铝合金铸造工艺性能，通常理解为一个模具，结晶和冷却过程中的综合这些属性最突出的表现。流动性，收缩，气密性，铸造应力，吸气性。铝合金这些特点的合金成分而定，但也与铸造因素，合金加热温度，模具的复杂性，浇冒口系统，浇口形状等。

（1）流动性

流动性指的是液态合金充型能力。在对决定是否合金铸件铸造复杂大小的流动性。共晶合金在铝合金的{zj0}流动性。

影响的因素，主要成分，温度和液体合金的金属氧化物，金属化合物及其他污染物的固相粒子的存在流动性，但根本的因素外铸造浇注温度和压力（俗称浇注压头）高和低。

实际生产中的合金，已经确定的情况下，除了强化冶炼过程（精炼和除渣），还必须提高模具进程（砂型透气性，金属型模具排气及温度），和但不影响铸件质量的前提下提高浇注温度，保证合金的流动性。

（2）收缩收缩

是铸造铝合金的主要特征合金之一。一般来说，从合金凝固考虑到寒冷的浇筑至室温液体，分为三个阶段，即液态收缩和凝固收缩和固态收缩分歧。合金铸件收缩对质量具有决定性的影响，它影响到铸造腔的大小，所产生的应力，裂纹的形成和大小的变化。铸造收缩率通常分为中的线性收缩率普遍适用的实际产量计算合金收缩成体收缩和线收缩。

合金收缩大小，通常称为如收缩百分比表示。

①体收缩

机构收缩，包括收缩和凝固收缩流动性。
从液体浇注铸造合金
巩固在那里将最终凝固宏观或微观收缩，而由于受到宏观引起收缩收缩可见肉眼分为集中和分散的收缩性质划分腔。光圈收缩的重点，集中在大型和重型铸件截面分布在顶部或原子能机构热节。腔分散形态零散的小，其中大部分是在铸造轴和热部分的内容。微腔很难用肉眼看到，在晶界或晶间多数微收缩枝。

铸造收缩和骨质疏松症的主要缺点，是收缩的原因之一是大于液固收缩。生产发现，小型的铸造铝合金凝固范围，更容易形成集中缩孔，凝固范围广泛，更容易形成腔分散，因此，在设计，必须与铸造铝合金订单行了凝固原则，即，铸造过程中的液体，液体合金收缩身体凝固应该补充的萎缩，骨质疏松症是在外部风险的人口铸造集中。轻松的多孔铝合金铸件分散，冒口设置数量比收缩集中，容易感冒铁竖立松散许多，增加当地冷却速度，这样，在同一时间或快速凝固。

②线收缩

线收缩大小将直接影响铸件的质量。该线收缩越大，铝铸件有一种倾向，打击和压力更大，冷却铸造的大小和形状的更大的变化。
不同的铸造铝合金铸件
有不同的收缩率，即使同一合金，铸件不同的收缩是不同的相同，铸造，其长度，宽度和高度的收缩率也不同。应根据案件的具体情况。

（3）铝铸件热裂纹

热裂纹的主要原因是主要是沿晶界的观察可见裂纹裂缝处金属往往氧化，造成断裂比金属铸件收缩应力，晶粒之间的结合能力，损失的金属光泽。裂缝沿锯齿形晶界扩展，在广泛的内部较窄，而另一些穿透面对整个铸造表面。

不同铝合金铸件有裂纹倾向是不同的，因为这是铸造铝合金凝固过程中开始参与的温度范围内xx结晶的形状和更大的凝固之间的温差越大，合金收缩，导致更大的热裂倾向，甚至与铸造合金由于阻力，对铸件的结构，铸造技术和其他因素对热裂倾向也不同。生产的模具常用让路，或改善铸造铝合金铸件系统，如措施，以避免铝铸件开裂。通常热分裂检测环铸造铝合金热裂纹。

（4）气密性

气密性铸造铝合金体腔是指在高压气体或液体铝铸件没有渗漏下的气密性的特征，其实铸造了内部组织致密程度和纯净。

气密性铸造铝合金和合金的性质，合金凝固范围较小，导致骨质疏松往往较小，同时，有一个较小的降水毛孔，而合金气密性更高。铸铁的混合气体，紧张，但随着铸造工艺也，铝合金等铸造铝合金降低浇注温度，放置冷铁以加快冷却速度和压力下凝固，结晶等，可以使铝铸件的气密性提高。渗透也可以用来堵塞泄漏的差距气密性提高铸件。

（5）铸造铸件应力

应力包括热应力，相变应力和收缩三讲。压力产生不同的各种原因。

①热应力

热应力是由于厚薄不均的铸件接口部分不同几何形状，冷却造成的不一致。形成于薄壁压应力，在铸件残余应力的产生。

②相变应力相变应力

是由于一些凝固过程铸造铝合金冷却后的相变，带来的音量大小的变化。主要壁厚不均匀铝铸件在不同地区内的相变，由于不同的时间发生。

③收缩应力

铝铸件的模芯产生拉应力，由于收缩障碍。这压力是暂时的，铝铸件开箱即会自动消失。不过，开箱时间不当，往往会导致热裂，尤其是金属铝合金铸造，是在压力下往往容易出现这样的热裂纹。

