Microstructure and Fatigue Properties of Aero Aluminum Alloy Repaired by Laser Melt Casting

2011 ◽  
Vol 314-316 ◽  
pp. 1871-1875 ◽  
Author(s):  
Chang Liang Lu ◽  
Fang You Hu ◽  
Xu Ren Huang ◽  
De Xian Yi ◽  
Ai Yong Cui ◽  
...  
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Composite Powder ◽  
Crystal Size ◽  
Axial Direction ◽  
Fatigue Properties ◽  
Crystallographic Axis ◽  
Al Matrix Composite ◽  
Al Matrix

The paper presents a study of renovation of aerial aluminum alloy (LY12CZ) by laser melt casting with Al matrix composite powder. The microstructure of the melt casting zone was investigated, and the fatigue contrast test was carried out between the repaired specimens and the undamaged specimens. It is found that the melt casting zone consists of equiaxed crystals and columnar crystals. The equiaxed crystals distribute in the deposited layer and the crystal size is about 3~4μm. The columnar crystals whose axial direction size comes to 30μm~40μm exist near the interface with its crystallographic axis perpendicular to the interface. The fatigue life of specimens repaired by laser melt casting was shorter than no-damage specimens to a large extant, because of the flaws in the deposited layer engendered the origins of cracks; the columnar shape grains at the bottom of casting zone were easy to split under the tensile stress; the residual stress after the melt casting accelerated the initiation and growth of the cracks.

Effect of sand-blasting on fatigue properties of 7N01 aluminum alloy

2019 ◽  
Vol 33 (01n03) ◽  
pp. 1940003 ◽  
Author(s):  
Shali Qu ◽  
Min Yu
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
High Speed ◽  
Fatigue Properties ◽  
Sand Particle ◽  
Surface Zone ◽  
Sand Blasting ◽  
Depth Direction ◽  
High Speed Trains

Certain high-speed trains often suffer from the erosion of wind-drift sand during the serving period. The present paper simulated this sand-blasting process with consideration of sand-blasting pressure, angle, distance and sand particle size representing different natural conditions. Results show that the grit size has the greatest influence on roughness and residual stress of the 7N01 aluminum alloy based on the orthogonal test. The samples after low intensity sand-blasting (LISB) were characterized by micro-hardness, surface morphology and fatigue test. Results show that the surface of the blasted sample was severely impinged in form of extruded ridges crater-like morphology, representing different roughness values. The LISB causes a similar spoon shape residual stress distribution along the depth direction and it also increases the hardness of the surface zone. Finally, the residual compressive stress plays an important role in the improvement of the fatigue life, and the increase of roughness can seriously shorten the fatigue life.

scholarly journals Effect of Cavitation Peening on Fatigue Properties in Friction Stir Welded Aluminum Alloy AA5754

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 59
Author(s):  
Hitoshi Soyama ◽  
Michela Simoncini ◽  
Marcello Cabibbo
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Compressive Residual Stress ◽  
Diffraction Method ◽  
Fatigue Properties ◽  
Surface Residual Stress ◽  
Friction Stir ◽  
Sheet Cavitation ◽  
Lightweight Metals

Friction stir welding (FSW) is an attractive solid-state joining technique for lightweight metals; however, fatigue properties of FSWed metals are lower than those of bulk metals. A novel mechanical surface treatment using cavitation impact, i.e., cavitation peening, can improve fatigue life and strength by introducing compressive residual stress into the FSWed part. To demonstrate the enhancement of fatigue properties of FSWed metal sheet by cavitation peening, aluminum alloy AA5754 sheet jointed by FSW was treated by cavitation peening using cavitating jet in air and water and tested by a plane bending fatigue test. The surface residual stress of the FSWed part was also evaluated by an X-ray diffraction method. It was concluded that the fatigue life and strength of FSWed specimen were improved by cavitation peening. Whereas the fatigue life at σa = 150 MPa of FSWed specimen was about 1/20 of the bulk sheet, cavitation peening was able to extend the fatigue life of the non-peened FSW specimen by 3.6 times by introducing compressive residual stress into the FSWed part. This is the first paper to demonstrate the improvement of fatigue properties of FSWed metallic sheet by cavitation peening.

