Fracture Toughness Of Aluminum Alloys Research Articles

Fracture toughness of aluminum alloys in air and 115 MPa hydrogen gas and strength design of thick-walled cylinder

Fracture toughness of aluminum alloys in air and 115 MPa hydrogen gas and strength design of thick-walled cylinder

An indentation technique for estimating the energy density as fracture toughness with Berkovich indenter for ductile bulk materials

A technique is proposed to estimate the energy density as fracture toughness for ductile bulk materials with an indentation system equipped with a Berkovich indenter based on the theory of plastic deformation energy transforming into the indentation energy of fracture. With progressive increase of penetration loads, the material damage is exhibited on the effective elastic modulus. A quadratic polynomial relationship between the plastic penetration depth and penetration load, and an approximate linear relationship between logarithmic plastic penetration depth and logarithmic effective elastic modulus are exhibited by indentation investigation with Berkovich indenter. The parameter of damage variable is proposed to determine the critical effective elastic modulus at the fracture point. And the strain energy density factor is calculated according to the equations of penetration load, plastic penetration depth and effective elastic modulus. The fracture toughness of aluminum alloy and stainless steel are evaluated by both indentation tests and K IC fracture toughness tests. The predicted S cr values of indentation tests are in good agreement with experimental results of CT tests.

Effects of pre-stretching and ageing on the strength and fracture toughness of aluminum alloy 7050

The effects of the pre-stretching and ageing on the microstructure, strength and fracture toughness of the 7050 aluminum alloy were investigated by means of optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile test and the plane-strain fracture toughness test. The results indicate that the peak aged 7050 aluminum alloy possesses a higher strength, but its fracture toughness is poor. The high temperature and a subsequent low temperature ageing improve the fracture toughness by 8% while the strength is decreased by 3.5%. The fracture toughness of the over aged 7050 aluminum alloy is enhanced by 29% with a decrease in the strength of 7%. The retrogression and reaging provides an optimum combination of the strength and fracture toughness, which improves the fracture toughness by 17% without sacrificing the strength. After the pre-stretching, the precipitates within grains become coarse for all the ageing tempers which results in a lower strength. While the strength difference between the matrix and the grain boundary become lower and the area fraction of the grain boundary precipitates become smaller, leading to the higher fracture toughness.

Effect of solution treatment on the strength and fracture toughness of aluminum alloy 7050

The effect of the solution treatment on the tensile property and fracture toughness of aluminum alloy 7050 were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test and the plane-strain fracture toughness test. The results show that with increasing single-stage solution temperature, the volume fraction of the residual phase decreases, but the volume fraction of the recrystallized grains and the size of the sub-grains increase. Thus, the strength and fracture toughness of the single-stage solution treated samples increase first and then decrease. The enhanced solution treated samples result in an improved dissolution of the residual phase, a lower recrystallized grains fraction and smaller sub-grains, which leads to a higher strength and fracture toughness than that of the single-stage solution treated samples. The grain structure of the high temperature pre-precipitation treated samples is similar to that of the enhanced solution treated samples. However, the high temperature pre-precipitation treated samples exhibit a lower strength and fracture toughness, due to a mass of AlZnMgCu phase precipitating from the matrix.

The influences of multiscale-sized second-phase particles on ductility of aged aluminum alloys

Commercially aged aluminum alloys commonly contain second-phase particles of three class sizes, and all contribute appreciably to the mechanical properties observed at the macroscopic scale. In this article, a multiscale model was constructed to describe the individual and coupling influences of the three types of second-phase particles on tensile ductility. The nonlinear relationships between the parameters of particles, including volume fraction, size, aspect ratio, shape, and ductility, were then quantitatively established and experimentally validated by the measured results from disc-shaped precipitate containing Al-Cu-Mg alloys and needle-shaped precipitate containing Al-Mg-Si alloys, as well as by using other researchers’ previously published results. In addition, we discuss extending this model to predict the fracture toughness of aluminum alloys.

239 Numerical approach on dynamic fracture toughness of aluminum alloy under short pulse impact loading

An impact of one-point bend test apparatus is developed for conducting test at high rates of stress up to 10^7 MPa. m^<1/2>.s^<-l/2>. The aluminum alloy 7075-T651 tested in one-point bend show increasing degree of rate sensitivity above 10^5 MPa. m^<1/2>.s^<-1> to 10^6 MPa. m^<1/2>.s^<-l/2>. On the other hand, the compression tests in the literature show essentially no strain rate sensitivity. A numerical analysis is conducted to investigate the stress-state ahead of the crack tip.

Effect of Microstructure on Mechanical Properties and Fracture Toughness of Aluminum Alloy Die Castings.

