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1.
D. Storjohann O. M. Barabash S. A. David P. S. Sklad E. E. Bloom S. S. Babu 《Metallurgical and Materials Transactions A》2005,36(11):3237-3247
Microstructure evolutions and degradations of aluminum-metal-matrix composites during fusion welding were studied and compared
with thermodynamic calculations. In fusion welds of Al2O3-reinforced composites, the decomposition of Al2O3 was observed. In fusion welds of SiC whisker-reinforced composites, the decomposition of SiC to Al4C3+Si by reaction with molten aluminum occurred. These phenomena led to unacceptable fusion welds in aluminum metal-matrix composites.
Successful welds were produced in the same composites by friction stir welding (FSW). Significant reorientation of SiC whiskers
close to the boundary of the dynamically recrystallized and thermomechanically affected zone (TMAZ) was observed. The small
hardening in the dynamically recrystallized region was attributed to the presence of dislocation tangles in between SiC whiskers. 相似文献
2.
Ferritic steels are often used in thick-plate form. The feasibility of electron-beam welding such thick plates and the mechanical
properties of these welds were examined in a recent study. In this investigation, the microstructures of these thick-plate,
electron-beam welds were evaluated. The study was carried out on a 3Cr-1.5Mo-0.1V steel. Weld simulations were used to aid
in the study of the heat-affected zone (HAZ) microstructure. Such simulations allowed for a more reliable and detailed evaluation
of the variation in microstructure with distance from the fusion line. The structures were related to microhardness measurements
made across the width of the weld and the HAZ. The fusion zone and the immediately adjacent HAZ consisted of bainite platelets
with narrow films of retained austenite at many of the bainite platelet boundaries. Farther away from the fusion zone, the
structure was a two-phase mixture of bainitic platelets and ferrite produced by heating base metal between theAc
1 and theAc
3 temperatures. Still farther from the weld, the structure consisted of tempered bainite, with the degree of tempering decreasing
with distance from the fusion line. The bainite plus ferrite region and the tempered bainite section are associated with a
soft zone in the hardness profile across the weld. A postweld heat treatment (PWHT) was found to reduce the hardnesses of
the fusion zone, HAZ, and base material to relatively uniform levels. The structure across the weld and HAZ after a PWHT is
tempered bainite except in one section of the HAZ in which tempered bainite and ferrite coexist. 相似文献
3.
Weld metal grain structure and mechanical properties of the Ir-0.3 pct W alloy (DOP-26) doped with 60 ppm Th and 50 ppm Al
have been investigated by use of a gas tungsten arc (GTA) welding process. The fusion zone grain structure is strongly influenced
by heat input and puddle shape and therefore by the bead width. With increasing bead width from 2.5 to 3.7 mm, the grains
in the fusion zone show a sharp change in growth direction near the centerline region and develop a fine columnar structure
with grains growing parallel to the welding direction. Mechanical properties of the welds and base metal were characterized
by tensile and impact tests from 650 to 1150 °C. The ductility and fracture behavior of DOP-26 welds are sensitive to weld
bead width, postweld heat treatment, and weld-test orientation. The ductility of the welded specimens increases with increasing
test temperature and decreasing weld bead width. The transverse weld specimen with a wide-bead width (3.7 mm) has the lowest
impact ductility, and the longitudinal weld with a narrow-bead width (2.5 mm) has the highest elongation at all the test temperatures.
The impact ductility of the transverse weld specimen with the narrow-bead width falls between the limits. All the results
are discussed in terms of the fusion zone grain structure and fracture path of the welds. 相似文献
4.
Umar Mustafa Mukesh Chandra Sathiya Paulraj 《Transactions of the Indian Institute of Metals》2018,71(8):1975-1983
In this work, the influence of filler wire diameter on AA5083-H111 weldments was studied. For that, square butt joints were made using an AC square wave gas tungsten arc welding process with the addition of filler wires of diameter 1.2 and 2.4 mm separately. The experimental results revealed that changing the filler wire diameter influenced the bead geometry and a complete penetration was achieved in both welds. The weldment processed with smaller diameter filler wire consisted of a wider heat affected zone with recrystallized grains and a fusion zone with coarser grain structure, thus reducing the mechanical properties and corrosion resistance. However, the use of larger diameter filler wire assisted in faster torch speed, resulting in lower heat input and thus finer equiaxed grains were produced in fusion zone. Also, finer grains along with the dispersion of finer Al6(Fe,Mn) particles supported in obtaining the superior tensile and corrosion properties. 相似文献
5.
