Series of Aluminium-Phosphorus Master Alloys (PDF)

(Project of Innovation Fund for Technology-Based Firms of Ministry of Science and Technology of China, Second-class invention prize of Ministry of Education of China, National invention patents)

1. Application

 1) It can be used to modify the microstructures of near-eutectic Al-Si alloys and to refine the primary Si in hypereutectic Al-Si alloys with 13-70wt%Si containing. For near-eutectic Al-Si alloys (e.g. alloys for piston application) modified by Al-P master alloy, large number of primary Si would precipitate, so the modified Al-Si alloys have the advantages of higher strength, better wear resistance and corrosion resistance, excellent volume stability as well as lower linear coefficient of thermal expansion. For hypereutectic Al-Si alloys refined by Al-P master alloy, the sizes of primary Si can be reduced to less than 30μm, and the morphology can be modified from plate-like to block-like. Furthermore, the mechanical properties can be improved dramatically.
  2) It can be used to modify and refine the primary Mg2Si in Mg-Si and Al-Mg-Si alloys. The morphology of primary Mg2Si can be modified from bulky dendrites to fine block-like, and the tension properties can be improved remarkably.
  3) It can be used to refine the primary Si in Cu-Si alloys with 12-60wt%Si containing.

2. Background 

 P modification has been widely used in Al-Si alloys, and P is added mainly in the form of red phosphorus, phosphate salt and Cu-P master alloys. But there are certain disadvantages for these additives.

 Red Phosphorus: The burning point is very low (about 240°C), so it is unsafe for transportation, preservation and application. Moreover, during the modification process, the melt reaction is very severe and toxic gas P2O5 will form and release, which induces serious environment pollution and equipments corrosion, and most importantly, does harm to the workers’ health. Furthermore, the P recovery is low in melt and difficult to control.
  Phosphate Salt: During the modification process, the toxic gas P2O5 will also release, which induces serious environment pollution. Lots of reaction slag which induces the corrosion of furnace lining will form. It is difficult to separate the slag from the aluminum melt, so the consumption of aluminum increases. Furthermore, the absorption of P is closely related to technical conditions and the skills of operators, so the modification efficiency is not stable.
  Toxic gas P2O5 which induces environment pollution will release during the application of red phosphorus and phosphate salt, P2O5 can erode skin, eyes and respiratory tract and can cause respiratory tract diseases. In addition, P2O5 could react with H2O which forms acid rains leading to the environmental deterioration.
  Cu-P master alloy: It is difficult to be melted because of its higher melting point, and it tends to segregate due to higher density. The modification efficiency is unstable and it is not applicable to be used in holding furnace without stirring.

 So it is imperative to prepare a new type of modifier without above disadvantages. With the support of Ministry of Education and Ministry of Science and Technology of China, a new environmentally friendly Al-P master alloy has been successfully developed after eight years’ efforts and technical innovation of our company, including binary AlP master alloy, ternary AlSiP master alloy and ternary AlCuP master alloy. Nowadays, Al-P master alloy has been used widely in many large and medium piston manufacturers and die casting factories, and it has also been exported to many foreign engine parts manufacturing enterprises in South Korea, India, USA and Malaysia, etc.

3. Characteristics

 The microstructure characteristic is that a large number of pre-generated AlP particles distributed in the Al-P master alloys. Compared with the current modifiers, the merits of Al-P are as follows:

 1) Smokeless, Slagless and Pollution-free
  During the modification process, there won’t occur the harmful gas and off-flavor gas, so the product is “green”-environmental friendly. The reaction slag that causes aluminum consumption will not be formed, so there is no corrosion of furnace linings, crucibles and tools, leading to that the lifetime of the linings and crucibles can be elongated. Also, the aluminum consumption can be reduced.
  2) Convenient transportation, Safe preservation and Facile addition
Similar to other aluminum alloys, there is no safety problem for the transportation and preservation of Al-P, and it can be preserved for long time and will never be inoperative. Moreover, the addition process of Al-P is very simple, so the use of Al-P can improve the productivity.
  3) Low modification temperature required, stable and long-term effective
Because Al-P master alloy has pre-generated AlP paticles, it has excellent modification efficiency for Al-Si alloys. Meanwhile, the modification temperature required is low and the modification efficiency can last for more than 30h.
  4) The absorption efficiency of P is high (up to 70%) and stable, so the addition level of P can be controlled in batching.
  5) Lower use-cost
  Combined the merits 1), 2) and 3), the use-cost of Al-P master alloy is much lower than the current modifiers.

