Electron Beam Melting and Improvement of Mechanical Properties of Pure Tantalum

主要从基本拉伸强度、力学性能及其与温度和应变率的关系等工程角度，实验研究了温度和应变速率对电子束熔炼纯钽板材拉伸屈服和流动的影响。在某些特定的拉伸测试和退火条件下，可以看到电子束熔化的钽的急剧预测屈服行为。拉伸塑性流动的临界温度约为0.15T/Tm，略高于粉末冶金纯钽的0.12T/Tm。在最高应变速率下的均匀伸长率测量中，在250K以下观察到明显的脆性，在300-250K的温度范围内，电子束熔化的纯钽出现了韧性到脆性转变。在低于380K的温度下，根据纯钽的屈服或流动得到的激活能和激活体积与粉末冶金技术生产的纯钽的测量值几乎相同。

Effect of the temperature and strain rate on the tensile yielding and flow of pure tantalum plate, produced by electron beam melting method, was experimentally studied mainly from an engineering viewpoints of fundamental tensile m, mechanical properties and their temperature and strain rate dependency. Sharply projected yielding behaviors were here seen for electron beam melted tantalum under certain specified tensile testing and annealing conditions. Critical temperature for the temperature dependence of the tensile plastic flow was about 0.15 T/Tm which was slightly higher as compared to 0.12 T/Tm of pure tantalum produced by powder metallurgy.Distinctive brittleness was observed below 250 K regarding the measurements of the uniform elongation for the highest strain rate conditions and ductile to brittle transition was seen for the electron beam melted tantalum at the temperatures ranging from 300 to 250 K.Activation energy and activation volume obtained at temperatures below 380 K in accordance with the yielding or flow of pure tantalum were almost the same as those values measured regarding pure tantalum produced by power metallurgical technology.