This study examines procedures for consistently producing sound (crack and void free) welds using the autogenous (without
filler metal) gas tungsten arc (GTA) welding process. Cast alloy Ti-48Al-2Cr-2Nb (at. pct) and extruded alloy Ti-46Al-2Cr-2Nb-0.9Mo
(at. pct) have been examined to determine if sound welds can be produced using autogenous GTA welding without any preheat.
Experimentation consisted of GTA spot welding samples of gamma titanium aluminide at weld current levels of 45, 55, 65, and
75 A for a duration of 3 seconds. For the cast alloy, current levels of 45, 55, and 65 A for 3 seconds produced similar fusion
zone microstructures, which consisted of a dendritic solidification structure. The fusion zone microstructure of the 75 A
for 3 seconds current level differed significantly from the lower current levels. It also consisted of a dendritic solidification
structure; however, the morphology was quite different. For the extruded alloy, current levels of 45 and 55 A for 3 seconds
produced fusion zone microstructures similar to the lower current level samples of the cast γ-TiAl, which consisted of a dendritic solidification structure. The fusion zone microstructures of the 65 and 75 A samples
were similar to each other, but they had a dendritic solidification structure of a different morphology than that of the 45
and 55 A samples. For both alloys at all current levels, microhardness profiles showed an increase in hardness from the base
metal to the fusion zone. There were no significant differences in the average fusion zone hardness as a function of increasing
current level. However, nanoindentation testing did show that certain phases and microconstituents in the fusion zone did
have significant variations in hardness in relation to the enrichment and depletion of chromium.
This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the
TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformations
Committees. 相似文献
6.
The microstructure and the mechanical properties were studied in bead-on-plate welds in a Ti-6Al-2V-1Mo alloy. The heat affected
zone (HAZ) and the fusion zone (FZ) consisted of very large primaryβ grains with theβ-phase transformed to martensite. A special bead-on-plate welding technique allowed independent measurement of the mechanical
properties of the HAZ and the FZ. Compared to the as-received (AR) material, the strength and ductility decreased in the weld.
The highest fatigue strength was found for the AR material followed by the HAZ and the FZ, whereas the ranking for fatigue
crack growth was opposite. 相似文献
7.
L. Liu L. Xiao J. C. Feng Y. H. Tian S. Q. Zhou Y. Zhou 《Metallurgical and Materials Transactions A》2010,41(10):2642-2650
Resistance spot welding of AZ31 magnesium alloys from different suppliers, AZ31-SA (from supplier A) and AZ31-SB (from supplier B), was studied and compared in this article. The mechanical properties and microstructures have been studied of welds made with a range of welding currents. For both groups of welds, the tension-shear fracture load (F C) and fracture toughness (K C) increased with the increase in welding current. The F C and K C of AZ31-SA welds were larger than those of AZ31-SB welds. The fracture surfaces of AZ31-SB welds were relatively flatter than those of AZ31-SA. Microstructural examination via optical microscope demonstrated that almost all weld nuggets comprised two different zones, the columnar dendritic zone (CDZ), which grew epitaxially from the fusion boundary, and the equiaxed dendritic zone (EDZ), which formed in the center of the nugget. The nature and extent of the CDZ seemed to be critical to the strength and toughness of spot welds because of its position adjacent to the inherent external circular crack-like notch of spot welds and the stress concentration in this region. The width and microstructure of the CDZ were different between AZ31-SA and AZ31-SB. The AZ31-SA alloy produced finer and shorter columnar dendrites, whereas the AZ31-SB alloy produced coarser and wider columnar dendrites. The width of the CDZ close to the notch decreased with the increase of current. The CDZ disappeared when the current was higher than a critical value, which was about 24 kA for AZ31-SA and 28 kA for AZ31-SB. The microhardness of the two base materials was the same, but within the CDZ and EDZ, the hardness was greater in AZ31-SA than AZ31-SB welds. It is believed that the different microstructures of spot welds between AZ31-SA and AZ31-SB resulted in different mechanical properties; in particular, K C increased with the welding current because of the improved columnar-to-equiaxed transition. 相似文献
8.
