钛合金 - 物理性质

主题涵盖

背景

密度

力量

导热系数

电阻率

磁性特性

松紧带模量

泊松比

Tensile Strength

硬度

蠕动

疲劳

断裂韧性。

背景

The physical properties of titanium and its alloys are summarised in Table 1, from which it can be seen that there is little variation from one alloy to another. For example, coefficients of thermal expansion range from 7.6x10^-6K^-1到9.8x10.^-6K^-1.

表格1。Physical properties of titanium and titanium alloys.

Table 1 (cont.).Physical properties of titanium and titanium alloys.

密度

The density of an alloy is dependent upon the amount and density of the alloying constituents. For example, an alloy containing aluminium as an alloying element is likely to be substantially lighter than one containing an appreciable amount of tin. Generally, beta alloys are heavy because they contain alloying constituents such as molybdenum which has a relatively high density. Where weight is important, it may be worthwhile to compare specific properties of alloys, e.g. the specific strength.

力量

在表2中，将一些钛合金的比强度与其他结构金属的比较。

表2。力量of some titanium alloys at room temperature, normalised通过密度，与其他结构金属相比。

导热系数

所有钛合金的导热系数对于金属相对较低，但最近的工作表明，商业上纯钛的价值实际上是21.6 W m^-1.k.^-1，比表1中引用的值高约32％。钛合金通常具有比商业上纯材料更低的导热性。

电阻率

从此可能预期，电阻率相对较高。特定的热量没有显示出任何明显的趋势，范围从约400到600 j.kg^-1.k.^-1.

磁性特性

商业纯钛和所有钛合金是非磁性的。商业纯钛的渗透率为1.00005-1.0001，955小时^-1.

松紧带模量

Values of elastic (Young's) modulus typically range from 80 to 125 GPa, but this depends to some extent on the working process used to produce the material and on the directionality of the test material. There is, however, a general tendency for high aluminium containing materials to have a somewhat higher modulus than other alloys.

泊松比

It is difficult to give a reliable value for Poisson's ratio for titanium alloys since anisotropy leads to small differences in both elastic and shear moduli which, when taken together to calculate Poisson's ratio can lead to values varying from 0.287 to 0.391 for annealed ASTM Grade 5 (Ti-6%Al-4%V) sheet. However, the generally accepted value for commercially pure titanium is 0.36 and that for ASTM Grade 5 is 0.31.

温度对物理性质的影响

在表3中给出了温度对商业上纯钛物理性质的影响。该合金遵循类似的图案，尽管导热率趋于在升高的温度下升高，但大多数合金显示环境和环境之间的增加60％至80％500°C。其他性质更加遵循商业纯钛的趋势。

表3。Effect of temperature on the physical properties of comeercially pure titanium.

Tensile Strength

在环境温度下钛及其合金的拉伸强度范围为240MPa，用于最柔软的商业纯钛的级别为1400mPa，用于非常高的强度合金。根据成绩和条件，证明优势在约170至1100MPa范围内变化。详细信息在表4中给出。

表4。保证钛合金的性能。

A =处理，B =典型值

在升高的温度下，每个等级的钛表现出特征拉伸性能。合金等级，特别是高强度材料，将证明和拉伸强度保持高于商业纯度的高温。欧洲杯足球竞彩这在图1和2中清楚地示出。延展性通常随温度的增加而增加，如图3所示。然而，在商业上纯的等级中存在轻微的不规则性，因为延展性始终增加到200°C和温度之间的延伸增加如下300℃，但后，直至400至450°C值与室温下的值非常相似。

硬度

The absorption of oxygen into a titanium surface when the material is heated causes an increase in hardness of the surface layer. Grinding and polishing can have a similar effect on metallurgical samples and it is for this reason that hardness values can be misleading. However, the hardness of titanium, if interpreted correctly, can be a useful measurement for the following purposes:

•硬度can be used to give a rough indication of the identity of a grade of titanium alloy;