untreated
after addition of Al-P master alloy

The microstructures of Al-12.6Si alloy before and after modification

untreated
after addition of Al-P master alloy

The microstructures of Al-24Si alloy before and after modification

untreated
after addition of Al-P master alloy

The microstructures of Al-50Si alloy before and after modification

4. Specifications

Shape: tablets and rods  Colors: silver gray  

Al-P master alloy tablets(250 or 500g per ingot)
Al-P master alloy wire(Ф9.5mm)

Table.1 The specifications, compositions and usages of series of Al-P master alloys

Binary Al-P Master Alloys

Specification

P

Others total

Usage

AlP3

2.7-3.3

≦ 0.5

Phosphorus addition and Modification treatment for alloys

AlP5

4.6-5.4

≦ 1.0

Ternary Al-Si-P Master Alloys

Specification

P

Si

Others total

Usage

AlSiP3.5

3.2-3.8

3.0-16.0

0.6

Modification treatment for eutectic and hypereutectic Al-Si alloys

AlSiP5

4.6-5.4

1.0

Ternary Al-Cu-P Master Alloys

Specification

P

Cu

Others total

Usage

AlCuP5

4.6-5.4

2.0-11.0

≦ 1.0

Modification treatment for Al-Si alloys bearing Cu

Ternary Al-Fe-P Master Alloys

Specification
P
Fe
others total
Usage
AlFeP5
4.6-5.4
2.0-11.0
≦ 0.5
Strengthening and Modification treatment for Al-Si alloys
Ternary Al-Zr-P Master Alloys

Specification

P

Zr

Others total

Usage

AlZrP5

4.6-5.4

2.0-6.0

≦ 1.0

Strengthening and Modification treatment for Al-Si alloy

 

5. Technical Supports

 Lots of investigation and development focusing on the Al-P master alloy and its modification technology have been done by the researchers in our company, and four national invention patents have been authorized. Furthermore, a series of academic articles related to Al-P master alloy have also been published, which provides the technical support to the application of Al-P master alloy.
  The published articles are mainly as follows:

