论文部分内容阅读
通过场发射扫描电镜装载原位拉伸台,对不同凝固条件下工业铸造A357铝合金进行原位拉伸试验。结果表明,裂纹微裂纹首先萌生于组织中破裂的共晶硅处,近邻的微裂纹连接形成小裂纹;多处形成的小裂纹彼此连接并形成较长裂纹,沿共晶区深化和扩展,逐渐发展为主裂纹;当主裂纹遇到铝基体时,扩展受阻,裂纹发生钝化并在其前沿区域形成剪切带;剪切带深化并开裂,主裂纹沿着深化的剪切带穿过基体继续扩展,最终导致试样断裂。A357铝合金的断裂方式为兼具韧性断裂和解理断裂的混合断裂。反重力铸造有效地改善合金微观组织形态,提高了合金的力学性能。
In-situ tensile test was carried out by field emission scanning electron microscopy (TEM) and in-situ tensile test of industrial cast A357 aluminum alloy under different solidification conditions. The results show that the crack microcracks first originate from the cracked eutectic silicon in the structure, and the adjacent microcracks are connected to form small cracks. The small cracks formed at various locations are connected to each other and form long cracks, which are deepened and extended along the eutectic area and gradually Developed as the main crack; when the main crack encounters the aluminum matrix, the expansion is hindered, the crack is blunted and a shear band is formed in the frontal region; the shear band deepens and cracks, and the main crack continues through the substrate along the deepened shear band Expansion, eventually leading to specimen fracture. A357 aluminum alloy fracture mode is both ductile fracture and cleavage fracture mixed fracture. Anti-gravity casting can effectively improve the microstructure of the alloy and improve the mechanical properties of the alloy.