The effect of microstructure, especially DAS II (Secondary Dendrite Arm Spacing) and chill layer in ADC10 aluminum alloy die castings on the tensile properties, the fracture toughness and the crack propergation is examined by preparing the die castings which have different DAS II and different thickness of chill layer cast under several casting conditions by cold chamber die casting machine. The results are as follows. (1) The tensile strength increases with the decrease in DAS II and there is the Hall-Petch relation between DAS II and 0.2% proof stress. While DAS II doesn't affect the fracture strain. (2) As a crack propagates through the boundary between α-phase and eutectic Si crystal, the increase in DAS II makes the fracture surface be rougher and it causes the increase in the fracture toughness. (3) The tensile strength and the surface hardness of chill layer are higher than substrate. It is possible for the reason to be not only relaxation of stress concentration due to small DAS II but also strengthening by solid solution due to the larger amount of occluded copper and magnesium.

Fracture toughness of aluminum alloys of the system Al-Mg-Si for cyclic and static loads

Fracture toughness of aluminum alloys of the system Al-Mg-Si for cyclic and static loads

Effect of Hydrostatic Pressure on Fracture Toughness of Aluminum Alloys

材料のき裂に対する抵抗力(破壊じん性)の静水圧による変化を調べるために, 二種のアルミニウム合金についてASTM規格に基づいた破壊じん性試験を4 200気圧までの静水圧下で行った.破壊じん性は静水圧とともに増加する.そのため, 低圧下で不安定な破壊をする材料であっても, 十分静水圧が高くなると安定な破壊に移行する.限界き裂先端開口変位を用いた非線形力学の手法により, 破壊じん性の静水圧による増加現象を考察した.

Influence of the quantity and form of intermetallic inclusions on the fracture toughness of aluminum alloys

Influence of the quantity and form of intermetallic inclusions on the fracture toughness of aluminum alloys

Fracture toughness of cryogenic alloys and determination of their structural strength

1. For steels of the transition (07Kh16N6) and martensitic classes (03Kh12N10MT) the fracture toughness is fairly high under plane strain conditions down to 4.2°K. 2. The fracture toughness of aluminum alloys 1201 and 01381 increases with decreasing temperatures down to 4.2°K, although the presence of defects in weld seams cuts the structural strength in half. 3. The fracture toughness of titanium alloy VT5-1kt is approximately the same as that of the steels at 4.2°K. The value of KIc decreases in liquid hydrogen, which is due to the interaction of the metal with gaseous hydrogen.

Metallurgical factors affecting fracture toughness of aluminum alloys

Crack extension in commercial aluminum alloys proceeds by the “ductile” or fibrous mode. The process involves the large, ~1 μm to ~10μm, Fe-, Si-, and Cu-bearing inclusions which break easily, and the growth of voids at the cracked particles. The linking-up of the voids is accomplished by the rupture of the intervening ligaments, and this is affected by the fine, ~0.01μm precipitate particles that strengthen the matrix. The ~0.1μm Cr-, Mn-, and Zr-rich intermediate particles are more resistant to cracking and may enter the process in the linking-up stage. The fracture toughness of aluminum alloys therefore depends on a) the extent of the heavily strained region ahead of the crack tip, which is a function of the yield strength arad modulus, b) the size of the ligaments which is related tof c, the volume fraction of cracked particles, and c) the work of rupturing the ligaments. An approximate analysis predicts KIc varies asf c-1/6, and this is in agreement with measurements on alloys with comparable yield strength levels. Studies in which the aging conditions are altered for the samef cshow that the toughness decreases with increasing yield strength level. This degradation in toughness is related to the localization of plastic deformation. The tendency for localization is illustrated with the help of “plane strain” tension and bend specimens whose behavior is related to the toughness. Measurements of the strain distribution on the microscale show that slip is relatively uniformly distributed in a 7000-type alloy with low inclusion and particle content when the material is in the as-quenched and overaged conditions. In contrast the distribution is highly nonuniform in the peak aged condition where slip is concentrated in widely spaced superbands involving coarse slip bands with large offsets that crack prematurely. The connection between the tendency for slip localization and the fine precipitate particles which strengthen the matrix remains to be established. In overaged alloys grain boundary ruptures occur within the superbands. The amount of intergranular failure increases with grain size and is accompanied by a loss of fracture toughness.

Discussion of “metallurgical factors affecting fracture toughness of aluminum alloys”

Discussion of “metallurgical factors affecting fracture toughness of aluminum alloys”

Experimental study of the variation in the fracture toughness of aluminum alloys

Experimental study of the variation in the fracture toughness of aluminum alloys