•Comparison of hardness before退火后可用于估计最初存在的工作程度或根据具体情况来退火的完整性;

•对于某些合金，已知硬度和拉伸强度之间的关系。因此，可以使用硬度测量来赋予局部机械性能的指示，例如失效的部件的片段，或者可选地检查热处理的成功。

图4说明了商业纯钛的硬度与其拉伸强度之间的近似关系。

蠕动

有关商业纯钛的蠕变性质的公开信息很少，主要是因为目前的应用程序通常不需要对此属性的详细了解。通常，在100,000小时内将材料的蠕变值为0.1％塑性菌株，在高达300℃的温度下的拉伸强度的约50％。

化工厂的设计码允许使用高达150°C的设备的拉伸信息，这涵盖了化学工业中商业纯钛的大部分目前使用。2020欧洲杯下注官网在上述温度下，钛通常用作钢支撑的衬里。化学厂设计码还指压力破裂值和信息中的信息在图5和6中给出。

显然，一些应用需要使用具有良好抗蠕变和钛合金的材料，并且多年来已经开发出了达到这一要求。他们通常分为三大类：

•α-beta合金。这些含有足够的β稳定元素，以允许一些β相在室温下保留。它们在α-β相域中进行热处理，其结构由初级α和转化的β组成。这些材料的蠕变条件下的最大工作温度通常为300-450°C;欧洲杯足球竞彩

•Near alpha alloys heat treated in the alpha-beta phase field. By optimising alpha and beta stabilising elements, alloys have been developed which have improved creep resistance at temperatures in the range 450-500°C;

•近α合金在β相田中进行热处理。通过在β相域内的α合金附近的热处理获得蠕变性质的显着进一步改善，并且这种材料适用于高达600℃。欧洲杯足球竞彩

疲劳

与它们的拉伸强度相比，钛合金的高循环疲劳强度通常良好。虽然S-N疲劳曲线不会像金属一样显示出锋利的膝盖，但它们往往会在大约10左右变平⁷cycles and the fatigue limit thus defined is between 40 and 60% of the tensile strength. The effect of notches is less than could be expected from the stress concentration factors and fatigue crack propagation rates, and residual static strengths of cracked samples compare favourably with those of steels and aluminium alloys. Comparison of specific fatigue strengths of titanium alloys with other high strength materials is included in Table 2.

与其他材料一样，钛的疲劳性能欧洲杯足球竞彩随表面饰面而变化，缺口标本试验基本上比具有不存在的样品的值基本较低的值。因此，设计和制造中需要护理以避免应力集中器。表面光洁度差，尖锐的截面过渡，未混浊的半径和角落是应避免的条件。

钛合金的低循环疲劳性能与飞机应用中的旋转部件有关。大多数数据已经在恒定负载下产生，零最小应力条件，其中建立了合金的疲劳强度与强度和延展性密切相关。

断裂韧性。

钛合金的韧性取决于强度，组成，微观结构和质地，性质是相互关联的。然而，一般而言，钛合金的韧性以与钢或铝合金的方式相同的方式与强度相同。例如，α-β合金的普通菌株断裂韧性从60到100mPam的值下降^-½.在800MPa的证明应力水平，到20至60 MPa.m^-½.在证明1200 MPa的压力水平。一般来说,届e heat treatments that are normally used with titanium were originally developed to give optimum tensile properties rather than to improve fracture toughness. However, it has been established that for certain alpha-beta alloys it is possible to increase fracture toughness significantly by simple changes in heat treatment procedure or by a minor variation in alloy chemistry, for example, by reducing the oxygen level in the Ti-6%Al-4%V alloy to produce the extra low interstitial (ELI) grade. Such improvements are generally only associated with small decreases in tensile and fatigue strengths. Other alloy types such as the beta heat treated near alpha alloys have better fracture toughness levels than the alpha-beta types.

资料来源：材料信欧洲杯足球竞彩息服务 - 选择和使用钛，设计指南

有关此来源的更多信息，请访问The Institute of Materials.