M. J. Cieslak T. J. Headley W. A. Baeslack 《Metallurgical and Materials Transactions A》1990,21(4):1273-1286
The possible microstructures resulting from both fusion and solid-state processing of Ti-26Al-11Nb at. pct (Ti-15Al-21Nb wt pct) have been determined. The particular microstructure produced was primarily a function of the cooling rate from theβ solvus. The most rapid cooling rate, associated with pulsed Nd:YAG (yttrium-aluminum-garnet) laser welding, resulted in a microstructure in which the high-temperatureβ underwent an ordering reaction on cooling to the CsCl (B2) crystal structure. Intermediate cooling rate (≈60 °C/s) specimens [characteristic of the fusion zone and heat-affected zone (HAZ) in arc welds] were found to undergo a complete transformation (no retainedβ observed) to an acicularα 2 microstructure. Electron microprobe and analytical electron microscopy (AEM) analyses revealed no statistically significant compositional dψerences spatially within this structure. These two observations suggest that the transformation reaction in this cooling rate regime involves, at least in part, a compositionally invariant shear component. Controlled slow cooling rate (0.1 °C/s) experiments produced Widmanstätten microstructures which were two-phase (α 2 +β). The retainedβ phase was observed to be highly enriched (≈35 wt pct) in Nb. The transformedα 2 exhibited a very low dislocation density. Solidification cracking of fusion welds was not observed. 相似文献
9.
Effect of thermal processing on the microstructure of Ti-26Al-11Nb: Applications to fusion welding 总被引:2,自引:0,他引:2
M. J. Cieslak T. J. Headley W. A. Baeslack 《Metallurgical and Materials Transactions A》1990,21(5):1273-1286
The possible microstructures resulting from both fusion and solid-state processing of Ti-26Al-11Nb at. pct (Ti-15Al-21Nb wt pct) have been determined. The particular microstructure produced was primarily a function of the cooling rate from theβ solvus. The most rapid cooling rate, associated with pulsed Nd:YAG (yttrium-aluminum-garnet) laser welding, resulted in a microstructure in which the high-temperatureβ underwent an ordering reaction on cooling to the CsCl (B2) crystal structure. Intermediate cooling rate (≈60 °C/s) specimens [characteristic of the fusion zone and heat-affected zone (HAZ) in arc welds] were found to undergo a complete transformation (no retainedβ observed) to an acicularα 2 microstructure. Electron microprobe and analytical electron microscopy (AEM) analyses revealed no statistically significant compositional dψerences spatially within this structure. These two observations suggest that the transformation reaction in this cooling rate regime involves, at least in part, a compositionally invariant shear component. Controlled slow cooling rate (0.1 °C/s) experiments produced Widmanstätten microstructures which were two-phase (α 2 +β). The retainedβ phase was observed to be highly enriched (≈35 wt pct) in Nb. The transformedα 2 exhibited a very low dislocation density. Solidification cracking of fusion welds was not observed. 相似文献
10.
Improved Resistance to Laser Weld Heat-Affected Zone Microfissuring in a Newly Developed Superalloy HAYNES 282 总被引:1,自引:0,他引:1
Gleeble thermomechanical simulation and microstrucutural analyses of laser beam weldability of a newly developed precipitation-hardened nickel-base HAYNES alloy 282 were performed to better understand the fundamental cause of heat-affected zone (HAZ) cracking and how to prevent the cracking problem in the material. Submicron size intergranular M5B3 particles are identified for the first time in the present work by transmission electron microscopy, and were found to be the primary cause of HAZ grain boundary liquation cracking in the alloy. Complete dissolution of the liquating M5B3 particles by preweld heat treatment exacerbated rather than reduced susceptibility to cracking, which could be attributed to nonequilibrium intergranular segregation of boron atoms, liberated by the complete dissolution of the boride particles, during cooling from heat treatment temperature. Consequently, to reduce the HAZ cracking, a preweld heat treatment that reduces the volume fraction of the M5B3 particles while minimizing nonequilibrium grain boundary boron segregation is necessary, and this is possible by heat treating the alloy at 1353?K to 1373 K (1080?°C to 1100 °C). Further improvement in cracking resistance to produce crack-free welds is achieved by subjecting the alloy to thermomechanically induced grain refinement coupled with the preweld heat treatment at 1353 K (1080 °C). A Gleeble hot ductility test showed that formation of the crack-free welds is unexplainable by mere reduction in grain size without considering the effect of grain refinement on intergranular liquid produced by subsolidus liquation of the M5B3 borides. 相似文献
11.