The Fatigue Properties of Laser Shock Processed Aluminum Alloy 7050

2007 ◽  
Author(s):  
Shikun Zou ◽  
Ziwen Cao
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Plastic Strain ◽  
Base Material ◽  
Fatigue Properties ◽  
Hole Drilling ◽  
Drilling Process ◽  
Laser Peening ◽  
Laser Shock

In order to develop the application of laser shock processing (also named laser peening or LSP in short) as a strengthening technology for 7050 aluminum alloy fastener holes, the fatigue properties of laser shock-processed aluminum alloy specimens were investigated. At first, the dislocation density and surface residual stress induced in the shock affected zone was characterized and compared with that of the base material. Then, the fatigue specimens with stress-concentration hole (notch) were treated by LSP. The fatigue life of LSP-treated specimens were measured and compared with that of specimens made from base material without LSP. Fatigue tests were taken under special flight spectrum loading condition for mid-airframe. The results indicated that laser peening improved the fatigue life of all specimens tested. Specimens treated by LSP before hole-drilling had longer fatigue life than those specimens treated by LSP after hole-drilling. At last, the difference of both sequences was investigated by analyzing the plastic strain and residual stress induced by LSP. LSP induced both plastic strain and deformation at the surface layer. The plastic strain induced by LSP was shown to produce harmful orifices with sharp-angle near the edge of hole. The residual stress induced by LSP appears to remain compressive even after the hole-drilling process. In average, the fatigue life of specimens treated by LSP before hole-drilling was found to be 173% longer than that of untreated samples and approaching the life enhancement factor demonstrated by rod extrusion method (on specimens with large diameter holes).

Fatigue Property Test and Numerical Simulation Analysis of 2524 Aluminum Alloy by Laser Shock Process

2020 ◽  
Vol 842 ◽  
pp. 265-271
Author(s):  
Song Bai Li ◽  
Xiang Li
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Simulation Analysis ◽  
Laser Energy ◽  
Stress Test ◽  
Fatigue Properties ◽  
Laser Shock ◽  
Shock Process

Effects of laser shock peening on the fatigue properties of 2524 aluminum alloy were investigated by laser shock test, residual stress test and fatigue crack growth test respectively. The results show that the maximum residual stress is -220MPa at a distance of 1.1mm from the spot center after LSP (laser energy of 6.26J). The distribution of residual stress was simulated by Abaqus software, and the numerical simulation results were in good agreement with the experimental results. Compared with the untreated specimens, the fatigue life of the shocked specimens was increased by 32%. Fatigue fracture morphologies of the final rupture zone also show that more dimples of significantly larger depth and size occur. The fatigue life of 2524 aluminum alloy can be effectively extended by laser shock process (LSP).

Core-shell structural iron based met al matrix composite powder for laser cladding

2021 ◽  
pp. 160127
Author(s):  
Zhen Wang ◽  
Mixue Tan ◽  
Jiang Wang ◽  
Jing Zeng ◽  
Fengjun Zhao ◽  
...  
Keyword(s):  
Matrix Composite ◽  
Laser Cladding ◽  
Composite Powder ◽  
Core Shell ◽  
Iron Based ◽  
Structural Iron ◽  
Al Matrix Composite ◽  
Al Matrix

scholarly journals Fatigue Life Improvement of the High Strength Steel Welded Joints by Ultrasonic Impact Peening

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 619 ◽  
Author(s):  
Ján Lago ◽  
Libor Trško ◽  
Michal Jambor ◽  
František Nový ◽  
Otakar Bokůvka ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Welded Joints ◽  
Compressive Residual Stress ◽  
High Strength ◽  
Fatigue Properties ◽  
Low Alloy Steel ◽  
Residual Stress Field ◽  
Near Surface ◽  
Life Improvement

Ultrasonic impact peening was applied on welded joints manufactured from Strenx 700 MC high strength low alloy steel with the aim to improve the fatigue properties. Three different surface treatment parameters were tested, which resulted in transformation of the near-surface tensile residual stresses in the weld metal and heat affected zone to compressive residual stress field, while maximal values from −400 MPa up to −800 MPa were reached. The highest fatigue life improvement was reached by the double peening with the 85 N contact force, where the fatigue limit for N = 108 cycles increased from 370 MPa to 410 MPa.

