A heat treatment study has been carried out on Al 7075 alloys. Al 7075 Alloys have strong, lightweight, corrosion-resistant, and good thermal conductivity properties. To meet the requirements of the Al-7075 alloy, a T6 heating process can be used. The T6 process begins with a heated solid solution at temperatures above 570 ° C held for 1 hour, then dip it quickly in water media, as well as the artificial aging process time variations of 1, 4, and 20 hours at a temperature of 210°C. After the cooling process, the specimen is then carried out in a metallographic process. Characterization of hardness by Vickers scale obtained that Al 7075 alloy without heat treatment gave a hardness rate of 84.1 HV. Al 7075 test sample in which heat treatment gave the highest hardness value of 144.90 HV obtained at a combination of the aging temperature of 210°C aging time of 20 hours, an increase in hardness value of 42.96%. The crystal structure test using Scanning Electron Microscope (SEM), showed that the Al 7075 test sample without heat treatment showed the dominant Al matrix, whereas in the Al 7075 test sample after going through the T6 process, the CuA12, AlCuMg, MgZn2 phases were used to harden the alloy. Crystal size, dislocation density, and crystal lattice strain with X-Ray Diffraction (XRD), indicate an increase in crystal size as the heating time of artificial aging increases. While the dislocation density and lattice strain increase during the artificial aging period of 1 hour and 4 hours, then at 20 hours experience a decrease in dislocation density and lattice strain.
Keywords: Al-7075 alloys, artificial aging, T6, hardness, Vickers, crystal structure, crystal size, dislocation density, lattice strain.
Abstrak
Telah dilakukan studi perlakuan panas terhadap paduan Al 7075. Paduan Al 7075 mempunyai sifat kuat, ringan, tahan korosi, dan konduktifitas termal yang baik. Untuk memenuhi syarat paduan Al-7075 dapat dipakai dilakukan proses pemanasan T6. Proses T6 dimulai dengan dipanaskan solid solution pada suhu diatas 570°C ditahan selama 1 jam, kemudian celup cepat di media air, serta proses penuaan buatan (artificial aging) variasi waktu 1, 4, dan 20 jam pada suhu 210°C. Setelah proses pendinginan, spesimen ini kemudian dilakukan proses metalografi. Karakterisasi kekerasan dengan skala Vickers, diperoleh bahwa paduan Al 7075 tanpa perlakuan panas memberikan angka kekerasan sebesar 84,10 HV. Sampel uji Al 7075 yang mengalami perlakuan panas memberikan nilai kekerasan tertinggi sebesar 144,90 HV diperoleh pada kombinasi temperatur aging 210°C waktu aging 20 jam, terjadi kenaikan nilai kekerasan sebesar 41,96%. Pengujian struktur kristal dengan Scanning Electron Microscope (SEM), menunjukkan bahwa pada sampel uji Al 7075 tanpa perlakuan panas terlihat matriks Al yang dominan, sedangkan pada sampel uji Al 7075 setelah melalui proses T6 memunculkan fasa CuA12, AlCuMg, MgZn2 yang berfungsi mengeraskan paduan. Ukuran kristal, kerapatan dislokasi, dan regangan kisi kristal dengan X-Ray Diffraction (XRD), menunjukkan bertambahnya ukuran kristal seiring dengan lamanya waktu pemanasan penuaan buatan. Sedangkan densitas dislokasi dan regangan kisi meningkat selama periode waktu pemanasan 1 jam dan 4 jam, lalu pada waktu 20 jam mengalami penurunan densitas dislokasi serta regangan kisi.
Kata Kunci: Paduan Al-7075, penuaan buatan, T6, kekerasan, Vickers, struktur kristal, ukuran kristal, kerapatan dislokasi, regangan kisi.
Retrogression and re-aging of AL-7075 Microstructure and Corrosion Behavior Characterization