Effect of Heat Treatment on Fracture during Bending in AA6016 Aluminium Alloy Sheets

2011 ◽  
Vol 488-489 ◽  
pp. 521-524
Author(s):  
Aleksandar Davidkov ◽  
Roumen H. Petrov ◽  
Peter De Smet ◽  
Leo Kestens
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Volume Fraction ◽  
Boundary Structure ◽  
Homogeneous Distribution ◽  
Fracture Mechanisms ◽  
Al Alloy ◽  
Technological Parameters ◽  
The Matrix ◽  
Strengthening Phases

The bending properties of high strength precipitation-hardening AA6016-type Al alloy thin sheets in pre-aged T4P temper state were studied in this work. Microstructural features like grain boundary particles distribution and volume fraction of the matrix strengthening phases were considered as factors controlling the mechanical properties and the fracture of this grade. Remarkable decrease in ductility, accompanied by severe deterioration of bendability occurred when coarse precipitates were found into the grain boundaries. The in-situ fracture sequence investigations as well as the post-failure surfaces observations indicated that grain boundary ductile fracture mechanisms were involved in the propagation of the cracks during bending. Heat treatment simulations were carried out and the results showed that the precise control of the technological parameters during production of these sheets is the key factor responsible for obtaining an appropriate combination of strength and bendability. Only by providing both, homogeneous distribution of the matrix strengthening phases and a favourable grain boundary structure, the severe and often contradictory requirements for the functional properties of these alloys can be successfully satisfied.

Effect of Addition of Al & Ca and Heat Treatment on the Cast Mg-6Zn Alloy

2013 ◽  
Vol 765 ◽  
pp. 33-37 ◽  
Author(s):  
S.S. Joshi ◽  
M.S. Mohan ◽  
S. Seshan ◽  
S. Kumar ◽  
S. Suwas
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Tensile Properties ◽  
Volume Fraction ◽  
Corrosion Behaviour ◽  
Boundary Phase ◽  
Al Content ◽  
Β Phase ◽  
The Matrix

In the present investigation, the effect of addition of Al and small amounts of Ca as well as the effect of heat treatment has been investigated on microstructure, tensile properties and corrosion behaviour of Mg-6Zn alloy produced by squeeze casting. The Mg-6Zn-1Al (ZA61) alloy consisted of α-Mg grains and MgZn (β) phase at the grain boundaries with a much higher strength and ductility than pure Mg. The addition of 0.1 and 0.5 wt% Ca to the ZA61 alloy refined the grain size and increased the volume fraction of the grain boundary phase but did not change the nature of the phase. Consequently, strength increased without much reduction in ductility. The increase in Al content of the alloy to 4 wt% (ZA64) changed the grain boundary phase to Al5Mg11Zn4 (Φ) phase, increased its volume fraction and refined the grain size as compared to ZA61 alloy. Consequently, strength increased with a reduction in ductility. On heat treatment of ZA61+0.5Ca and ZA64 alloys, the volume fraction of grain boundary phases decreased, fine precipitates were obtained in the matrix and the grain size increased. Thus, higher strength with a lower ductility was obtained on heat treatment but the ductility of both the alloys was still higher than that of pure Mg. Thus, 130 MPa 0.2%PS, 225 MPa UTS and 4.9% elongation to fracture could be obtained for the squeeze cast ZA64 alloy in the T6 condition, which are very good tensile properties for a cast Mg alloy. Increase in Al content and heat treatment reduced the corrosion resistance and addition of Ca improved it. The highest corrosion rate was observed to be 0.85 mm/year for the ZA64 alloy in the T6 condition.

scholarly journals Influence of matrix characteristics on fracture toughness of high volume fraction Al2O3/Al–AlN composites

2000 ◽  
Vol 15 (5) ◽  
pp. 1145-1153 ◽  
Author(s):  
N. Nagendra ◽  
V. Jayaram
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Steady State ◽  
Crack Growth ◽  
Volume Fraction ◽  
Void Nucleation ◽  
Matrix Composition ◽  
Al Alloy ◽  
Constraint Factor ◽  
The Matrix

