Master Alloys for Aluminum Alloys: Part Two

요약:

The article summarizes common additions are used for aluminum alloys, the engineering practice has acquired the following main addition methods for them, and recommendations, which should be kept in mind for selection of the master alloys and performing the aluminum alloy modification and grain refinement.

The following common additions are used for aluminum alloys, and the engineering practice has acquired the following main addition methods for them:

  • Boron is added to precipitate transition metal impurities such as Ti and V and so improve electrical properties. It is mainly added as a dilute master alloy <1% B). Originally borax (Na2B4O7), or B2O3 was added to the electrolytic cell, or KBF4 was added to the melting furnace to tie up transition metal impurities such as vanadium and titanium which adversely affect electrical conductivity of aluminum. These procedures resulted in cell contamination, or generation of toxic fumes and residual spent salt (KAlF4) in the melting furnace.
  • Bismuth is added both as the pure metal and as a dilute master alloy to enhance machinability of the aluminum alloys.
  • Chromium prevents grain growth in Al-Mg alloys, inhibits recrystallization in Al-Mg-Si and Al-Mg-Zn alloys, and corrects for Fe to produce a golden color in anodizing. The main addition form is the concentrated tablet or briquette, although a significant quantity is also added as dilute master alloy.
  • Copper is added mainly to increase strength, and it is added in many forms (pure metal, master alloys, concentrated tablets, and powder injection).
  • Iron improves the high-temperature strength of some kinds of alloys. Addition forms are similar to that for copper.
  • Magnesium provides high strength with good ductility, together with excellent corrosion resistance and weldability. For AI-Si alloys, it also improves heat treatment ability. It is mostly added as the pure metal, although master alloys are also widely used.
  • Manganese improves strength and also plays a role in preventing recrystallization. The main technique of addition is as concentrated tablets or briquettes, powder injection, and, to a lesser extent, master alloys.
  • Lead, like bismuth, is principally used to enhance machinability. The main method of addition is as the pure metal, although concentrated tablets and master alloys are also used.
  • Silicon is used in "foundry alloys" (silumines) as it gives excellent fluidity in casting. It is also used in extrusion alloys, to which it contributes high mechanical properties. The main method of addition is as pure metal, but significant amounts are added as master alloys and through powder injection.
  • Strontium is added to modify the eutectic in Al-Si alloys. It is mostly added as a dilute master alloy.
  • Titanium provides an important contribution to grain refinement. It is mainly added as tablets (including pure metal), but most often through master alloys.
  • Zinc is used to improve strength. It is almost exclusively added as the pure metal.
  • Zirconium is added to inhibit recrystallization. It is mainly added as a master alloy (up to 15% Zr), but also as a concentrated tablet.

Tabele 1. Aluminium Master Alloys.

The contents are summarized in the following statements or recommendations, which should be kept in mind for selection of the master alloys and performing the aluminum alloy modification and grain refinement. A good guideline rule tells us that there are no absolute guidelines, but all possible factors should be taken into account:

  • Aluminum alloy history (processing, impurities, possible metallurgical heritage, charge composition, i.e. scrap content, etc.).
  • Casting technology parameters (heating rate, overheating temperature, soaking time, pouring temperature, and soaking time at this point, crystallization rate at different parts of castings, etc.).
  • The results of the microstructural, macrostructural, and physical investigation, that is are the alloy processing parameters optimal from the point of view of grain size, mechanical properties, foundry defects, etc. If not, can temperature and time programs be adjusted, and what will the result be in that case.
  • When the optimal processing parameters are fixed, the selection of modifying master alloy(s) may be done on the basis of the most desired effect (grain size refinement, DAS decrease, strength and elongation increase, hardness adjustment, etc.)
  • The optimal amount of master alloy(s), introduction temperature and time, soaking, mixing, and pouring parameters have to be determined on the basis of target properties of castings. The formation of possible metastable phases and their influence on the morphology and microstructure of the final alloys should be taken into account. This requires more scientific effort to be applied to the problem before the operational window is set up for the casting process.

기술 자료 검색

검색할 어구를 입력하십시오:

검색 범위

본문
키워드

머릿글
요약

이 문서는 전체 문서 중 일부분입니다. 이 주제에 대해 더 읽고 싶으시면 아래 링크를 클릭하시면 됩니다.

Total Materia는 다양한 나라와 규격에 따른 수천개의 알루미늄 재질에 대한 정보를 포함하고 있습니다.

재질의 화학적 조성, 기계적 특성, 물리적 특성, 고급 물성 데이터 등의 전체적인 특성 정보들을 어디서든 검토하실 수 있습니다.

고급 검색을 이용하여, 검색 조건의 재질 리스트에서 '알루미늄'을 선택합니다. 검색 범위 좀 더 줄이기를 원하신다면 국가/규격과 같은 다른 조건을 지정할 수 있습니다.

검색 버튼을 클릭합니다.


선택된 정보에 부합하는 일련의 재질이 검색됩니다.


결과 리스트에서 재질을 선택하시면, 일련의 규격 사양 소그룹이 나타납니다.

여기에서 선택한 재질의 특정 특성 데이터를 검토하실 수도 있고, 강력한 상호 참조 표를 이용하여 유사 재질이나 등가 재질을 검토하는 것 또한 가능합니다.


자세한 특성 데이터를 보시려면 특성 데이터 링크를 클릭하세요.




Total Materia 데이터베이스를 사용해 보실 수 있는 기회가 있습니다. 저희는 Total Materia 무료 체험을 통해 150,000명 이상의 사용자가 이용하고 있는 커뮤니티로 귀하를 초대합니다.