Liu L. Xiao L. Feng J.C. Tian Y.H. Zhou S.Q. Zhou Y. 《Metallurgical and Materials Transactions A》2010,41(10):2651-2661
Resistance spot welding of AZ31 magnesium alloys from different suppliers, AZ31-SA (from supplier A) and AZ31-SB (from supplier
B), was studied and compared in this article. The mechanical properties and microstructures have been studied of welds made
with a range of welding currents. For both groups of welds, the tension-shear fracture load (F
C) and fracture toughness (K
C) increased with the increase in welding current. The F
C and K
C of AZ31-SA welds were larger than those of AZ31-SB welds. The fracture surfaces of AZ31-SB welds were relatively flatter
than those of AZ31-SA. Microstructural examination via optical microscope demonstrated that almost all weld nuggets comprised
two different zones, the columnar dendritic zone (CDZ), which grew epitaxially from the fusion boundary, and the equiaxed
dendritic zone (EDZ), which formed in the center of the nugget. The nature and extent of the CDZ seemed to be critical to
the strength and toughness of spot welds because of its position adjacent to the inherent external circular crack-like notch
of spot welds and the stress concentration in this region. The width and microstructure of the CDZ were different between
AZ31-SA and AZ31-SB. The AZ31-SA alloy produced finer and shorter columnar dendrites, whereas the AZ31-SB alloy produced coarser
and wider columnar dendrites. The width of the CDZ close to the notch decreased with the increase of current. The CDZ disappeared
when the current was higher than a critical value, which was about 24 kA for AZ31-SA and 28 kA for AZ31-SB. The microhardness
of the two base materials was the same, but within the CDZ and EDZ, the hardness was greater in AZ31-SA than AZ31-SB welds.
It is believed that the different microstructures of spot welds between AZ31-SA and AZ31-SB resulted in different mechanical
properties; in particular, K
C increased with the welding current because of the improved columnar-to-equiaxed transition. 相似文献
12.
This study examines procedures for consistently producing sound (crack and void free) welds using the autogenous (without
filler metal) gas tungsten arc (GTA) welding process. Cast alloy Ti−48Al−2Cr−2Nb (at. pct) and extruded alloy Ti−46Al−2Cr−2Nb−0.9Mo
(at. pct) have been examined to determine if sound welds can be produced using autogenous GTA welding without any preheat.
Experimentation consisted of GTA spot welding samples of gamma titanium aluminide at weld current levels of 45, 55, 65, and
75 A for a duration of 3 seconds. For the cast alloy, current levels of 45, 55, and 65 A for 3 seconds produced similar fusion
zone microstructures, which consisted of a dendritic solidification structure. The fusion zone microstructure of the 75A for
3 seconds current level differed significantly from the lower current levels. It also consisted of a dendritic solidification
structure; however, the morphology was quite different. For the extruded alloy, current levels of 45 and 55 A for 3 seconds
produced fusion zone microstructures similar to the lower current level samples of the cast γ-TiAl, which consisted of a dendritic
solidification structure. The fusion zone microstructures of the 65 and 75 A samples were similar to each other, but they
had a dendritic solidification structure of a different morphology than that of the 45 and 55 A samples. For both alloys at
all current levels, microhardness profiles showed an increase in hardness from the base metal to the fusion zone. There were
no significant differences in the average fusion zone hardness as a function of increasing current level. However, nanoindentation
testing did show that certain phases and microconstituents in the fusion zone did have significant variations in hardness
in relation to the enrichment and depletion of chromium.
This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the
TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformations
Committees. 相似文献
13.
The investigation of the toughness properties in the heat-affected zone of submerged-arc welds performed on 20 to 30 mm thick plates made of normalized fine-grained structural steels with yield strengths of 280 to 480 N/mm2 established that the notched-bar impact energy produced in the heat-affected zone by means of a high heat input (t8/5 > 40s) can be improved by alloying with titanium. The titanium-alloyed steels display toughness properties in the heat affected zone that roughly correspond with the values of the base material, while the heat affected zone of titanium-free steels, when compared with the base material, displays appreciably inferior notched-bar impact energy values. 相似文献
14.