The role of matrix microstructure on the fracture of Al-alloy composites with 60 vol% alumina particulates was studied. The matrix composition and microstructure were systematically varied by changing the infiltration temperature and heat treatment. Characterization was carried out by a combination of metallography, hardness measurements, and fracture studies conducted on compact tension specimens to study the fracture toughness and crack growth in the composites. The composites showed a rise in crack resistance with crack extension (R curves) due to bridges of intact matrix ligaments formed in the crack wake. The steady-state or plateau toughness reached upon stable crack growth was observed to be more sensitive to the process temperature rather than to the heat treatment. Fracture in the composites was predominantly by particle fracture, extensive deformation, and void nucleation in the matrix. Void nucleation occurred in the matrix in the as-solutionized and peak-aged conditions and preferentially near the interface in the underaged and overaged conditions. Micromechanical models based on crack bridging by intact ductile ligaments were modified by a plastic constraint factor from estimates of the plastic zone formed under indentations, and are shown to be adequate in predicting the steady-state toughness of the composite.

Microscopic Phase-Field Simulation of the Process of Middle Heat Treatment of Ni-Cr-Al Alloy

2011 ◽  
Vol 80-81 ◽  
pp. 36-39
Author(s):  
Zhong Chu ◽  
Guo Qun Zhao
Keyword(s):  
Heat Treatment ◽  
Phase Field ◽  
Field Model ◽  
Volume Fraction ◽  
Phase Field Model ◽  
Nucleation And Growth ◽  
Al Alloy ◽  
Precipitation Mechanism ◽  
Microscopic Phase Field Model ◽  
Strengthening Phases

The effect of the middle heat treatment+aging(1323K+1073K) for the precipitation mechanism and volume fraction of Ni-11at.%Cr-17at.%Al ternary alloy are studied based on microscopic phase-field model. The results show that the precipitation mechanism is non-classical nucleation and growth for the alloy at middle heat treatment, and the congruent ordering and spinodal decomposition mechanism occur at single-stage aging. The larger precipitation strengthening phases are obtained, the volume fraction of ordering phases and the averaged ordering parameter are higher, and the incubation period prolongs after the middle heat treatment.

Effect of Heat-Treatment Time on Microstructure and Mechanical Properties of Mg-5Gd-2Y-2Zn-0.5Zr Alloy

2012 ◽  
Vol 482-484 ◽  
pp. 1384-1389 ◽  
Author(s):  
Ling Gang Meng ◽  
Can Feng Fang ◽  
Peng Peng ◽  
Nai Pu Li ◽  
Qiong Zhu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Treatment Time ◽  
Time Range ◽  
Lpso Phase ◽  
High Temperature Heat Treatment ◽  
Lpso Structure ◽  
The Matrix ◽  
New Type ◽  
The Stability

Microstructure evolution of Mg-5Gd-2Y-2Zn-0.5Zr alloy during high temperature heat-treatment at 500°C in the time range 10-70h was investigated. The results show that after adding the element Y, the as-cast Mg-5Gd-2Y-2Zn-0.5Zr alloy forms the Mg12Zn(Y,Gd) phase with 18R-LPSO structure at the grain boundary. During heat-treatment at 500°C, the stability of 18R-LPSO structure is weakened by Gd atoms, parts of LPSO phases dissolve gradually into the matrix with time prolonged and a new type Mg(Y,Gd)Zn phase come into being. LPSO phase in the grain boundary can ensure the ultimate tensile strength and elongation of the alloy, and effect of dissevering on the LPSO phase by Mg(Gd,Y)Zn phase results the decrease of UTS and elongation.

