Microstructures and mechanical properties of 4 wt%TiB2/Al-Si-Cu-Zn (T6) composite thin-walled shell housing fabricated by high pressure die casting

Shuaiying Xi1, Guodong Ma1, Lu Li1,2, Yuanbo Zhang1, Xiangyang Yu1, Yongkun Li3 and Rongfeng Zhou1,2

Published 24 March 2021 • © 2021 The Author(s). Published by IOP Publishing Ltd
Materials Research Express, Volume 8, Number 3
Citation Shuaiying Xi et al 2021 Mater. Res. Express 8 036514

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

고압 다이캐스팅으로 제작 된 4 wt % TiB 2 / Al-Si-Cu-Zn (T6) 복합 박막 쉘 하우징의 미세 구조 및 기계적 특성

Abstract

The application demand of lightweight high-quality aluminum alloy parts in automotive and aerospace fields is increasingly. In aluminum matrix composites, reinforcing particles can significantly improve the performance of the matrix. In this paper, the microstructures and mechanical properties of die-cast 4 wt%TiB2/Al-9Si-3Cu-0.8Zn composite were systematically analyzed by x-ray diffraction, optical microscope, scanning electron microscopy, energy dispersive spectrometer, transmission electron microscopy and tensile testing. The composite was successfully fabricated from an Al-K2TiF6-KBF4 system by in situ melting technique. The research results show that the average grain sizes of the α-Al phase gradually decreased with the increase of filling distance. And the TiB2 particles were distributed around eutectic Si in irregular polyhedral morphology or nearly circular shape. Meanwhile, the crystal structures of Ti-B compound and long needle shaped nano-sized precipitated were identified and analyzed, and they were found to be TiB2 and Al2Cu phase, respectively. Tensile testing results show that the mechanical properties of die-cast composite clearly increase after T6 heat treatment. The yield strength, ultimate tensile strength and elongation could reach 311 MPa, 379 MPa and 2.8% respectively, with the best injection velocity (1.8 m s−1). The significantly enhancement of mechanical properties of composite after T6 heat treatment was mainly due to the introduction of TiB2 reinforcing phase and the precipitation of Al2Cu precipitate in the aging stage. The results implied that the introduction of TiB2 reinforced particles could improve the mechanical properties of die castings, which has an important guiding role for its practical application.

Korea

자동차 및 항공 우주 분야에서 경량 고품질 알루미늄 합금 부품에 대한 응용 수요가 증가하고 있습니다. 알루미늄 매트릭스 복합재에서 강화 입자는 매트릭스의 성능을 크게 향상시킬 수 있습니다. 

본 논문에서는 다이캐스트 4wt%TiB2/Al-9Si-3Cu-0.8Zn 복합체의 미세구조와 기계적 특성을 X선 회절, 광학 현미경, 스캐닝 전자 현미경, 에너지 분산 분광계, 전송 전자 현미경 및 인장 시험에 의해 체계적으로 분석하였습니다. 복합 재료는 현장 용해 기술에 의해 Al-K2TiF6-KBF4 시스템에서 성공적으로 제작되었습니다.

연구 결과에 따르면 α-Al 단계의 평균 곡물 크기는 충전 거리가 증가함에 따라 점차 감소했습니다. 그리고 TiB2 입자들은 불규칙한 다면체 형태학 또는 거의 원형에 가까운 형태로 유전자 Si 주변에 분포했습니다. 한편, Ti-B 화합물의 결정 구조와 긴 바늘 모양의 나노 크기의 침전물이 확인되고 분석되었으며, 각각 TiB2상 및 Al2Cu상인 것으로 확인되었습니다. 인장 테스트 결과, 다이캐스트 합성물의 기계적 특성은 T6 열처리 후 확실히 증가한다는 것을 알 수 있습니다.

항복 강도, 최종 인장 강도 및 연장은 최고 분사 속도(1.8 ms-1)로 각각 311 MPa, 379 MPa 및 2.8%에 이를 수 있습니다. T6 열처리 후 합성물의 기계적 특성이 크게 향상된 것은 주로 TiB2 강화 단계가 도입되고 노화 단계에서 Al2C 침전물이 침전했기 때문입니다. 결과는 TiB2 강화 입자의 도입으로 다이 주물의 기계적 특성이 개선될 수 있다는 것을 시사했습니다. 다이 주물의 기계적 특성은 실제 적용에서 중요한 지침 역할을 합니다.

Figure 1. Schematic diagram of (a) the preparation of 4 wt%TiB2/Al-9Si-3Cu-0.8Zn composite; (b) HPDC mold; (c)HPDC casting.
Figure 1. Schematic diagram of (a) the preparation of 4 wt%TiB2/Al-9Si-3Cu-0.8Zn composite; (b) HPDC mold; (c)HPDC casting.
Figure 2. Dimensions of the samples for tensile testing.
Figure 2. Dimensions of the samples for tensile testing.
Figure 3. XRD spectra of die-cast 4 wt%TiB2/Al-Si-Cu-Zn composite.
Figure 3. XRD spectra of die-cast 4 wt%TiB2/Al-Si-Cu-Zn composite.
Figure 4. TEM micrographs of TiB2 particles in the die-casting composite: (a) morphology of TiB2 in the Al matrix; (b) SAED pattern of the TiB2 in (a)
Figure 4. TEM micrographs of TiB2 particles in the die-casting composite: (a) morphology of TiB2 in the Al matrix; (b) SAED pattern of the TiB2 in (a)
Figure 5. TEM images of Al2Cu precipitates: (a) bright-field TEM image of the composite; (b) STEM image of the precipitates in the matrix; (c) HRTEM image between the Al2Cu precipitate and α-Al matrix; (d) FFT image of the region C in (c).
Figure 5. TEM images of Al2Cu precipitates: (a) bright-field TEM image of the composite; (b) STEM image of the precipitates in the matrix; (c) HRTEM image between the Al2Cu precipitate and α-Al matrix; (d) FFT image of the region C in (c).
Figure 6. Castings of the 4 wt%TiB2/Al-Si-Cu-Zn composite fabricated by the HPDC at different injection velocity: (a) 0.8 m s−1; (b) 1.16 m s−1; (c) 1.8 m s−1; (d) 2.5 m s−1; (e)–(h) filling ends of the castings (a)–(d).
Figure 6. Castings of the 4 wt%TiB2/Al-Si-Cu-Zn composite fabricated by the HPDC at different injection velocity: (a) 0.8 m s−1; (b) 1.16 m s−1; (c) 1.8 m s−1; (d) 2.5 m s−1; (e)–(h) filling ends of the castings (a)–(d).
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