggi dan kemampuan bentuk panas yang baik. Paduan ini dapat diperkuat melalui perlakuan panas dan penuaan (aging), sehingga proses manufaktur dapat dilakukan saat material masih lunak (ductile), kemudian diberi perlakuan panas untuk memperkuat material tersebut—ini merupakan keuntungan besar. Paduan ini digunakan pada suku cadang pesawat dan turbin pesawat, peralatan pemrosesan kimia, perangkat keras kelautan, dan perangkat prostetik.

Ti-6Al-4V adalah paduan titanium $\alpha$–$\beta$ yang paling populer—total produksinya mencakup sekitar setengah dari semua paduan TI. Aluminium (Al) ditambahkan sebagai penstabil fase-$\alpha$ dan pengeras, sementara Vanadium (V) menstabilkan fase-$\beta$ yang ulet, memberikan kemampuan pengerjaan panas pada paduan tersebut.

4. Paduan Beta ($\beta$)

Paduan ini kaya akan fase-$\beta$ dan merupakan kelompok terkecil dari semuanya. Mereka memiliki kemampuan pengerasan yang baik, kemampuan bentuk dingin yang baik saat melalui proses solution-treated, dan kekuatan tinggi saat melalui proses penuaan. Paduan beta sedikit lebih padat daripada paduan titanium lainnya. Mereka digunakan untuk tugas yang lebih berat pada pesawat terbang, komponen kedirgantaraan, pengencang (fastener) berkekuatan tinggi, batang torsi, lembaran pesawat berkekuatan tinggi, dan bagian mesin pesawat yang tahan bakar.

Aplikasi Khusus Lainnya

  • Baja Maraging: Paduan besi khusus di mana titanium menjadi komponen kritis, meskipun titanium bukan konstituen utamanya.

  • NITINOL: Titanium juga merupakan bagian dari paduan pengingat bentuk (shape memory alloy) yang paling banyak digunakan ketika bergabung dengan nikel.

Lihat berbagai spesifikasi standar internasional dan spesifikasi titanium yang setara di sini.

About Titanium