The Effects of Machined Workpiece Surface Integrity on the Fatigue Life of TC21 Titanium Alloy

2012 ◽  
Vol 503-504 ◽  
pp. 382-389 ◽  
Author(s):  
Dong Xing Du ◽  
Dao Xin Liu ◽  
Yu Feng Sun ◽  
Jin Gang Tang ◽  
Xiao Hua Zhang
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Surface Integrity ◽  
Surface Profile ◽  
Fatigue Properties ◽  
Profile Measurement ◽  
Micro Hardness ◽  
Finish Turning ◽  
Rough Turning

In this paper, the influence of different machining methods (including rough turning, finish turning, and longitudinal polishing after finish turning) on rotating bending fatigue properties of TC21 which belonged to a new ultra high strength titanium alloy was studied. The influence of machining methods on surface integrity of TC21 titanium alloy was measured by using surface profile measurement, scanning electron microscopy, metallography microscope, micro-hardness instrument and X-ray diffraction residual stress analyzer. And fatigue fractography of specimens was further investigated. Then the mechanism of fatigue resistance which was affected by machining surface integrity was discussed. The results indicated that the fatigue life of finish turning and longitudinal polishing after finish turning was increased 3.96 times and 17.34 times compared with rough turning, respectively. The machining surface integrity had important influence on fatigue property of TC21 titanium alloy, which caused by the differences of surface roughness and texture as the dominant factors, and then the variation in surface micro-hardness, metallographic microstructure and the surface residual stress were not the main factors on three above-mentioned machining methods. By using longitudinal polishing after finish turning processing method for preparation of TC21 titanium alloy parts could ensure good surface integrity and excellent fatigue performance.

scholarly journals Sequential Effects of Deep Rolling and Post-Weld Heat Treatment on Surface Integrity of AA7075-T651 Aluminum Alloy Friction Stir Welding

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3510 ◽  
Author(s):  
Adirek Baisukhan ◽  
Wasawat Nakkiew
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Friction Stir Welding ◽  
Surface Integrity ◽  
Post Weld Heat Treatment ◽  
Deep Rolling ◽  
Friction Stir ◽  
Weld Heat

The aim of this research is to investigate the sequence of processes for improving the welded surface integrity of AA7075-T651 aluminum alloy joined by friction stir welding (FSW). The improvement processes that will be investigated herein include mechanical surface improvement with deep rolling (DR) and post-weld heat treatment (PWHT). Therefore, this study investigated welded surface integrity, which comprises residual stress, microhardness, surface roughness, microstructure, and fatigue life (screening). The experiment consists of three sets of combinations. In the first set, only FSW was applied; in the second set, FSW was applied, followed by DR, and then PWHT processes (FSW-DR-PWHT); and in the last set, FSW was applied, followed by PWHT, and then DR processes (FSW-PWHT-DR). Fatigue testing was carried out by undertaking a four-point bending test using a bending stress of approximately 300 MPa with a test frequency of 2.5 Hz at room temperature and stress ratio R = 0. The study found that residual stress plays an important role in the fatigue life. Finally, the fatigue test showed that FSW workpieces subject to the PWHT process followed by the DR process (FSW-PWHT-DR) had the highest fatigue life, with an increase of 239% when compared with unprocessed FSW workpieces.

scholarly journals Investigation of residual stress, stress relaxation and work hardening effects induced by shot peening on the fatigue life of AA 6005-T6 aluminum alloy

2020 ◽  
Vol 6 (12) ◽  
pp. 1265i2 ◽  
Author(s):  
Martin Ferreira Fernandes ◽  
Marcelo Augusto Santos Torres ◽  
Maria da Penha Cindra Fonseca ◽  
Carlos Antonio Reis Pereira Baptista
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stress Relaxation ◽  
Shot Peening ◽  
Work Hardening

scholarly journals The Effect of Laser Peening without Coating on the Fatigue of a 6082-T6 Aluminum Alloy with a Curved Notch

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 728 ◽  
Author(s):  
Enrico Troiani ◽  
Nicola Zavatta
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Behavior ◽  
Surface Hardness ◽  
Element Model ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Laser Peening Without Coating

Laser shock peening has established itself as an effective surface treatment to enhance the fatigue properties of metallic materials. Although a number of works have dealt with the formation of residual stresses, and their consequent effects on the fatigue behavior, the influence of material geometry on the peening process has not been widely addressed. In this paper, Laser Peening without Coating (LPwC) is applied at the surface of a notch in specimens made of a 6082-T6 aluminum alloy. The treated specimens are tested by three-point bending fatigue tests, and their fatigue life is compared to that of untreated samples with an identical geometry. The fatigue life of the treated specimens is found to be 1.7 to 3.3 times longer. Brinell hardness measurements evidence an increase in the surface hardness of about 50%, following the treatment. The material response to peening is modelled by a finite element model, and the compressive residual stresses are computed accordingly. Stresses as high as −210 MPa are present at the notch. The ratio between the notch curvature and the laser spot radius is proposed as a parameter to evaluate the influence of the notch.

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