NGHIÊN CỨU SỰ HÌNH THÀNH TỔ CHỨC HỢP KIM TRÊN CƠ SỞ AlFeSi NGUỘI NHANH VỚI SỰ CÓ MẶT CỦA Mn VÀ ĐẤT HIẾM

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Tác giả: Thị Ngọc Quyên Hoàng, Minh Đức Lê, Hồng Hải Nguyễn, Ngọc Tiến Nguyễn, Quốc Tuấn Nguyễn

Ngôn ngữ: vie

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Thông tin xuất bản: Tạp chí Khoa học và Công nghệ - Đại học Thái Nguyên, 2024

Mô tả vật lý: tr.165 - 173

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Al-Si alloys are most used among Al alloys due to their good mechanical, as same as casting properties. The problem is the existence of very harmful b-Al5FeSi intermetallic compound, which should be replaced by less harmful Chinese script a-Al8Fe2Si or by more complicated and compact AlFeSiMn compound. So, the problem can be resolved by adding some elements such as Mn or rare earth metals or by high cooling rate. Thus, 1.5 kg material of composition as Si: 1.94%, Mn: 4.1%, Fe: 1.04%, Al al. is melted in a resistant furnace, degassed by Ar blowing into the melt for 2 minutes then poured into vacuum copper mold to prepare the specimens of the thickness 1, 3 and 6 mm to produce very high cooling rate, which can reach 103 K/s. With the presence of Mn the harmful Fe-containing phase, such as b-Al5FeSi, can be partly replaced by more compact 4-component intermetallic AlMnFeSi due to the fact that Fe-atoms can be substituted by Mn-atoms. High cooling rate depress the diffusion of Si from the melt to the Chinese script a-Al8Fe2Si and keep it stable at room temperature. Adding of rare earth can change the morphology of b-Al5FeSi phase to much finer by “poison” mechanism. As the results, the harmful b-Al5FeSi phase is completely absent or broken down into small debris, expecting to enhance the mechanical properties of alloys.Hợp kim Al-Si là loại hợp kim được sử dụng rộng rãi nhất trong các loại hợp kim Al do có cơ tính cũng như tính đúc tốt. Tuy nhiên sự tồn tại của pha liên kim b-Al5FeSi trong hợp kim này là rất có hại và cần được thay thế bởi pha a-Al8Fe2Si hình dáng chữ Trung Quốc ít có hại hơn hoặc bằng pha AlFeSiMn phức tạp hơn nhưng gọn hơn. Vấn đề có thể được giải quyết bằng cách bổ sung Mn hoặc các nguyên tố đất hiếm, hoặc bằng cách tăng tốc độ nguội. Để tiến hành thực nghiệm, 1,5 kg vật liệu có thành phần Si: 1,94%, Mn: 4,1%, Fe: 1,04%, Al al. được nấu trong lò điện trở, khử khí bằng cách thổi Ar trong vòng 2 phút, sau đó được rót vào khuôn đồng hút chân không để đúc các mẫu có chiều dày 1, 3 và 6 mm với tốc độ nguội cao, có thể lên tới 103 K/s. Với sự có mặt của Mn các pha liên kim chứa sắt có hại như b-Al5FeSi được thay thế một phần bởi pha liên kim 4 cấu tử AlMnFeSi do các nguyên tử Fe bị các nguyên tử Mn thay thế. Tốc độ nguội cao cản trở quá trình khuếch tán Si từ kim loại lỏng vào pha a-Al8Fe2Si chữ Trung Quốc và giữ nó ổn định ở nhiệt độ thường. Việc bổ sung các nguyên tố đất hiếm có thể làm thay đổi hình thái của pha b-Al5FeSi và làm cho chúng nhỏ mịn hơn rất nhiều nhờ cơ chế “đầu độc”. Kết quả là pha b-Al5FeSi có hại hoặc là hoàn toàn vắng mặt, hoặc bị vỡ vụn thành những mảnh nhỏ, hứa hẹn cải thiện đáng kể các tính chất cơ học của hợp kim.

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