Mechanical Analysis of Stretch-Bend Process

Ｍｏｄｅｒｎｉｚｅｄｐｒｏｄｕｃｔｉｏｎｏｆｗｉｄｅｓｔｒｉｐｈａｓｐｕｔｈｉｇｈｅｒｒｅｑｕｉｒｅｍｅｎｔｓｔｏｐｒｏｃｅｄｕｒｅｓｂｅｆｏｒｅａｎｄａｆｔｅｒｒｏｌｌｉｎｇ．Ｔｅｎｓｉｏｎｌｅｖｅｌｅｒｈａｓｂｅｅｎｗｉｄｅｌｙｕｓｅｄｂｅ－ｃａｕｓｅｏｆｉｔｓｆｕｎｃｔｉｏｎｓｏｆｓｈａｐｅｃｏｎｔｒｏｌｌｉｎｇａｎｄｄｅｓｃａｌｉｎｇ．Ｈｏｗｅｖｅｒ，ｉｔｓｗｏｒｋｉｎｇｅｆｆｉｃｉｅｎｃｙｉｓｎｏｔｓａｔｉｓｆａｃｔｏｒｙ．Ｔｈｅｒｅａｓｏｎｌｉｅｓｉｎｔｈｅｌａｃｋｏｆｒｅｃｏｇｎｉ…     

Mechanical Activation-Assisted Synthesis of Nd-BaPbO3

ThesimpleperovskiteBaPbO3hasbeenreportedtohavehighelectricalconductivityandorthorhombicsymmetry[1～ 3] .Matherssetal .[4 ] reportedthehighconductivityofthismaterialoriginatesfromtheforma tionofabroadbandduetomixingoflead 6sandoxy gen 2pstates .Substitutionand/ornonstoichiometryinBaPbO3induceinterestingelectricalproperties .Forexample ,Sleightetal .[3] foundthesuperconductivityofBaPb1-xBixO3intherangeofx =0 .0 5～ 0 .3in1975 .IncreasingattentionhasbeenfocusedonBaP bO3asacomponentofthemate…     

Mechanical properties of porous Fe–Al intermetallics

Abstract

The effects of Al content and porosity on the mechanical properties of porous Fe–Al intermetallics, particularly at high temperatures, were determined using scanning electron microscopy, X-ray diffraction and mechanical properties testing. Results show that the optimal mechanical properties are achieved at 20 to 30 wt-%Al content. The tensile and bend strengths decrease with increasing Al content at 35 to 60 wt-%Al content. The quantitative relationship between porosity and strength for porous Fe–Al intermetallics can be described as σ_b?=?181(1?θ)^3.3. The strength of porous Fe–Al intermetallics increases at medium temperature with the increase in temperature from room temperature. The maximum tensile strength (50.2 MPa) is achieved at 600°C, which is almost 36.8% higher than that at room temperature.     

Mechanical properties of Metals and Alloys (Ⅱ)

1.The tesile test (cont' d) Because of necking, the capacity of the ma-terial for plastic deformation in tension, i. e.the ductility, is not truly indicated by thestrain to fracture measured along the gaugelength. A longer gauge length would give asmaller value. A better measure of ductility isthe reduction of area at the narrowest part of theneck. This can be expressed as a logarithmicstrain in the form ln (A_0/A_1) where A_0 andA_1 are the initial and final areas. In an ideallyductile material a total reduction of area occurs,     

Mechanical behavior of a fine-grained duplex γ-TiAl alloy

The mechanical behavior of a fine-grained duplex γ-TiAl alloy was studied in compression at strain rates ranging from 0.001 to 2000 s⁻¹ and temperatures from −196°C to 1200°C. The temperature dependence of the yield and flow stresses is found to depend on the strain rate. At strain rates of 0.001 and 0.1 s⁻¹, the yield stress decreases as the temperature increases, with a plateau between 600°C and 800°C. At strain rates of 35 and 2000 s⁻¹, the yield stress exhibits a positive temperature dependence at temperatures above 600°C; however, postyield flow stresses exhibit a reduced temperature dependency. The work-hardening rate decreases dramatically with temperature at low and high temperatures, with a plateau occurring at intermediate temperatures for all strain rates. The work-hardening-rate plateau is seen to extend to higher temperatures as the strain rate increases. The strain-rate sensitivity at strain rates of 0.1 s⁻¹ and greater is lower than 0.1, although it increases slightly with temperature. At 0.001 s⁻¹, the strain-rate sensitivity increases dramatically at high temperatures (equal to 4.5 at 1200°C). The anomalous (positive) temperature dependence of the yield stress at high strain rates (>1 s⁻¹) and high temperatures (>600°C) is explained via a dislocation-jog pinning mechanism. The negative temperature dependence of the yield stress at low strain rates (<1 s⁻¹) and high temperatures (>900°C) is though to be due to a thermally activated dislocation-jog climb process in the grain interiors and/or deformation and recovery processes at/near grain boundaries. The decreased anomalous temperature dependence of the flow stress at high strain rates and high temperatures is ascribed to dynamic recovery promoted by adiabatic heating. Z. JIN, formerly Technical Staff Member, Materials Science and Technology Division, Los Alamos National Laboratory     