M. J. Cieslak J. J. Stephens M. J. Carr 《Metallurgical and Materials Transactions A》1988,19(3):657-667
The weldability and weld metal microstructure of Cabot Alloy 214 have been investigated with a variety of experimental and
analytical techniques. These include Varestraint hot crack testing, hot ductility testing, pulsed Nd:YAG laser welding, scanning
and analytical electron microscopy, electron microprobe analysis, and X-ray diffraction. A heat of Alloy 214 containing intentionally
alloyed B (0.003 wt pct) and Zr (0.07 wt pct) was much more sensitive to both fusion zone hot cracking as quantified by the
Varestraint test and to simulated heat-affected-zone (HAZ) cracking as quantified by hot ductility testing than a heat of
Alloy 214 containing no intentionally added B (0.0002 wt pct) or Zr (0.02 wt pct). Scanning electron microscopy of the high
B and Zr alloy showed the presence of dendritically-shaped, Zr-rich constituents in interdendritic regions in the gas-tungsten-arc
(GTA) welds. Electron microprobe analysis of these welds revealed a segregation pattern of Cr, Al, Mn, and Zr enrichment in
interdendritic regions and Ni and Fe enrichment in dendrite core regions. Analytical electron microscopy revealed the presence
of ZrX (X = B, C, N, O), M23C6, andγ′ in the fusion zone of GTA weld specimens,γ′ was also found in the as-received base metal and in the GTA weld HAZ. X-ray diffraction analysis of extractions from the
high B and Zr GTA weld metal also indicated the presence of a ZrX-type constituent. The results of this study are in qualitative
agreement with earlier work performed on alloys such as NIMONIC 90 and INCONEL 718∗ relative to the detrimental effect of B and Zr additions on fusion zone and HAZ hot cracking susceptibility.
Formerly with Sandia National Laboratories, Albuquerque, NM 相似文献
15.
CO2 laser beam welding of 6061-T6 aluminum alloy thin plate 总被引:1,自引:0,他引:1
Akio Hirose Kojiro F. Kobayashi Hirotaka Todaka 《Metallurgical and Materials Transactions A》1997,28(12):2657-2662
Laser beam welding is an attractive welding process for age-hardened aluminum alloys, because its low heat input minimizes
the width of weld fusion and heat-affected zones (HAZs). In the present work, 1-mm-thick age-hardened Al-Mg-Si alloy, 6061-T6,
plates were welded with full penetration using a 2.5-kW CO2 laser. Fractions of porosity in the fusion zones were less than 0.05 pct in bead-on-plate welding and less than 0.2 pct in
butt welding with polishing the groove surface before welding. The width of a softened region in the-laser beam welds was
less than 1/4 times that of a tungsten inert gas (TIG) weld. The softened region is caused by reversion of strengthening β″
(Mg2Si) precipitates due to weld heat input. The hardness values of the softened region in the laser beam welds were almost fully
recovered to that of the base metal after an artificial aging treatment at 448 K for 28.8 ks without solution annealing, whereas
those in the TIG weld were not recovered in a partly reverted region. Both the bead-on-plate weld and the butt weld after
the postweld artificial aging treatment had almost equivalent tensile strengths to that of the base plate. 相似文献
16.
Karl E. Dawson Gordon J. Tatlock Kuangnan Chi Peter Barnard 《Metallurgical and Materials Transactions A》2013,44(11):5065-5080
The effect of post-weld heat treatments (PWHTs) on the evolution of precipitate phases in dissimilar metal welds made between 9 pct Cr P91 alloy and 2.25 pct Cr T/P24-type weld metal has been investigated. Sections of multi-pass fusion welds were analyzed in their as welded condition and after PWHTs of 2 and 8 hour duration at 1003 K (730 °C). Thin foil specimens and carbon extraction replicas have been examined in transmission electron microscopes in order to identify precipitate phases and substantiate their distributions in close proximity to the fusion line. The findings of these studies confirm that a carbon-depleted region develops in the lower alloyed weld material, adjacent to the weld interface, during thermal processing. A corresponding carbon enriched region is formed, simultaneously, in the coarse grain heat affected zone of the P91 parent alloy. It has been demonstrated that carbon depletion from the weld alloy results in the dissolution of M7C3 and M23C6 chromium carbides. However, micro-alloying additions of vanadium and niobium which are made to both the P24 and P91 alloys facilitate the precipitation of stable, nano-scale, MX carbonitride particles. This work demonstrates that these particles, which are of key importance to the strength of ferritic creep resistant alloys, are retained in carbon-depleted regions. The microstructural stability which is conferred by their retention means that the pernicious effects of recrystallization are largely avoided. 相似文献
17.