铸铝的残余应力降低合金配件合金的力学性能，加工的精密铸件的影响。残余应力铝铸件通过退火处理xx。由于合金导热性好，冷却过程中无相变，只要有合理的结构设计铸造，铝铸件残余应力一般较小。

（6）吸气

合金易吸收气体，是铸造铝合金的主要特点。液态铝和铝合金收费的组成部分，有机物质和水分含量的模具燃烧产品等，从吸氢反应造成的原因是铝液。

越高铝合金熔体温度，氢吸收也比较;在700每100克氢溶解度铝℃为0.5?0.9，温度为850℃，氢溶解度增加2?3倍。当碱金属杂质，在液态氢铝溶解度显着增加。除了铸造铝合金

吸气融化时，在进入模具浇注也必须吸进与液态金属的温度下降模具，气体溶解度降水减少多余气体，有逸不是气体的一部分留在铸件形成气孔，这通常是所谓的“针孔”。燃气有时结合腔，铝液沉淀在气体继续留在腔。如果是泡沫的压力产生的热量，而气孔，表面光滑，有一个洞，周围的圆圈光明层;如果小气泡的压力下，表面的孔许多皱纹，看起来像“苍蝇脚”，而且还仔细观察收缩特征。

铸造铝合金越高，液态氢量，生产铸件针孔你。中等铸造铝铸件针孔不仅降低了气密性，耐蚀性，也降低了合金的力学性能。为了获得非气孔孔或铝铸件少，关键是要融化的条件。如果溶剂时，将覆盖面，以保护合金吸气量大为减少。论精炼铝液的处理，可以有效地铝在液态氢量控制。

Aluminum Alloy Casting Process Performance

Aluminum alloy casting process performance, is usually understood as in a mold, the process of crystallization and cooling performance of the most prominent of those properties of the Composite. Mobility, shrinkage, air tightness, casting stress, inspiratory sexual. Aluminum alloy these characteristics depend on the alloy composition, but also with the casting factors, alloy heating temperature, the complexity of the mold, pouring riser systems, gate shape and so on.

(1) mobility

mobility refers to the liquid alloy mold filling capacity. The mobility of the size of the decision whether alloy castings foundry complex. Eutectic alloy in the aluminum alloy the mobility of the best.

affect the mobility of a number of factors, primarily components, temperature and liquid alloy the existence of metal oxides, metal compounds and other pollutants in the solid-phase particles, but the fundamental factors external pouring temperature and casting pressure (commonly known as pouring pressure head) of the high and low.

actual production, in the alloy have been identified circumstances, apart from strengthening the smelting process (refining and deslagging), it is also necessary to improve the process of mold (sand mold permeability, metal-type mold venting and temperature ), and without prejudice to the premise of casting quality improve pouring temperature, and ensure the mobility of the alloy.

(2) systolic contractility

are cast aluminum alloy one of the major characteristics. Generally speaking, the alloy solidified from the liquid pouring into account until the cold to room temperature, is divided into three phases, namely liquid contraction and solidification shrinkage and solid-state contraction. Shrinkage of alloy castings have a decisive impact on the quality, it affects the casting cavity size, the resulting stress, crack formation and size changes. Casting shrinkage usually is divided into body contraction and linear contraction in the actual production in the general application of linear shrinkage measured alloy contractility.

alloy contraction size, usually expressed as a percentage, known as shrinkage.

① body contraction

body contraction, including contraction and solidification shrinkage liquid.

from pouring liquid casting alloys to solidify in the final solidification of the place there will be macro-or micro-contraction, which due to shrinkage caused by macro-shrinkage visible to the naked eye and is divided into centralized and decentralized nature of shrinkage cavity . Shrinkage of the aperture to focus and concentrate on large and distributed in Heavy cross section castings at the top or the hot section of the Agency. Cavity dispersion morphology of the fragmented small, most of which lies in the casting axis and the hot section parts. Micro-cavity is difficult to see the naked eye, micro-shrinkage in the majority of grain boundaries or dendrite of the inter-dendrite.

casting shrinkage and osteoporosis are major shortcomings, one of the causes of contraction are greater than the liquid-solid contraction. Production found that the smaller the range of cast aluminum alloy solidification, the more easy to form concentrated Shrinkage, solidification wide scope, the more easy to form cavity dispersion, therefore, in the design must be made in line with the order of cast aluminum alloy solidification principles, namely, casting in liquid to the solidification of the body during the contraction of the liquid alloy should be added that shrinkage and osteoporosis are concentrated in the casting of external risk population. Easily dispersed on the porous aluminum alloy castings, riser set quantity to many than the concentration of shrinkage and easy to erect loose cold iron, increasing local cooling rate, so that at the same time or rapid solidification.