Mechanical properties of Metals and Alloys (Ⅰ)

1. The tensile test The mechanical properties of a metal are usually measured in a tensile test. A straight rod or strip is gripped at its ends, which are usually enlarged into shoulders to strengthen them, and it is then pulled axially by a gradually increasing tensile force. The shoulders taper smoothly from the grips to the geometrically uniform central section of the test bar, along which is marked a     

Mechanical behavior of a fine-grained duplex γ-TiAl alloy

The mechanical behavior of a fine-grained duplex γ-TiAl alloy was studied in compression at strain rates ranging from 0.001 to 2000 s⁻¹ and temperatures from −196 °C to 1200 °C. The temperature dependence of the yield and flow stresses is found to depend on the strain rate. At strain rates of 0.001 and 0.1 s⁻¹, the yield stress decreases as the temperature increases, with a plateau between 600 °C and 800 °C. At strain rates of 35 and 2000 s⁻¹, the yield stress exhibits a positive temperature dependence at temperatures above 600 °C; however, postyield flow stresses exhibit a reduced temperature dependency. The work-hardening rate decreases dramatically with temperature at low and high temperatures, with a plateau occurring at intermediate temperatures for all strain rates. The workhardening-rate plateau is seen to extend to higher temperatures as the strain rate increases. The strain-rate sensitivity at strain rates of 0.1 s⁻¹ and greater is lower than 0.1, although it increases slightly with temperature. At 0.001 s⁻¹, the strain-rate sensitivity increases dramatically at high temperatures (equal to 4.5 at 1200 °C). The anomalous (positive) temperature dependence of the yield stress at high strain rates (>1 s⁻¹) and high temperatures (>600 °C) is explained via a dislocation-jog pinning mechanism. The negative temperature dependence of the yield stress at low strain rates (<1 s⁻¹) and high temperatures (>900 °C) is thought to be due to a thermally activated dislocation-jog climb process in the grain interiors and/or deformation and recovery processes at/near grain boundaries. The decreased anomalous temperature dependence of the flow stress at high strain rates and high temperatures is ascribed to dynamic recovery promoted by adiabatic heating.     

Effect of Yttrium on Mechanical Properties and Microstructure of Ceramets

ＥｆｆｅｃｔｏｆＹｔｔｒｉｕｍｏｎＭｅｃｈａｎｉｃａｌＰｒｏｐｅｒｔｉｅｓａｎｄＭｉｃｒｏｓｔｒｕｃｔｕｒｅｏｆＣｅｒａｍｅｔｓＬｉｕＮｉｎｓ（刘宁）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｅｒｉｎｇ，ＡｎｈｕｉＩ...     

Microstructure and Mechanical Properties of TRIP Steel with Annealed Martensite

The microstructure and mechanical properties of cold rolled TRIP steel containing C 0.2, Si 0.5, Mn 1.5, A1 1.3, and Nb-kV 0.13 （mass%） with annealed martensite （TAM steel） were investigated using optical microscopy, field emission gun scanning electronic microscope （FEG SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, and mechanical testing. The mierostructure of the TAM steel mainly consisted of polygonal ferrite, bainite, annealed martensite and retained austenite. The martensite after annealing did not spheroidize, which consisted of annealed lath martensite structure and interlath second phase. Compared with the traditional TRIP steel with polygonal ferrite matrix （TPF steel）, the TAM steel has more excellent elongation rate over 32%. The TAM steel also has better strain hardening behavior than the TPF steel. The excellent elongation and strain harden- ing behavior of TAM steel result from high retained austenite stability of the TAM steel, which is attributed to its fine distribution and medium strength ratio of second phase to matrix.     

Formation and Sintering Behavior of Nanocrystalline Fe-Ni Powder by Mechanical Alloying

Thepotentialapplicationofnanostructuredma terialsusedasnovelstructuralorfunctionalengi neeringmaterialslargelydependsontheconsolida tionofpowdersbywhichthebulknanostructuredsolidsaremade .Theretentionofthemetastablemi crostructureintheconsolidationprocessismandato ryforpreservingthesuperiormechanical,electricalorcatalyticpropertiesofthematerial.Severalau thorsshowedthatthepressure assistedsinteringisadequateforbothreachingfulldensityandprevent inggraingrowth ,besidesthenanostructuredmateri als…     

Preparation and Mechanical Properties of Misch Metal Based Bulk Metallic Glasses

Bulk metallic glasses(BMGs)have been devel-oped in many alloy systems during past decade.Among these systems,rare-earth(RE)metal-basedBMGs are ones of those found earliest and with betterglass forming ability(GFA).For example,La-basedBMGs were the first a…     

Mechanical properties of mostly-crystalline,rapid-quenched PdSiSb

The mechanical properties of some rapid-quenched, partly-amorphous (as-prepared) PdSiSb alloys have been studied. These alloys showed tensile strengths (fracture force/fracture surface area) of 58–232 kg/mm², depending on their amorphous fraction (0–6%). The alloy's high strengths are due to an unusual microstructure, which consists of fine ( < 1 μm) dendrites of a ductile, supersaturated solution of Si and Sb in f.c.c. Pd, embedded in an amorphous matrix. The role of the glassy matrix in the fracture process is discussed.     