Ahmad Lutfi Anis Mahesh Kumar Talari Izzul Adli Mohd Arif N. Kishore Babu Muhammad Hussain Ismail G. D. Janaki Ram 《Transactions of the Indian Institute of Metals》2017,70(3):685-690
Strength and ductility of fusion zone of metastable β titanium alloy welds can be improved by choosing suitable fillers. This paper reports the effects of using CP-Ti filler on the microstructural and mechanical properties of Ti-15-3 weldments. Full penetration autogenous and CP-Ti filler welds were produced by pulsed gas tungsten arc welding. X-ray diffraction analysis revealed small amounts of α-Ti phase in the diffraction pattern obtained for welds prepared using CP-Ti filler. Transmission electron microscopy analysis showed presence of grain boundary and intragranular α in the fusion zone of the welds prepared using CP-Ti filler. The welds prepared with CP-Ti filler showed higher hardness, higher UTS and lower % strain compared to autogenous welds. 相似文献
18.
Daniel H. Bechetti John N. DuPont John J. deBarbadillo Brian A. Baker 《Metallurgical and Materials Transactions A》2014,45(7):3051-3063
Thermodynamic and kinetic modeling were used to determine appropriate heat treatment schedules for homogenization and second phase dissolution in INCONEL® alloy 740H® (INCONEL and 740H are registered trademarks of Special Metals Corporation) fusion welds. Following these simulations, a two-step heat treatment process was applied to specimens from a single pass gas tungsten arc weld (GTAW). Scanning electron microscopy (SEM) has been used to assess the changes in the distribution of alloying elements as well as changes in the fraction of second phase particles within the fusion zone. Experimental results demonstrate that adequate homogenization of alloy 740H weld metal can be achieved by a 1373 K/4 h (1100 °C/4 h) treatment. Complete dissolution of second phase particles could not be completely achieved, even at exposure to temperatures near the alloy’s solidus temperature. These results are in good agreement with thermodynamic and kinetic predictions. 相似文献
19.
Laser butt welds were fabricated in a titanium alloy (Ti-6A1-4V, AMS 4911-Tal0 BSS, annealed) using a Control Laser 2 kW CW
CO2 laser. The relationships between the weld microstructure and mechanical properties are described and compared to the theoretical
thermal history of the weld zone as calculated from a three-dimensional heat transfer model of the process. The structure
of the weld zone was examined by radiography to detect any gross porosity as well as by both optical and electron microscopy
in order to identify the microstructure. The oxygen pick-up during gas shielded laser welding was analyzed to correlate further
with the observed mechanical properties. It was found that optimally fabricated laser welds have a very good combination of
weld microstructure and mechanical properties, ranking this process as one which can produce high quality welds. 相似文献
20.
Microstructural evolution of AZ31 magnesium alloy welds without and with the addition of titanium powders during resistance
spot welding was studied using optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM).
The fusion zone of AZ31 magnesium alloy welds could be divided into columnar dendritic zone (CDZ) and equiaxed dendritic zone
(EDZ). The well-developed CDZ in the vicinity of the fusion boundary was clearly restricted and the coarse EDZ in the central
region was efficiently refined by adding titanium powders into the molten pool, compared with the as-received alloy welds.
A microstructural analysis showed that these titanium particles of approximately 8 μm diameter acted as inoculants and promoted
the nucleation of α-Mg grains and the formation of equiaxed dendritic grains during resistance spot welding. Tensile-shear testing was applied
to evaluate the effect of titanium addition on the mechanical properties of welds. It was found that both strength and ductility
of magnesium alloy welds were increased after the titanium addition. A TEM examination showed the existence of an orientation
matching relationship between the added Ti particles and Mg matrix, i.e.,
[ 0 1[`1]0 ]\textMg // [ 1[`2] 1[`3] ]\textTi \textand ( 000 2 )\textMg // ( 10[`1]0)\textTi \left[ {0 1\bar{1}0} \right]_{\text{Mg}} // \, \left[ { 1\bar{2} 1\bar{3}} \right]_{\text{Ti}} \,{\text{and}}\,\left( {000 2} \right)_{\text{Mg}} // \, ( 10\bar{1}0)_{\text{Ti}} in some grains of Ti polycrystal particles. This local crystallographic matching could promote heterogeneous nucleation of
the Mg matrix during welding. The diameter of the added Ti inoculant should be larger than 1.8 μm to make it a potent inoculant. 相似文献