金屬材料在一定程度之機械加工，如深抽、壓延等製程之後，需對其進行適當之熱處理，來達到回復其機械性質之目的。傳統熱處理方法以長時間及高溫之持溫過程為必要手段，因此難以避免耗費大量能源與冗長時間；另外傳統熱處理設備必須依照各種工件的外型及尺寸來建置，亦會佔據大量廠房空間，也因此傳統熱處理手法無論在節約能源或者小型化的角度來看已有檢討改進的空間。
7075鋁合金為熱處理型鋁合金系統中強度最高的材料之一，主要應用在航空材料及高強度的運動器材等，其可藉由一系列之熱處理來達到所需的特性需求。本研究選用7075鋁合金經冷加工深抽之硬線，為避免直流電(DC)之正負端差異性，以交流電(AC)進行實驗，探討通電熱處理效應對線材微觀組織與拉伸性質之影響，並進一步與經傳統熱處理部分退火之線材作對比。
研究結果顯示，7075鋁合金硬線經過交流電(AC)通電熱處理後，可在甚短的時間內直接獲得再結晶晶粒。由微硬度測試可得知，經由交流電(AC)通電熱處理之材料整體呈現均質無方向性的微硬度值(Hv)分佈。在拉伸性質方面，硬線經適當之通電條件後，可大幅提升其延性與加工硬化率，有利於材料之後續加工；拉伸測試過程，有動態應變時效(DSA)現象，拉伸應力應變曲線會有不穩定之鋸齒狀抖動現象，應是材料之析出強化相分解(固溶化)所致。而將經通電處理後之材料，靜置於室溫中，會有自然時效的現象：在微硬度值(Hv)方面，會隨時間變化而緩慢上升；拉伸強度方面，會隨著時效時間增加而趨近一穩定峰值；總延伸率(TE)方面，則維持在一定水準(約10％)之上。此與經長時間傳統熱處理部分退火後之線材作比對，亦有近似的現象。

When metals pass through certain degree of cold-working, for instance, deep drawing or rolling, we must apply them to some proper heat treatment for recovering their mechanical properties. Nevertheless, traditional heat treatment procedure accompanies with long time and high temperature, which means high energy cost. Also, traditional heat treatment facilities always take up much space and are restricted by shape and size of the work pieces. In consequence, from a point of view on energy-saving or miniaturization, we could do something advances on heat treatment techniques.
7075 aluminum alloy, one of the highest strength heat-treatable aluminum alloys, which applied generally in aerospace and sporting goods, can be treated with a series of heat treatment to improve mechanical properties. In this research, we use AC current to avoid directional difference with DC current and try to figure out effects of heat treatment by electrical current on microstructures and tensile properties of 7075 aluminum alloy, compared with long-time traditional partial annealing heat treatment.
The results show that we can directly get recrystallization grains from cold-worked 7075 aluminum alloy specimens after short-time applications of AC electrical current. From micro-hardness tests, material are homogeneous in hardness value without directional difference .When it comes to tensile properties, with proper conditions, AC electrical current can greatly improve the ductility and work-hardening rate of cold-worked 7075 aluminum alloy lines, which are beneficial for the following machining. Tensile tests show dynamic strain aging (DSA) in tensile stress-strain curves with a lot of serrations after electrical current loading. The phenomenon may be correlated with solute atoms solving into the matrix (solutionizing). And it comes with nature aging when we put specimens quietly in room-temperature atmosphere after electrical current loading. With the increasing time, micro-hardness value (Hv) will rise slowly, tensile strength comes to a steady value, and total elongation (TE) is maintained above a certain degree (about 10%). In this research, there are also similar effects upon specimens with long-time traditional partial annealing heat treatment.

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