  1. Guoju Bao, Min Zuo, Dakui Li, Yunguo Li, Xiangfa Liu. The improvement of microstructures and mechanical properties of near eutectic Al-Si multicomponent alloy by an Al-8Zr-2P master alloy?, Materials Science and Engineering: A,
  2. Dakui Li, Min Zuo, Qian Zhang, Xiangfa Liu. The investigation of continuous nucleation and refinement of primary Si in Al–30Si mushy zone, Original Research Article, Journal of Alloys and Compounds, Volume 502, Issue 2, 23 July 2010, Pages 304-309, (full pdf)
  3. Zuo Min, Liu Xiangfa. Twin Growth Mechanism of AlP Hexagonal Platelets in an Al-Si Melt, Crystal Growth & Design, Vol. 10, No. 6, 2010, 2443-2446 (full pdf)
  4. Zuo min, Liu Xiangfa, Dai Hongshang, Liu Xiangjun. Al-Si-P master alloy and its modification and refinement performance on Al-Si alloys, Rare Metal, Vol. 28, No. 4, Aug 2009, p. 412 (full pdf)
  5. Min Zuo, XiangFa Liu, QianQian Sun, Kun Jiang. Effect of rapid solidification on the microstructure and refining performance of an Al–Si–P master alloy, Journal of Materials Processing Technology,209 (2009) 5504–5508(full pdf)
  6. Min Zuo, Xiangfa Liu, Qianqian Sun. Effects of processing parameters on the refinement of primary Si in A390 alloys with a new Al–Si–P master alloy, J Mater Sci (2009) 44:1952–1958 (full pdf)
  7. Chong Li, Xiangfa Liu, Yuying Wu. Refinement and modification performance of Al-P master alloy on primary Mg2Si in Al-Mg-Si alloys, Journal of Alloys and Compounds, 2008; 465 (1-2) : 145-150 (full pdf)
  8. Chong Li, Xiangfa Liu,Guohua Zhong. Heterogeneous nucleating role of TiB2 or AlP/TiB2 coupled compounds on primary Mg2Si in Al–Mg–Si alloys, Materials Science and Engineering A ,497 (2008) 432–437 (full pdf)
  9. Wu Yuying, Liu Xiangfa and Bian Xiufang. The study of refinement for primary silicon in Cu-50 wt.%Si alloys, Journal of Alloys and Compounds, 2007; 433 (1-2) : 175-179
  10. Lina Yu, Xiangfa Liu, Haimin Ding and Xiufang Bian. A new nucleation mechanism of Primary Si by like-peritectic coupling of AlP and TiB2 in near eutectic Al-Si alloy, Journal of Alloys and Compounds, 2007; 432: 156–162 (full pdf)
  11. Lina Yu, Xiangfa Liu, Haimin Ding and Xiufang Bian. A new nucleation mechanism of primary Si by like-peritectic coupling of AlP and Al4C3 in near eutectic Al–Si alloy, Journal of Alloys and Compounds, 2007;429 (1-2): 119-125 (full pdf)
  12. Yuying Wu, Xiangfa Liu, Jiangang Song and Xiufang Bian. A novel method to induce the precipitation of primary silicon in commercial near eutectic Al–Si alloys, Materials Science and Engineering: A, 2007; 457(1-2): 109-113
  13. Yuying Wu, Xiangfa Liu, Binggang Jiang and Xiufang Bian. Four-branched compounds coupled Si and iron-rich intermetallics in near eutectic Al–Si alloys, Journal of Alloys and Compounds, 2007; 437(1-2): 80-83
  14. Yuying Wu, Xiangfa Liu. Effect of AlP on the eutectic nucleation in Ni–38wt.%Si alloys, Materials Science and Engineering: A, 2006; 427(1-2):69-75
  15. Xiangfa Liu, Jinguo Qiao, Yuying Wu, Xiangjun Liu, Xiufang Bian. EPMA analysis of calcium-rich compounds in near eutectic Al–Si alloys, Journal of Alloys and Compounds , 2005;388(1):83-90
  16. Xiangfa Liu, Yuying Wu, Xiufang Bian The Nucleation sites of Primary Si in Al-Si Alloys after Addition of Boron and Phosphorus , Journal of Alloys and Compounds , 2005;91(1-2): 90-94
  17. Jinguo Qiao, Xiangfa Liu, Xiangjun Liu and Xiufang Bian. Relationship between microstructures and contents of Ca/P in near-eutectic Al–Si piston alloys , Materials Letters, 2005; 59 ( 14-15) :1790-1794 (full pdf)
  18. Xiangfa Liu, Jinguo Qiao, Xihua Zhang, Xiangjun Liu, Xiufang Bian. Formation of (Ca(n-x), Nax)Pm Compounds in eutectic Al-Si piston alloys and Invalidation of Phosphorus Modification Effect, Aata Metallurgica Sinica, 2004; 40(3):245-250
  19. Xiangfa Liu, Jinguo Qiao, Yuxian Liu, Shitong Li, Xiufang Bian. Modification Performance of the Al-P master alloy for eutectic and hypereutectic Al-Si alloys. ACTA Metallurgica Sinica, 2004; 40(5): 471-476
  20. Jinguo Qiao, Xiangfa Liu, Xiangjun Liu, Xiufang Bian. Influence of Calcium on Phosphorus Modifying Eutectic Al-Si Alloys. Foundry, 2004; 53:38-40
  21. Jinguo Qiao, Xiangfa Liu, Zengjian Feng, Xiao Sun, Xiufang Bian. Influence of Al-5%Ti-0.07%B Master Alloy on the Microstructure and Properties of Al-Si Piston Alloy. Foundry, 2003;52(9): 679-681
  22. Xiangfa Liu, Jinguo Qiao, Xigui Song, Xiufang Bian, Limin Zhu, Qilin Zhang. Application of Al-P Master Alloy to Al-Si Piston Alloy, 2002;(6):43-45
     

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