② linear shrinkage

linear shrinkage size will directly affect the quality of castings. The greater the linear shrinkage, aluminum castings have a tendency to crack and stress greater; cooled casting size and shape of the bigger changes.

for different casting aluminum alloy casting has a different shrinkage rate, even if the same alloy, casting different shrinkage is different, in the same casting, its length, width and height of the contraction rate are also different. Should be based on the specific circumstances of the case.

(3) hot cracking of aluminum castings

hot cracks was mainly due to the casting shrinkage stress than the metal-binding capacity between grains, mostly along the grain boundary fracture resulting from crack observation visible cracks Department metals are often oxidation, the loss of metallic luster. Cracks along the grain boundary extension of the zigzag shape, the surface of a wide internal narrower, while others penetrate the entire cast of the face.

different aluminum alloy castings have a tendency to crack is different, because this is the cast aluminum alloy solidification process began to take shape in the complete crystallization of the framework of the temperature and the greater the difference between the solidification temperature, the greater the alloy shrinkage, resulting in the greater the tendency to hot crack, even with a cast alloy due to the resistance, the structure of castings, casting technology and other factors have a tendency to hot cracking are also different. Production of the mold is often used to give way, or to improve the casting aluminum alloy casting systems, such as measures to avoid cracking of aluminum castings. Usually detected by hot split ring casting aluminum hot crack.

(4) gastightness

gastightness cast aluminum alloy body cavity refers to aluminum castings in high pressure gases or liquids do not leak under the degree of air tightness in fact characterized Casting the internal organization of the extent of dense and pure.

gastightness cast aluminum alloy and the nature of alloys, alloy solidification range of the smaller, resulting in osteoporosis tend to have smaller, at the same time have a precipitation of the smaller pores, while alloy gastightness higher. Cast aluminum alloy with a mixed gas-tight, but also with the casting process, such as cast aluminum alloy lower pouring temperature, place the cold iron to accelerate the cooling rate and solidification under pressure, crystallization, etc., can make aluminum castings gastightness提高. Infiltration can also be used to plug the leak gap gastightness improve casting.

(5) foundry casting stress

stress including thermal stress, phase-change stress and contraction stress of three. Stress generated by a variety of different reasons.

① thermal stress

thermal stress is due to different geometry of the casting interface section of uneven thickness, cooling caused inconsistencies. Formed in the thin-wall compressive stress, resulting in residual stresses in the castings.

② phase transition phase transition stress

stress was due to some cast aluminum alloy in the solidification process after the cooling phase change, brought changes in the volume size. Main wall thickness aluminum castings are uneven in different parts at different times within the phase change due to happen.

③ shrinkage stress

aluminum castings contraction by the mold core obstacles arising due to tensile stress. This stress is temporary, and aluminum castings are out of the box will automatically disappear. However, the time out of the box properly, often lead to hot cracking, especially in metal casting of aluminum alloy are often under stress in such a prone hot crack.

cast aluminum alloy parts of the residual stress reduces the mechanical properties of alloys, the impact of the machining precision castings. Aluminum castings of residual stress through the elimination of the annealing treatment. Alloy because of good thermal conductivity, cooling process without phase change, as long as the structural design of a reasonable casting, aluminum castings generally smaller residual stress.

(6) of inspiratory

alloy easy to absorb gases, are the main characteristics of cast aluminum alloy. Liquid aluminum and aluminum alloy components with the charge, the products of combustion of organic matter and moisture content of the mold, etc. resulting from the reaction of hydrogen absorption was caused by liquid aluminum.

The higher the temperature of molten aluminum alloy, the hydrogen absorption is also more; at 700 ℃ for every 100g of hydrogen solubility in aluminum is 0.5 ~ 0.9, temperature to 850 ℃, the hydrogen solubility increases 2 ~ 3 times. When the alkali metal impurities, the hydrogen in liquid aluminum solubility increased significantly. In addition to cast aluminum alloy

inspiratory melting when, in pouring into the mold will also have to inhale into the mold with liquid metal as the temperature dropped, the gas solubility decreased precipitation excess gas, has Yat not part of the gas remain in the casting to form pores, which is usually called the “pinhole.” Gas is sometimes combined with the cavity, aluminum liquid precipitation to remain in the gas inside the cavity. If the heat generated by the bubble pressure, while stomatal smooth surface, has a circle around the hole bright layer; if the pressure of small bubbles, the surface hole many wrinkles, looks like “a fly foot”, but also has carefully observed shrinkage characteristics.

-cast aluminum alloy the higher the volume of liquid hydrogen, produced castings pinhole you have. Medium pinhole aluminum castings castings not only reduce the air tightness, corrosion resistance, also reduces the mechanical properties of alloys. To obtain non-stomatal pores or less of aluminum castings, the key lies in the conditions of melting. If the melting agent, when added coverage to protect the alloy inspiratory volume greatly reduced. On for refining molten aluminum processing, aluminum can be effectively contained in the volume of liquid hydrogen. (07-12-7)