Steelisvaluedforitsreliability, butnotwhenitgetscold. Mostformsofsteel __26__ becomebrittle （脆的）attemperaturesbelowabout -25℃ unlesstheyaremixedwithothermetals. Now, though, anoveltypeofsteelhasbeendevelopedthatresists __27__ atmuchlowertemperatures, whileretainingitsstrengthandtoughness—withouttheneedforexpensive __28__.
Steel'sfragilityatlowtemperaturesfirstbecameamajorconcernduringtheSecondWorldWar. AfterGermanU-boatstorpedoed （用鱼雷攻击）numerousBritishships, a 2,700-strongfleetofcheap- and-cheerful "Libertyships" wasintroducedtoreplacethelostvessels, providingalifelineforthe __29__ British. Butthesteelshellsofhundredsoftheships __30__ intheicynorthAtlantic, and 12 brokeinhalfandsank.
Brittlenessremainsaproblemwhenbuildingsteelstructuresincoldconditions, suchasoilrigsintheArctic. Soscientistshave __31__ tofindasolutionbymixingitwithexpensivemetalssuchasnickel.
YuujiKimuraandcolleaguesinJapantriedamorephysical __32__. Ratherthanaddingothermetals, theydevelopedacomplexmechanicalprocessinvolvingrepeatedheatingandveryseveremechanicaldeformation, knownastempforming.
Theresultingsteelappearstoachieveacombinationofstrengthandtoughnessthatis __33__ tothatofmodemsteelsthatareveryrichinalloycontentand, therefore, veryexpensive.
Kimura'steamintendstouseitstempformedsteeltomakeultra-highstrengthparts, suchasbolts. Theyhopetoreduceboththenumberof __34__ neededinaconstructionjobandtheirweight—byreplacingsolidsupportswith __35__ tubes, forexample. Thiscouldreducetheamountofsteelneededtomakeeverythingfromautomobilestobuildingsandbridges.
A）abruptly
B）additives
C）approach
D）ardently
E）besieged
F）channel
G）comparable
H）components
I）cracked
J）fractures
K）hollow
L）relevant
M）reshuffled
N）strived
O）violent