Reinforcement of 2124 Al Alloy with Low Micron SiC and Nano Al2O3 via Solid-State Forming

2015 ◽  
Vol 828-829 ◽  
pp. 172-178
Author(s):  
Zizo Gxowa ◽  
Sigqibo Templeton Camagu ◽  
Gonasagren Govender ◽  
Manuel Filipe Pereira
Keyword(s):  
Grain Boundaries ◽  
Metal Matrix ◽  
Volume Fraction ◽  
Al Alloy ◽  
Matrix Composites ◽  
Intergranular Cracking ◽  
Powder Metallurgical Process ◽  
Hardness Tests ◽  
Mode Of Failure ◽  
The Matrix

A powder metallurgical process was used to fabricate Metal Matrix Composites (MMCs). A 2124 aluminium alloy was reinforced with 5 and 10 vol.% of Al2O3(40-70nm) to form Metal Matrix Nano Composites (MMNCs) as well as 10 and 15 vol.% of SiC (1-10µm) to fabricate low micron MMCs. It was observed that the nano-sized Al2O3particles were evenly dispersed in the aluminium matrix while a lot of loose SiC particles settled on the grain boundaries in the low micron MMCs. The relative density of all the composites increased due to sintering, however full densification was not achieved. This result was attributed to the hindered motion of dislocations, grains and grain boundaries by reinforcing particles. The 2124-Al/10%-SiC composite was cold extruded and the extruded part fractured. A metallographic evaluation was carried out and it was deduced that the mode of failure was intergranular cracking. Hardness tests performed after sintering indicated that hardness increased with an increase in volume fraction of reinforcement in the matrix. Annealing of the extruded part resulted in a decrease in hardness.

Grain Boundary Precipitate Density as a Function of Time and Misorientation in an Al-5 WT% Cu Alloy

1993 ◽  
Vol 319 ◽  
Author(s):  
M. A. Cantrell ◽  
G. J. Shiflet
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Treatment Time ◽  
Boundary Plane ◽  
Heat Treatment Time ◽  
Boundary Structure ◽  
Plane Orientation ◽  
Cu Alloy ◽  
Grain Boundary Plane ◽  
Precipitate Density

AbstractThe variation of θ (CuAI2) precipitate density as a function of heat treatment time and grain boundary misorientation was investigated in an Al-5 wt % Cu alloy. In this study, precipitate densities have been quantitatively linked to grain boundary structure. It was found that, for a given heat treatment time, the precipitate density varied in a reproducible manner (108 to 1010 ppts/cm2) as a function of misorientation between the grains (20 to 60 degrees). Additionally, misorientation was found to be the most important factor governing the precipitate density at a given grain boundary. The grain boundary plane orientation played a secondary role in determining the precipitate density. Bollmann O-lattice modeling allows comparison of the relative effects of grain boundary plane orientation relative to the misorientation between grains.

Investigation on Purification and Degassing of TiB2/Al Composite Fabricated by LSM Method

2007 ◽  
Vol 353-358 ◽  
pp. 3051-3054 ◽  
Author(s):  
Hong Gu ◽  
Yong Zhi Zou ◽  
Zheng Bin Xu ◽  
Jian Min Zeng
Keyword(s):  
Image Analysis ◽  
Grain Boundary ◽  
Volume Fraction ◽  
Inert Gas ◽  
X Ray Diffraction ◽  
X Ray ◽  
Al Composite ◽  
The Matrix ◽  
Tib2 Particles ◽  
Cast Condition

In the present paper, TiB2/Al composite with 5% volume fraction of TiB2 was fabricated by LSM method. The effects of purification and degassing methods on TiB2/Al composite were examined by means of X-ray diffraction (XRD) and image analysis. Hydrogen contents in the molten composites were detected and compared among flux, inert gas and vacuum purification processes. The experimental results indicate that under general cast condition a majority of the TiB2 particles distribute on grain boundary, and only a few particles disperse within grains. The flux and vacuum purifications have no virtual impact on the distribution of TiB2 and the fraction of TiB2 remains the same after purification. However, degassing with inert gas will be detrimental; the TiB2 particles will be separated and removed from the matrix. The hydrogen contents for flux, inert gas and vacuum processes are 0.15ml/100g/Al, 0.12ml/100g/Al and 0.12ml/100g/Al respectively.

