【摘要】 探讨了Al—P中间合金对共晶及过共晶Al—Si合金的变质特点,P在Si相中的存在形式、分布规律及变质机制,实验表明,Al—P中间合金可有效地细化过共晶Al—Si合金中的初晶Si,使该合金的σb,20℃和δ20℃分别提高19.0％和125％。对共晶型Al—Si合金而言,Al—P中间合金可促使析出细小的初晶Si,获得过共晶型组织,并将针片状的共晶Si变为短杆状,从而使该材料的σb,20℃和σb,300℃分别提高11.1％和18.9％。Al—P中间合金加入到过共晶Al—Si合金中,P主要以AlP形式存在于初晶Si内部;加入到共晶Al—Si合金中的P分别以AlP和原子态P存在于Si相内。P对过共晶Al—Si合金变质是以AlP异质形核机理为主;而P对共晶Al—Si合金的变质是以AlP异质形核和原子态P影响Si相形态两种机制共同作用的结果。更多还原

【Abstract】 A new type of Al-2.5%P master alloy has been developed, which can be used to modify eutectic and hypereutectic Al-Si alloys. The modifying performance, the P distribution inside Si phases and modification mechanisms were investigated. It has been found that the Al-P master alloy can remarkably refine primary Si grains in hypereutectic Al-Si alloy and its σ_b,20℃ and δ_20℃can increase by 19.0% and 125% respectively; σ_b,20℃ and σ_b,300℃ of modified eutectic Al-Si alloy can increase by 11.1% and 18.9% respectively as result of the appearance of fine primary Si grains and shorter eutectic Si crystals. AIP particles are easily found in the center of some primary Si phases in treated hypereutectic Al-Si alloy, while AIP and dissociative P are observed in Si phase in modified eutectic Al-Si alloy. It is considered that there are two modification mechanisms for eutectic Al-Si alloy, one is heterogeneous nucleation and refining of primary Si phase by AlP particles, and the other is P atoms modify the morphologies of Si phases. The modification for the hypereutectic Al-Si alloy mainly depends on heterogeneous nucleation mechanism induced by AlP particles.更多还原