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共晶铝硅合金的单变质及复合变质处理研究
论文作者:童鞋论文网  论文来源:www.txlunwenw.com  发布时间:2019/9/20 8:34:44  

摘要:采用Al–5Ti中间合金对共晶铝硅合金进行变质处理,研究结果表明:当变质温度由650 °C提高700 °C时,初生α–Al面积分数急剧增加,而温度从700 °C提高750 °C时,初生α–Al面积分数增加较少。当变质处理温度为700 °C时,共晶铝硅合金中初生α–Al相和共晶Si最为细化。随着Al–5Ti加入量增加,共晶铝硅合金中初生α–Al的面积分数呈现出先增大后减小的变化规律,当加入0.2 wt.% Al–5Ti时,合金组织中初生α–Al相面积分数最大。与未变质共晶铝硅合金相比,700 °C经0.2 wt.% Al–5Ti变质合金的抗拉强度和伸长率分别提高了17%和42%。

采用Al–3P中间合金对共晶铝硅合金进行变质处理,研究结果表明:当Al–3P加入量一定时,在740 °C变质后共晶铝硅合金中初晶Si和α–Al的面积分数最大。随着Al–3P加入量的增大,初晶Si和α–Al相面积分数呈现先增大后减小的变化趋势,初晶Si的尺寸不断减小。当Al–3P加入量为0.4wt.%时,初晶Si和α–Al相面积分数最大。与未变质共晶铝硅合金相比,740 °C经0.4 wt.% Al–3P变质合金的抗拉强度和伸长率分别提高了7%和74%。

采用Al–3P和Al–3B中间合金对共晶铝硅合金进行复合变质处理,研究结果表明:随着Al–3B加入量的增多,经0.4 wt.% Al–3P变质共晶铝硅合金中初生α–Al相面积分数呈先增大后减小的趋势,初晶Si面积分数和尺寸则呈现先迅速减少然后趋于稳定的趋势。经Al–3P和Al–3B复合变质后,共晶铝硅合金中的共晶Si从针片状转变为细小的短杆状或颗粒状。与Al–3P单变质共晶铝硅合金相比,经0.4 wt.% Al–3P和0.2 wt.% Al–3B复合变质处理后,共晶铝硅合金综合力学性能得到明显改善。

采用平衡合金法测定了Al–B–P三元系700°C等温截面相关系,并基于该相图设计了Al–1.5B–3P中间合金对共晶铝硅合金进行了复合变质处理。研究结果表明,Al–B–P三元系相图700 °C等温截面包含5个三相区:Liq.+AlB2+AlP,AlB2+AlP+BP,AlB12+AlB2+BP,AlB12+BP+B,AlP+BP+Pgas。Al–1.5B–3P中间合金的相组成为Al、AlB2和AlP相,经该中间合金复合变质处理后,共晶铝硅合金中出现大量细小的初生α–Al枝晶和细小圆整且均匀分布的初晶Si,共晶Si由针片状转变为颗粒状或短杆状。与未变质的共晶铝硅合金相比,采用0.4 wt.%Al–1.5B–3P变质处理后,共晶铝硅合金的抗拉强度和伸长率分别提高了20%和24%。

Modification of eutectic Al–Si alloys withAl–5Ti master alloy was studied. The results show that when the modificationtemperature increased from 650 °C to 700 °C, the fraction of primary α–Al ineutectic Al–Si increased sharply. Then, the fraction of primary α–Al increasedslowly with increasing temperature from 700 °C to 750 °C. The primary α–Al andeutectic Si in eutectic Al–Si were finest, when the alloy was modified at 700°C. The fraction of primary α–Al in eutectic Al–Si first increased and thendecreased with increasing the added amount of Al–5Ti. The fraction of primaryα–Al in eutectic Al–Si was largest when the added amount of modifier was 0.2wt.%. Compared to the unmodified eutectic Al–Si alloy, the tensile strength andelongation of the alloy modified with 0.2 wt.% Al–5Ti at 700 °C increased by17% and 42%, respectively.

Modification of eutectic Al–Si alloys withAl–3P master alloy was studied. The results show that the fraction of primarySi and α–Al in eutectic Al–Si alloy were largest after modification at 740 °Cwhen a certain amount of Al–3P was added. The fraction of primary Si and α–Alin Al–Si eutectic alloy first increased and then decreased with increasingamount of Al–3P, and reached maximum when the added amount of Al–3P was 0.4wt.%. The size of the primary Si decreased continuously. Compared to theunmodified Al–Si eutectic alloy, the tensile strength and elongation of thealloy modified with 0.4 wt.% Al–3P at 740 °C increased by 7% and 74%,respectively.

Complex modification of eutectic Al–Sialloys with Al–3P and Al–3B was studied. The results show that the fraction ofα–Al in eutectic Al–Si alloy modified with 0.4 wt.% Al–3P first increased andthen decreased with increasing amounts of Al–3B, while the fraction and size ofprimary Si decreased rapidly first and then stabilized. The morphology ofeutectic Si transformed from needle–like into fine short rods or granules aftercomplex modification with Al–3P and Al–3B. The comprehensive mechanicalproperties of eutectic Al–Si alloy modified with 0.4 wt.% Al–3P and 0.2 wt.%Al–3B were improved compared with that of the alloy modified with Al–3P.

The 700 °C isothermal section of Al–B–Pternary system was studied by equilibrium alloy method. The eutectic Al–Sialloy was modified with the Al–1.5B–3P master alloy designed basing on thisphase diagram.

关键词:共晶铝硅合金;变质处理;显微组织;力学性能;Al–B–P三元系

Eutectic Al–Si alloy;Modification;Microstructure;Mechanical properties;Al–B–P ternary system

上一篇:晶体硅太阳能电池钝化接触技术研究     下一篇:低氧压铁基合金选择性氧化及相关相平衡研究
 
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