Finite Element Simulation and Optimisation of Ageing Precipitation in Nickel Base Superalloys with a Low Gamma-Prime (g’) Volume Fraction

2011 ◽  
Vol 172-174 ◽  
pp. 881-886 ◽  
Author(s):  
Franck Tancret ◽  
Philippe Guillemet ◽  
Florent Fournier Dit Chabert ◽  
René Le Gall ◽  
Jean François Castagné
Keyword(s):  
Heat Treatment ◽  
Finite Element ◽  
Volume Fraction ◽  
Nucleation And Growth ◽  
Thermodynamic Quantities ◽  
Gamma Prime ◽  
The Matrix ◽  
Element Approach ◽  
Automatic Heat ◽  
Nickel Base

A finite element approach is used to simulate the precipitation of Ni3(Al,Ti) intermetallics in nickel-based superalloys containing a low volume fraction of spherical g’ precipitates, in which precipitation occurs following nucleation and growth mechanisms. Classical differential equations of nucleation and growth are implemented in the software Comsol (formerly Femlab), to compute the number of precipitates per unit volume and their mean size. Another originality of the model is the use of thermodynamic quantities coming from phase diagram computations (Thermo-Calc), like the temperature variation of the equilibrium g’ volume fraction, and the evolution of the concentration of g’ forming elements (Al, Ti) in the matrix with the volume fraction of precipitates. Once adjusted to experiment in the case of isothermal ageings, the model can be used to simulate precipitation during complex thermal histories. Finally, automatic heat treatment optimisation procedures are proposed and tested, which can reduce heat treatment times by a factor of more than five.

Effect of carbides on the wear resistance of white cast iron alloyed with 12.7 wt.-% Cr and nickel

2020 ◽  
Vol 62 (8) ◽  
pp. 788-792
Author(s):  
Tanju Teker ◽  
S. Osman Yilmaz ◽  
Tekirdağ Teker
Keyword(s):  
Heat Treatment ◽  
Wear Resistance ◽  
Cast Iron ◽  
White Cast Iron ◽  
Volume Fraction ◽  
High Wear Resistance ◽  
Homogeneous Distribution ◽  
Nickel Concentration ◽  
Carbide Size ◽  
Wear Tests

Abstract White cast iron with about 12.7 wt.-% chromium was alloyed with Ni, W and Mo for heat treatment applications. Heat treatments were performed at a range of 850-1050 °C for 1 h in order to distribute M7C3 carbides homogeneously in an environment of high wear resistance. The contents of the C, Cr, Ni, Mo, Mn and Si elements selected for the alloys were similar, though a 6 wt.-% nickel concentration was chosen. Microstructural changes in the specimens were examined by scanning electron microscopy (SEM) and optical microscopy (OM). Macro-hardness, average carbide size and volume fraction were analyzed. Wear tests were carried out under different loads of 10, 20 and 30 N. It was seen that heat treatment changed the carbide size and homogeneous distribution of the carbides. Moreover, the addition of nickel to HCrWCI increased fracture toughness and reduced the wear rate.

Modeling the Microstructural and Yield Strength Evolution of an Age-Hardenable Al Alloy for High Temperature Applications

2016 ◽  
Vol 879 ◽  
pp. 380-385 ◽  
Author(s):  
Marco Colombo ◽  
Elisabetta Gariboldi ◽  
Paola Bassani ◽  
Mihaela Albu ◽  
Ferdinand Hofer
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Yield Strength ◽  
Elevated Temperatures ◽  
Age Hardening ◽  
Homogeneous Distribution ◽  
Al Alloy ◽  
Physically Based ◽  
The Matrix ◽  
Physically Based Models

The mechanical properties of Al alloys are strongly affected by their microstructure: the size and shape of precipitates, their homogeneous distribution and their coherency with the matrix are of primary importance for an effective strengthening of the alloys at room and elevated temperatures. Physically-based models are powerful tools to predict the influence of the mentioned parameters on the mechanical properties of the alloy after age hardening, and also to predict the effect of high temperature service conditions on microstructure evolution. Scope of this work is to model the dimensional kinetic evolution of plate shaped precipitates of an Al-based alloy during aging and after different overaging times at elevated temperature, and use these results to estimate the alloy yield strength. The alloy strengthening response is due to three terms, linearly summed: the intrinsic strength of Aluminum, the contribution from solute in solid solution and the contribution arising from precipitates. The consistency of the model is verified with experimental data obtained from a 2014 Al alloy.

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