Processing,Microstructure, and Mechanical Properties of B4C ― TiB2 Particulate Sintered Composites. Part II. Fracture and Mechanical Properties

The fracture response of pressureless sintered boron carbide ceramics containing 5-25 vol.% TiB₂ phase produced via the in-situ chemical reaction between B₄C, TiO₂ and elemental carbon was studied. Both strength and fracture toughness depend on TiB₂ volume fraction, reaching their maximum values of 500 MPa and 4.6 MPa·m^1/2, respectively, at 15 vol.% TiB₂. The observed increase in strength and fracture toughness was ascribed to the interaction between the propagating crack front and local thermal mismatch stress associated with TiB₂ particles. Induced circumferencial microcracking and crack impedance are discussed as the major toughening mechanisms. Spontaneous circumferencial microcracking due to thermal mismatch stress in TiB₂ particles was found to occur when the particle size exceeds its critical value. The theoretical interpretation of spontaneous circumferencial microcracking, toughening via induced microcracking, and crack impedance was justified experimentally.     

Mechanical multiple relaxation spectra in NbZeO alloys

Mechanical multiple relaxation data has been obtained by internal friction and frequency measurements in the temperature range of 300–600 K for NbZrO single crystal alloys, using a torsion pendulum of the inverted Kê-type operating at a frequency of oscillation of about 3.5 Hz. The experimental relaxation spectra were resolved into four constituent peaks of Debye type corresponding to the matrix-interstitial interactions, NbO, NbOO, NbOOO and to the substitutional-interstitial interaction, ZrO. These results and the estimated relaxation rate parameters of the processes point to the existence of more than one matrix-interstitial interaction in these alloys.     

Research on Mechanical Model of Material during Twin Roll Strip Casting Process

Ｉｎｔｈｅｔｗｉｎｒｏｌｌｓｔｒｉｐｃａｓｔｉｎｇｐｒｏｃｅｓｓ ,ｔｈｅｍｅｃｈａｎｉｃａｌｂｅｈａｖｉｏｒｏｆｃａｓｔｉｎｇｍａｔｅｒｉａｌｃａｎｇｒｅａｔｌｙｉｎｆｌｕｅｎｃｅｒｏｌｌｉｎｇｆｏｒｃｅ,ｗｈｉｌｅｒｏｌｌｉｎｇｆｏｒｃｅｉｓｒｅｌｅｖａｎｔｔｏｓｔｒｉｐｓｕｒｆａｃｅｑｕａｌｉ ｔｙ .Ｉｆｒｏｌｌｉｎｇｆｏｒｃｅｓｕｒｐａｓｓｅｓａｌｉｍｉｔｅｄｖａｌｕｅ ,ｔｈｅｈｅａｔｔｒａｎｓｆｅｒｆｒｏｍｓｔｒｉｐｔｏｃａｓｔｉｎｇｒｏｌｌｗｉｌｌｂｅｃｏｍｅｕｎｅｖｅｎａｌｏｎｇｓｔｒ…     

Intercritical Rolling Induced Ultrafine Lamellar Structure and Enhanced Mechanical Properties ofMedium-Mn Steel

The medium-Mn steel with ferrite and austenite structure was rolled in the intercritical region down to dif- ferent rolling reduction. The microstructure and mechanical properties of the rolled steels were investigated by scan- ning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. It was found that the ferrite and austenite structure gradually evolved into an ultrafine structure from the random directional lath structure to lamellar structure with lath longitudinal direction parallel to the rolling direction with increasing rolling strain. It was found that the thickness of the laths was gradually refined with increasing rolling strain. The lath thickness is about 0. 15 9m stored with high density dislocations and the austenite volume fraction of the steel is about 24% after 80% rolling reduction. Furthermore, it was interesting to find that yield strength, tensile strength and total elongation of the 80% rolled medium-Mn steel are about 1000 MPa, 1250 MPa and 24%, respectively, demonstrating an excellent combination of the strength and ductility. Based on the microstructure examination, it was proposed that the grain refinement of the medium-Mn steels could be attributed to the duplex structure and the low rolling temperature. Analysis of the relationship between the microstructure and the mechanical properties indicated that the high yield strength mainly resulted from the ultrafine grain size and the high density dislocation, but the improved ductili- ty may be attributed to the large fractions of austenite retained after intercritical rolling.